chapter 22 pests and pesticides: growing...

Ron Rosmann is not a revolutionary; he’s an Iowa farmer. Likemany of his cohorts, though, he is sowing the seeds of a revolu-tion in farming. For years Rosmann, like other corn and soybean

farmers, believed that without chemical pesticides on his farm, he’dbe out of business. Pesticides are chemical substances that kill insects,weeds, and a whole assortment of organisms that reduce crop output.

In the 1980s, Rosmann visited a couple of farmers that grew cropswithout pesticides. Much to his surprise, their fields looked great.There were few weeds and insects. Encouraged by what seemed animpossibility, Rosmann began to experiment with alternatives to pes-ticides the next year. On his farm, weeds were the biggest problem, and

Pests and Pesticides:Growing CropsSustainablyChemical Pesticides

Controlling Pesticide UseIntegrated PestManagement: ProtectingCrops SustainablySpotlight on SustainableDevelopment 22-1:Indonesia Turns toBiological Pest Control

22.3

22.2

22.1

CHAPTER OUTLINE

CHAPTER 22

What we do for ourselves resides with us. What we do forothers and the world remains and is immortal.

—Albert Pine

496

CRITICAL THINKING

ExerciseA newspaper reported that a pesticide com-monly found in small amounts on fruits andvegetables caused cancer in mice. Food safetyadvocates were quoted in the article as sayingthat the pesticide should be banned. EPA offi-cials argued that the pesticide was safe be-cause their calculations showed that it wouldonly cause one additional case of cancer permillion people in the population each year.How would you analyze this issue? What criti-cal thinking rules are necessary?

herbicides (chemicals used to kill them) were a bigexpense. By using techniques he had seen the yearbefore, Rosmann found that he could virtuallyeliminate herbicides. In the 9 years that followed,he used herbicides only once, and then in smallamounts because he had mistakenly let weeds getout of control. Today, Rosmann saves $4,000 to$5,000 a year on herbicides. Much to his surprise,his crop yields have gone up. In other words, he’sgrowing more food per acre at a lower cost.

Rosmann’s efforts are a prime example of sus-tainable development. They are good for people,the environment, and the economy. Unlike Ros-mann, farmers in the industrial countries collec-tively spend billions of dollars on chemicalpesticides. To them, weeds and other pests are animpediment to efficient farming. They reduce pro-duction and profits.

Each year weeds, insects, bacteria, fungi,viruses, birds, rodents, mammals, and other or-ganisms—pest species—consume or destroy anestimated 52% of the world’s food production (thisincludes both preharvest and postharvest losses).The highest rate of destruction occurs in the trop-ics and subtropics, where because of favorableyear-round climate, as many as three crops aregrown each year on the same field. The warmweather and long growing season create optimalconditions for crop-eating insects.

Crop destruction from pests is high even inthe more developed nations, despite elaborate andcostly control strategies. In North America, for in-

stance, preharvest losses are estimated to be about31%, and postharvest losses amount to 9% of whatis left. Together, about 40% of annual U.S. pro-duction is lost to various pests. Some of the mostcommon insect pests in the United States and theirranges are shown in FIGURE 22-1.

Similar losses are reported in other more de-veloped countries. In a world where about 20% ofthe people are malnourished, such losses are tragic.The silver lining behind this ominous cloud, how-ever, is that efforts to reduce losses through pestcontrol could help increase food supplies. As you willsee in this chapter, pest control must be embarkedon judiciously. It requires a careful analysis of the so-cial, economic, and environmental costs of allstrategies—and the use of sustainable strategies.

To help set the stage for the discussion of sus-tainable pest management, this chapter beginswith a discussion of the conventional pest controlstrategies and the many environmental problemsthat make them unsustainable. It ends with a dis-cussion of the many options, including those pur-sued by Ron Rosmann, for controlling pestseconomically and in a socially and environmentallysustainable manner.

Chemical PesticidesIn China over 3,000 years ago, farmers controlled locusts byburning infested fields. In the ancient Middle East, openditches were used to trap immature locusts. In 1182 CE, Chi-nese citizens were required to collect and kill locusts in aneffort to control an outbreak. Such measures involving directhuman intervention are often called cultural controls.

Over the years, many farmers have also tried varioustoxic chemicals. Early chemical pesticides, known as first-generation pesticides, were simple but sometimes highlytoxic preparations made of ashes, sulfur, arsenic compounds,ground tobacco, or hydrogen cyanide. Lead, zinc, and mer-cury compounds were also used. In Greece, for instance,farmers used arsenic, sulfur, caustic soda, and olive oil to con-trol crop pests. Today, few of the first-generation pesticidesremain in use. Most proved to be too toxic to people or in-effective. Many were environmentally persistent. Many of thecompounds used 50 to 60 years ago still contaminate soils.

KEY CONCEPTSPest control measures have been used for centuries. Earliesttechniques included cultural controls, such as burning fields tokill locusts, and chemical controls, the use of toxic chemicals tokill insect pests. Early chemicals have been abandoned becausethey were toxic, ineffective, or environmentally persistent.

22.1

497

498 PART V. Learning to Live with the Earth’s Carrying Capacity

Modern Chemical PesticidesIn 1939, the Swiss chemist Paul Müller discovered the in-secticidal properties of a synthetic organic compound calledDDT (dichlorodiphenyltrichloroethane). This discoveryushered in a new era of chemical control. DDT became thefirst in a long line of second-generation pesticides, syn-

thetic organic pesticides. For the 25 years following its de-velopment, DDT was viewed by many as the savior of hu-mankind, for it was quite lethal to insect pests and thusincreased crop yield. Since DDT was relatively inexpensiveto produce, its use became widespread. In 1944, in fact,Müller was awarded a Nobel prize.

Over the years, thousands of new chemical pesticideshave been synthesized and tested. Today, ac-cording to the U.S. EPA, 900 different substancesare used in over 33,000 commercial formula-tions of herbicides, insecticides, fungicides, miti-cides, and rodenticides, with one goal in mind:to reduce pests to tolerable levels. Some pesti-cides, including DDT, are broad-spectrum pes-ticides that attack a wide variety of organisms;others are narrow-spectrum pesticides, usedin controlling a few pests. FIGURE 22-2 showsthe pesticide use in the United States since 1980.

KEY CONCEPTS

Types of Chemical Pesticides Synthetic chem-ical pesticides fall into three chemical families:(1) chlorinated hydrocarbons (organochlorines),(2) organic phosphates (organophosphates),and (3) carbamates.

The first group to be developed, the chlo-rinated hydrocarbons, is a high-risk group thatincludes DDT, aldrin, kepone, dieldrin, chlor-dane, heptachlor, endrin, mirex, toxaphene, andlindane. All of these have been banned or dras-tically restricted or are being considered for suchactions because of their ability to cause cancer,birth defects, neurological disorders, and dam-age to wildlife and the environment. Chlori-nated hydrocarbons are extremely resistant tobreakdown, persist in the environment, arepassed up the food chain (biomagnified), and re-main for long periods in body fat. As you will seelater in this chapter, a pesticide banned in theUnited States may still be found on food im-ported from countries where no bans are inplace.

The second group, the organic phosphates,consists of chemicals such as malathion andparathion. These pesticides, while still toxic,break down much more rapidly than chlorinatedhydrocarbons. The chlorinated hydrocarbonDDT, for example, has a half-life in the environ-ment of a couple of years; parathion, an organicphosphate, has a half-life of a couple of days.

The first synthetic organic chemical used as apesticide was a chemical called DDT, whose dis-covery ushered in a new era of synthetic chemi-cal pesticides. Chemical pesticides are eitherbroad-spectrum substances that kill a variety ofpest species or narrow-spectrum chemicals thatare effective against one or a few pests.

Grasshopper

Gypsy mothcaterpillar

European red mite

Pink bollworm

Ranges overlap Boll weevil

FIGURE 22-1 The geography of major pests. These maps of the United Statesshow the most prominent insect pests and where they are found.

CHAPTER 22: Pests and Pesticides: Growing Crops Sustainably 499

The organic phosphates are water soluble and are ex-creted in the urine. Because they are water soluble, they areless likely to bioaccumulate (Chapter 18). Despite their ben-efits, the organic phosphates are still of great concern, for hu-mans exposed to even low levels may suffer an assortmentof health effects such as drowsiness, confusion, cramps, di-arrhea, vomiting, headaches, and difficulty breathing. Higherlevels cause severe convulsions, paralysis, tremors, coma,and death.

The third group, the carbamates, are widely used to-day as insecticides, herbicides, and fungicides. One of themost common is carbaryl (commonly known as Sevin). Asa group, the carbamates are, like the organic phosphates,less persistent than the chlorinated hydrocarbons, remain-ing a few days to 2 weeks after application. They are alsowater soluble and do not bioaccumulate. Carbamates arenerve poisons, as are the chlorinated hydrocarbons and or-ganic phosphates. Although they are environmentally saferthan their predecessors, carbamates have been shown tocause birth defects and genetic damage.

Organophosphates and carbamates have one key ad-vantage over the chlorinated hydrocarbons— their lack ofpersistence. This means that they kill their pests and then dis-appear within a few days or weeks. Unfortunately, they aremuch more toxic to humans than the chlorinated organics.They enter the body rapidly through the skin, digestive sys-tem, and lungs and therefore can be harmful to people whoapply them to crops and to people who live nearby.

Although chlorinated hydrocarbons, organic phosphates,and carbamates are the three main types of pesticides in usetoday, they are not the only ones. Two others worth notingare the triazines (TRY-ah-zeens), a relatively harmless fam-ily of chemical herbicides, and the pyrethroids (PIE-rith-roids), a group of natural and synthetic insecticides, alsorelatively nontoxic to humans.

KEY CONCEPTS

Growth in the Use of ChemicalPesticidesApproximately 2.4 million metric tons (2.68 million tons) ofchemical pesticides are used annually throughout the world,approximately 22% in North America and about 57% in Eu-rope and other more developed nations. The remaining 21%is used primarily in less developed countries. The UnitedStates is a leading agricultural nation and a leader in pesti-cide use. In fact, about one-fifth of all pesticides used in theworld each year are applied to U.S. crops. Of these pesti-cides, 10% are insecticides for insect control, 46% are her-bicides for weed control, 7% are fungicides, and the remaining37% include nematicides, fumigants, rodenticides, mollus-cicides, and fish/bird poisons.

KEY CONCEPTS

OveruseAccording to University of Illinois entomologist Robert Met-calf, author of a standard college textbook on pest manage-ment, farmers apply more than twice the pesticide they need.Adding to the unnecessary environmental contamination area cadre of misinformed homeowners who apply about one-tenth of all U.S. chemical pesticides on gardens, lawns, andtrees in higher amounts per acre than farmers do. Rains washexcess pesticides into sewers, streams, and other water bod-ies. Soils exposed to heavy applications of pesticide oftensuffer because beneficial bacteria are destroyed. Withoutbacteria, grass clippings decay very slowly, creating a layerof undecomposed material called thatch. Thatch buildupon lawns is believed to be one byproduct of excessive useof pesticides.

Individuals not only apply pesticides in excess, they of-ten take poor precautions to protect themselves when ap-plying chemicals to gardens and lawns. That is, they rarelyuse or wear gloves and face masks. As noted later in thechapter, extremely toxic pesticides are often restricted—that is, not available for homeowners to use.

KEY CONCEPTSPesticides are often applied far in excess of what’s needed by farm-ers and especially homeowners. Homeowners also often fail totake precautions to protect themselves from exposure.

The more developed nations, including the United States, are themajor consumers of chemical pesticides. In the United States,the bulk of the pesticides in use are herbicides.

Three main types of synthetic organic chemical pesticides havebeen developed over the years—chlorinated hydrocarbons,organophosphates, and carbamates. These are all neurotoxins.Carbamates are less persistent in the environment or body fatof organisms—and are thus less likely to be biomagnified inthe food chain than organochlorines. Unfortunately, they aremuch more toxic to people.

Mill

ions

of p

ound

s of

act

ive

ingr

edie

nt

0

1200

1000

800

600

Herbicides

Insecticides

FungicidesOther Conventional

Other

400

200

Year200019901980

FIGURE 22-2 A profile of pesticide popularity. This graph shows pesticide production in the United States began to decline in the 1980s and early 1990s, in part because of a shift away fromenvironmentally harmful pesticides. (Data from EPA, PesticidesIndustry Sales and Usage, May 2004.)


Biological Impacts of PesticidesPesticides constitute only about 3% of the commercial chem-icals commonly used in the United States each year. Nonethe-less, because they are released into the environment in largequantities and have the potential to alter ecosystem balanceand threaten human health, their use has created widespreadand often heated controversy.

In the 1940s, DDT and other new pesticides were ap-plied to a variety of crops, with astonishing results. DDT waseven used to delouse soldiers and civilians in World War II.DDT and other chemical pesticides proved to be fast and ef-ficient in controlling insects, weeds, and other pests. In In-dia, for example, before the use of DDT in the 1950s to controlmalaria-carrying mosquitoes, there were over 100 millioncases of malaria a year. By 1961, the annual incidence had beenreduced to 50,000. Since then, the national eradication pro-gram has suffered numerous problems and the incidence ofmalaria has increased dramatically. In 2009, for instance,there were 1.5 million cases but only 1,144 deaths, accordingto the World Health Organization (WHO).

Pesticides also allowed farmers to respond quickly topest outbreaks, thus avoiding economic disaster. Pesticideswere relatively cheap and easy to apply, and their use resultedin substantial financial gains as yields increased. Some in-secticides, such as DDT and dieldrin, persisted long after ap-plication, giving extended protection. The persistence ofthese pesticides, in fact, was thought to be one of their ma-jor advantages, for one application could have lasting effects.

The successes of the early phase led to a rapid expansionin pesticide production and use. During this period, re-searchers developed many new pesticides. In the ensuingyears, however, many problems started to emerge.

KEY CONCEPTS

Destroying Natural Pest Controls and Beneficial InsectsOne of the most troubling problems is that pesticides, es-pecially broad-spectrum chemicals, often destroy naturalbiological pest controls—that is, insect predators and para-sitic insects that naturally help control pests and potentialpests. The loss of these beneficial insects (predators, for ex-ample) may result in a proliferation of pest species. In fact,some insect species that were previously benign suddenly in-crease in number and begin creating a need for additional pes-ticides. Agronomists call this population explosion of newpests an upset.

A classic example of such an upset took place in Cali-fornia. Spider mites, once only a minor crop pest, have be-come a major pest because of the use of pesticides that killedoff many of their natural enemies, which were more sensi-tive to the sprays. Today, mites cause twice as much damageas any other insect pest in California and cost farmers (in dam-age and control) five times what they cost 35 years ago. Twoof modern farming’s most costly pests, the cotton bollworm

The initial success of DDT led to a rapid increase in pesticide useand in the number of new chemical pesticides. Problems soonbegan to emerge, though.

and the corn-root worm, were minor problems 50 to 60 yearsago, before widespread pesticide use reduced their naturalpredators. In the United States, one-third of the nation’s 300most destructive insect pests are secondary pests—that is, in-sects that once caused little or no trouble at all.

Pesticides also destroy other beneficial insects, such ashoneybees, which play an important role in pollination.About one-third of the food we eat comes from plants pol-linated by insects. The honeybee is responsible for 80% of thepollination, according to the USDA. Honeybees pollinateU.S. crops (mostly fruits, nuts, and vegetables) annuallyworth an estimated $15 to $20 billion a year in 2010, the lat-est data available. Apple orchards are particularly hard hit.Honey produced by honeybees was valued at $208 million,down from $225 million in 2003. Captive honeybee coloniesare on the decline. Since 1947, they have fallen from 5.9million to 2.9 million in 2007. Numerous factors are likelyresponsible for the decline, including pesticide poisoning.Honeybee colonies are also being destroyed by parasiticmites that suck the blood from adult bees. Mites are trans-mitted by Africanized honeybees and other species. Lossesare also attributed to habitat loss, and even habitat modifi-cations. In 2006, some beekeepers began reporting massivedie-offs of bees. Each year, they reported losing 30% to90% of their hives, compared to 15%, a fairly typical annualloss. Researchers believe that this may be the result of para-sites, an unknown virus, a bacterium that attacks the gut,pesticides—and very likely a combination of these factors.Bees are under more stress due to many factors like habitatloss, which could weaken their immune systems, makingthem more vulnerable to mites and other organisms.

KEY CONCEPTS

Creating Genetically Resistant Pests Another unantici-pated effect of pesticide use has been the dramatic increasein genetically resistant insects. Because of genetic diver-sity (Chapter 6), a small portion of any insect population(roughly 5%) is genetically resistant to a pesticide. That is,it is not killed by a normal application (FIGURE 22-3). Whyare they resistant? They may contain enzymes, for example,that destroy or detoxify the poison. The presence of these en-zymes is a product of their unique genetic makeup. There-fore, an initial application of pesticides will kill all but thegenetically resistant members of a pest population. Althoughthese survivors do little damage at first, over time they re-produce and form a sizable population, which can cause sig-nificant crop damage.

As farmers encountered genetic resistance, they beganto try new approaches. The first strategy was to increase theamount of pesticide. Because of genetic resistance, this so-lution is effective only in the short term. Why? Even thoughthe higher dose wipes out the majority of the insect pests, it

One major impact of pesticides is that they often kill natural pestcontrol agents such as predatory insects that are more sensitiveto pesticides. This unleashes the growth of pest populations. Pes-ticides also kill other beneficial insects such as pollinators.


invariably leaves behind a small subpopulation that is ge-netically resistant to the increased dose. They soon proliferateand cause farmers to apply even more, creating a vicious ad-dictive cycle that many observers call the pesticide treadmill.When DDT and other insecticides were first introduced intoCentral America, cotton fields were sprayed eight times eachgrowing season; today, because of genetic resistance, 30 to40 applications are typical.

The second strategy was the development of new pes-ticides. However, scientists found that it was expensive tocreate pesticides and that the insects developed genetic re-sistance to these new chemicals almost as quickly as theywere released.

Genetic resistance to DDT was first reported in 1947by Italian researchers. In 2010, approximately 572 insectspecies were resistant to at least one form of pesticide upfrom 557 in 2007 (FIGURE 22-4). Over 20 of the world’s worstpests are now resistant to most types of insecticide. Moreover,farmers are finding that crop diseases and weeds are also de-veloping resistance to the very chemicals that are used tocontrol them. Worldwide, 354 plant pathogens (organismsthat cause disease) and 350 weeds have developed resistanceto at least one pesticide, up from 230 and 315 in 2007.

Since the introduction of DDT, insects have never met achemical pesticide they couldn’t defeat. What is more, de-spite the increased application of chemical pesticides, an-nual losses due to pests have continued to climb. Althoughinsecticide use has increased 10-fold since World War II,crop damage has doubled. Today, not only do insects take alarger percentage of the U.S. harvest than they did before theintroduction of DDT, but damage from fungi and weeds isclimbing as well.

KEY CONCEPTSPesticide use results in the formation of genetically resistant pestspecies. Higher doses and new pesticides, used to combat them,only worsen the situation by creating even more resistant species.

Damage to Fish and WildlifeMany chemical pesticideshave proved harmful to non-target species: birds, fish, andother animals. Survival ratesin newly hatched trout in up-state New York, for example, were depressed by DDT that hadbeen applied to nearby forests. Insect- and worm-eatingbirds also perished in areas where aerial spraying of insec-ticide had occurred. As a result of widespread pesticide use,populations of many birds plummeted.

The manufacturers of pesticides argued that the chem-icals were found in only minute concentrations in the envi-ronment and could not be the cause of declining populationsof fish and wildlife. Numerous experimental studies, however,showed that certain persistent pesticides—even when pres-ent in small amounts in the environment—could drasticallyaffect the reproduction and survival rate of birds and other an-imals through biomagnification, described in Chapter 18.

Studies showed that although DDT and DDE (a toxicbreakdown product of DDT) levels in aquatic ecosystemswere quite low, concentrations were higher in producers andstill higher in consumers because of biomagnification. Fish-eating birds, the consumers at the top trophic level, had thehighest concentrations of these chemicals. Although theselevels were not lethal to adults, they impaired reproduction.DDT and DDE reduced the deposition of calcium in theeggshells of birds that feed on fish and of other birds. Thislist includes peregrine falcons, brown pelicans, cormorants,bald eagles, gulls, and ospreys. Of the two compounds, bi-ologists discovered that DDE posed the greater physiologi-cal threat to birds, in part because it persisted longer. Reducedeggshell calcium levels create a thinner, more fragile shell thatcracks easily during incubation. As a result of widespreadDDT contamination, many predatory populations werenearly wiped out. In one study of bald eagle reproduction,North Dakota State University zoologist James Grier showedthat the number of young per nest in northwestern Ontariodeclined by about 70% between 1966 and 1974.

The newer pesticides are also harmful to fish and wildlife.In the United States, more than 97 million kilograms (213 mil-lion) pounds of chemical pesticides are used on lawns (both

FIGURE 22-3 Pesticide resistance. A tobacco budworm crawlsthrough deadly DDT unaffected. Because of genetic resistance,many other species are unaffected by the toxic chemicals designedto kill them.

Num

ber

of s

peci

es

0

600

500

400

300

200

100

Year1990 20101980 2000197019601950

Insects

Weeds

Diseases

FIGURE 22-4 Pesticide resistance. This graph shows the numberof species of insects, plant pathogens (disease organisms), andweeds that are resistant to at least one pesticide.

GO GREEN

Use organic and natural pestcontrol measures on gardensand lawns.


private and commercial), gardens, and golf courses. One pes-ticide, diazinon (die-AS-eh-non), was once commonly usedon sod farms and golf courses throughout the United Statesto control insects. In 1984, three fairways were treated withdiazinon in Hempstead, New York. In the 2 days followingtreatment, 700 Atlantic brant geese, 7% of the state’s entirepopulation, died of acute diazinon poisoning.

Diazinon was also used to treat nine fairways at a golfcourse in Bellingham, Washington. After application, thearea was irrigated to decrease pesticide concentrate on thesurface. Nevertheless, 85 American wigeon ducks perishedafter eating grass on one of the treated fairways on the dayof application.

In 1988, the EPA banned the use of diazinon on golfcourses and sod farms because of similar incidents. It is stillavailable for use in other outdoor areas. Although it contin-ues to kill wildlife, especially birds, mortality rates are downnow that it is no longer used on golf courses and sod farms.

Birds have also been dramatically affected by the use ofgranular carbofuran (car-bow-FUHR-an), which was de-veloped in 1970 by the FMC Corporation of Philadelphia.Farmers throughout the United States use carbofuran toeradicate nematodes and insects from corn, rice, and othercrops. Although carbofuran apparently poses no threat tohumans when applied to crops, it is lethal to songbirds. Infact, a songbird can die after ingesting a single granule.

In 1989, EPA records showed that about 2 million birdswere dying of carbofuran poisoning each year. In 1990, morethan 200 songbirds were poisoned in eastern Virginia nearthe Rappahannock River. FMC Corporation acknowledgeda problem but faulted the farmers for misusing carbofuranor for mishandling it by spilling it.

In 1991, FMC issued new instructions for the use ofcarbofuran. Still suspicious, citizens in Virginia decided tomonitor the results of that year’s pesticide application on360 hectares (900 acres) of treated farmland. They found62 bird carcasses, 10 sick birds, and 47 feather spots (indi-cating a bird had died but been eaten by a scavenger) on thefield. Many more birds could have died outside the studysite. Considering that hundreds of thousands of hectares offarmland in the state had been treated with carbofuran thatspring, it was estimated that tens of thousands of birds prob-ably died from the pesticide.

In 1991, the state of Virginia banned the use of carbo-furan, and since that time, it has been banned nationwide bythe EPA. Though the ban will likely have a positive impacton birds, it is not faultless. Export of carbofuran will continueand will probably increase to make up for shrinking do-mestic sales. To learn more about this and other pesticides,you can log on to Beyond Pesticides’ website (http://www.beyondpesticides.org).

KEY CONCEPTSPesticides poison fish, birds, and other species outright andalso biomagnify in the food chain. Thus, seemingly low con-centrations in the environment can result in very high levels inorganisms in the uppermost trophic level, which may impair re-production.

Human Health Effects Early studies showed the presenceof DDT in fish, beef, and other foods consumed by humans.DDT also appeared in the fatty tissues of seals and Eskimosin the Arctic, far from its point of use, indicating that it wastraveling in the atmosphere to remote parts of the globe.DDT in the atmosphere was washed from the sky by rainand passed through the food chain. It was also detected inhuman breast milk, a discovery that caused considerablealarm although the long-term effects of low levels on hu-mans remain unknown.

Although the general public is exposed to pesticides ina variety of ways, it is farm and chemical workers who areexposed to the highest levels from direct exposure to pes-ticides on the job as well, indicating widespread misuse.Workers pick up pesticides on their clothing and skinthrough accidents and negligence or by prematurely en-tering sprayed fields. In most cases, workers are poorlyprotected (FIGURE 22-5). They are often given few instruc-tions and no protective gear to minimize exposure—espe-cially in the less developed countries, where poor workersafety standards and practices and widespread illiteracyare common. In the less developed countries, workers of-ten complain of being sprayed with insecticides from hel-icopters or planes while they are working in fields and onplantations. A study in Palestine uncovered another seri-ous problem: The instructions on pesticide containers wereprinted in Hebrew, despite the fact that most of the farm-ers and farm workers read only Arabic.

In less developed countries where farm labor is abundantand worker safety provisions minimal, workers are oftenviewed as an expendable commodity. Christopher Brady,who is active in development work in Latin America andAfrica, writes, “As a result of increasing health risks to thesprayers, Tela (a Honduran subsidiary of Chiquita Brands,Inc., a U.S. company) has changed their hiring policy. Sprayersare now only hired on a 6-month contract.” They are “letgo and new ones hired before any serious health problemsmay be detected.” Workers spraying herbicides on banana

FIGURE 22-5 Farm workers at risk. Poorly protected farm work-ers are exposed to the highest levels of pesticides.

FIGURE 22-6 Pesticide drift. Pesticide sprayed fromplanes contaminates the ecosystem because much ofthe pesticide drifts away. Various avenues for the dis-persal of pesticides are shown. Average values for DDTconcentrations are indicated in parts per million (ppm)and billion (ppb). Families living near sprayed fieldsare exposed to herbicides and pesticides.


plantations are given a thin cotton mask as their only pro-tective gear. Moreover, empty barrels once containing con-centrated pesticide are often used by local villagers to holddrinking water.

Symptoms of poisoning are many. They include insomnia,nausea, and loss of sex drive. Some people exposed to pesticidescomplain of reduced powers of concentration, irritability, andnervous disorders. Spills on one’s skin may cause rashes and aburning sensation. In severe cases, death will occur.

In the United States, at least 45,000 workers are seriouslypoisoned each year, but many experts believe that this figuregrossly underestimates the number of serious poisonings.Surveys in California, for instance, show that three-fourthsof all serious poisonings go unreported. Each year 200 to 1,000people die from pesticide poisoning in the United States.Worldwide, there are at least 25 million pesticide poisoningsannually, according to the World Health Organization. Theseresult in an estimated 200,000 deaths each year, according toWorld Health Organization statistics. Pesticide poisoning alsoresults in numerous chronic and fatal illnesses. What is more,the WHO expects the number of poisonings to increase if pes-ticide use increases in the less developed countries.

Although farm and chemical workers are the groupsmost heavily exposed to pesticides, residents of rural andeven suburban areas are often exposed to potentially dan-gerous levels if they live near agricultural lands. Familiesliving near fields sprayed with herbicides and pesticides out-side Scottsdale, Arizona, for example, suffered from per-sistent headaches, cramps, skin rashes, dizziness, high bloodpressure, chest pains, persistent coughs, internal bleeding,and leukemia. Health officials are worried the most about pos-sible long-term problems from exposure.

People living near pesticide-treated fields are heavilyexposed because one-half to three-fourths of the sprayedmaterial never reaches the ground but is carried away bylight winds (FIGURE 22-6). Recent studies have also shownthat pesticide applied to one crop may be able to va-porize under sunlight and drift to neighboringcrops. Exposure may also occur through con-taminated groundwater.

In an effort to control mosquitoes, many citiesin the United States routinely spray insecticides inneighborhoods and nearby breeding areas. InFlorida, for instance, various mosquito control agen-cies argue that controlling the insect is vital to realestate interests and tourism because it minimizes therisk of encephalitis, a potentially deadly brain in-fection that is caused by an organism carried bymosquitoes. The 1990–1991 Florida encephalitis

epidemic resulted in over 130 cases and more than 10 deaths.In 2004, there were numerous reported cases and nine deaths.In 2006, 2007, and 2009, there were no reported cases of en-cephalitis in humans.

To protect residents from West Nile Virus, which is car-ried by mosquitoes, many cities have started or increasedpesticide spraying. To protect against diseases, trucks andaircraft spew out tons of pesticides while residents sleep.What long-term health impact this has, if any, is unknown.Florida wildlife officials, however, think that pesticide useis largely responsible for a 70% decline in the population ofsnook, a popular sport fish. Adding to the problem, city of-ficials use a variety of pesticides in city parks, and lawn-carecompanies and individuals douse lawns and trees with a va-riety of toxic substances, often incorrectly and without warn-ing neighbors.

Consumers may also become the victims of pesticide poi-sonings. In the summer of 1985, for instance, 1,400 peopleon the West Coast were stricken with nausea, diarrhea, vom-iting, and blurred vision after eating watermelons contaminatedwith the pesticide aldicarb illegally used by farmers. The EPApermits aldicarb for use on cotton and on vegetables that arecooked before consumption (such as beans and potatoes) butnot on crops such as watermelon whose produce is eatenwithout cooking. In 1992, 29 people were poisoned and threehospitalized in Ireland after eating cucumbers sprayed withaldicarb, also not approved for use on this vegetable. Althoughsuch instances appear to be rare, millions of people could beconsuming high levels of pesticides on fruit and vegetables,especially in poor countries such as India. Pesticide residueson these foods often exceed safe levels. While they may notcause immediate death they could contribute to long-termillnesses such as cancer.

Rain 0.1–0.3 ppb

Groundwater 0.001–0.2 ppbRivers and lakes 0.001–0.2 ppb

Fat of cows 0.5 ppm

Fat of man6–12 ppm

Trade winds 0.1–0.3 ppb


KEY CONCEPTS

The Economic Costs of Pesticide UseAlthough pesticide use helps protect crops and saves us bil-lions of dollars, pesticide use has an environmental impact.All environmental impacts have an economic cost. Humanpesticide poisonings, described in the previous section, causeillness and death, both of which exact a huge economic cost.Some pesticides have been shown to damage crops. Cropshave been destroyed by herbicides that were reportedly safeto apply. Organic farmers are finding that pesticides evapo-rate from neighboring farms, contaminating their crops. In2003, the Bush administration adopted a policy that willmake it impossible for farmers to sue manufacturers of pes-ticides that fail to live up to company claims.

Pesticides may also end up in groundwater in rural com-munities, causing a potential health risk and necessitatingcostly cleanup. The Monsanto Company, which producesherbicides, estimated that of 6 million wells in a surveyed areain the United States, 13% (770,000 wells) were contami-nated with one or more of five herbicides; 6,600 wells con-tained levels exceeding the EPA’s maximum contaminationlevel. Although the company insists that none of the herbi-cides poses a threat to health, it is offering well owners whosewater is contaminated above specified concentrations up to$2,000 a well to make corrections.

KEY CONCEPTS

Herbicides in Peace and WarForty-six percent of all chemical pesticides applied to cropsare herbicides. Although there are over 180 types of syn-thetic herbicides on the market, four products are used ingreatest quantity: atrazine, alachlor, butylate, and 2,4-D (2,4-dichlorophenoxyacetic acid). Two herbicides have receivedmost of the attention: 2,4-D and 2,4,5-T. These are nonper-sistent synthetic organic compounds similar in function toplant hormones called auxins. When sprayed on plants, 2,4-D and 2,4,5-T increase the metabolic rate of cells so muchthat plants cannot keep up with increased nutrient demandsand literally grow to death.

KEY CONCEPTSPlant auxins are hormones that stimulate plant growth. Two ofthe most widely studied herbicides are auxin-like compounds.

Pesticide use is not just a threat to human health and the en-vironment, it causes considerable economic damage.

Pesticides contaminate many foods and have been found in hu-man body tissues even in remote areas of the world, indicatingthat pesticides are globally distributed. Chemical and farm work-ers are frequently exposed to the highest levels, especially in theless developed nations. The effects of pesticide exposure rangefrom mild neurological problems to death, depending on theexposure level and type of chemical.

Peacetime Uses: Pros andCons 2,4-D and 2,4,5-Twere once widely used tocontrol brush and plantsalong roadways, power lines,and pipelines. They have alsobeen used to control poisonivy and ragweed, eliminateunwanted trees in commercial tree farms and in NationalForests, kill aquatic weeds, and rid rangelands of brush andpoisonous plants. Overall, three-fourths of these chemicalsare used for weed control on farms.

The benefits of these and other herbicides are many:1. They decrease the amount of mechanical cultivation

needed to control weeds—and thus reduce labor costs.

2. They reduce weed damage when soils are too wet tocultivate, because crops can be sprayed by plane.

3. They help farmers reduce water usage because waterescapes more rapidly from ground that has been tilledto control weeds.

However beneficial their use may be, herbicides also havemany drawbacks:

1. Some weeds have become resistant to herbicides andhave become more troublesome.

2. Some nonpest species proliferate after spraying. To getrid of them, additional herbicide or more toxic onesmay be needed.

3. When herbicides are used, farmers often reduce tillage;the weeds killed by herbicides remain on the groundand provide food and habitat for insect pests. Herbicideuse therefore may actually increase insect pest popula-tions, increasing the need for insecticides. In addition,herbicides may decrease the farmer’s incentive to rotatecrops, an effective way of reducing insect pests.

4. Herbicides may make some crops more susceptible to in-sects and disease. For example, some herbicides reducethe waxy coating on plants, change their metabolic rates,and retard or stimulate plant growth; all of these effectsmay make plants more susceptible to insects and disease.

5. Some herbicides are toxic and may cause birth defects,cancer, and other illnesses in animals.

Critics argue that integrated weed management couldreduce the use of herbicides. Such management would em-ploy special equipment such as wick applicators that applyherbicide only on weeds between rows. Wick applicatorsconsume much less herbicide than aerial spraying and cre-ate less environmental contamination. The reasonable use ofherbicides could be complemented by mechanical cultiva-tion, proper spacing of rows for healthy crops, biologicalweed controls, and crop rotation.

KEY CONCEPTSHerbicides provide many benefits but do not come without so-cial and environmental costs. Fortunately, there are many waysto reduce or eliminate herbicide use.

GO GREEN

Start an organic garden or minifarm on your college campusto provide produce to localcafes or the college foodservice.


Controversy over Wartime Use of 2,4-D and 2,4,5-T Her-bicides were used extensively in the Vietnam War in the1960s and early 1970s as defoliants: to prevent guerrilla am-bushes along roads and waterways; to deter the movementof soldiers through demilitarized zones and across the bor-der of Laos; to destroy crops that might be eaten by the en-emy; and to clear areas around camps. Three herbicidepreparations were sprayed from planes, helicopters, boats,trucks, and portable units from 1962 to 1970.

The most effective and most controversial of the herbi-cides was Agent Orange, a 50-50 mixture of 2,4-D and 2,4,5-T (FIGURE 22-7). During the war, over 42 million kilograms(93 million pounds) of Agent Orange was sprayed on the wet-lands and forests of Vietnam, decimating 1.8 million hectares(4.5 million acres) of countryside and at least 190,000hectares (470,000 acres) of farmland. Over half of the man-grove vegetation of South Vietnam (1,930 square kilome-ters, or 744 square miles) and about 5% of the hardwoodforests were destroyed. The forests alone represent about$500 million worth of wood, a supply that would last 30 years.

The prospect for these forests seems dim because hardyweed species such as cogon grass and bamboo have invadedthe deforested zones. Ecologists fear that these species maygreatly delay recovery or prevent it altogether. The NationalAcademy of Sciences estimates that defoliated mangrovesmay take 100 years to recover because the destruction wasso great that few seed sources remain. Because mangroveswamps protect coastlines from storms and because they arevital habitat for commercially important fish, numerous ef-forts are under way to replant the mangrove swamps inVietnam. The International Red Cross and the country ofVietnam for instance, invest heavily in such efforts.

Defoliants and numerous insecticides used to controlmosquitoes created an ecological disaster in Vietnam, re-sulting in the death of numerous fish and animals. In one sur-vey of a heavily sprayed forest visited years after the warended, Harvard University biologist Peter Ashton found 24species of birds and 5 species of mammals, compared with145 and 170 bird species and 30 and 55 mammal species intwo nearby forests that had not been sprayed. The total im-pact of such actions will never be known.

Agent Orange may have been the cause of serious med-ical problems that developed in soldiers and villagers through-out Vietnam. Studies suggest that health effects attributed toAgent Orange probably resulted from contaminants be-longing to a group of chemicals known as dioxins. Dioxinscause birth defects and cancer in mice and rats. Dioxin, dis-cussed in Chapter 18, is believed to be 100,000 times morepotent than the tranquilizer thalidomide, which caused manybirth defects in Europe. Soldiers from the United States andAustralia who fought in herbicide-defoliated areas and wereexposed to substantial amounts of the chemical developedsevere headaches, nausea, diarrhea, internal bleeding, chlor-acne (a severe skin rash similar to acne), and depression.

In 1970, as a result of the public outcry in the UnitedStates, the government banned the use of Agent Orange inVietnam. In 1985, 2,4,5-T was banned altogether. Use of2,4-D continues today to control hardwood trees that areconsidered weeds in commercial evergreen forests.

Vietnam veterans returning from the war also began tosuffer unusual medical disorders. A high proportion of themen have fathered offspring that were born dead or abortedprior to term, as well as infants with multiple birth defects.Other veterans have developed lymphoma, leukemia, and tes-ticular cancer.

Perhaps the most compelling evidence linking ad-verse health effects to Agent Orange came from a study car-ried out by Vietnamese doctors. They examined the rateof birth defects in the offspring of 40,000 Vietnamese cou-ples and found that women whose husbands had foughtin South Vietnam, where Agent Orange was sprayed, were3.5 times more likely to miscarry or give birth to defectivechildren than women whose husbands had remained in thenorth during the war. American scientists who studiedthe results, although expressing caution, found the studyconvincing.

Data recently released from an independent study ofmilitary veterans indicate an increased risk of elevated bloodpressure, benign fatty tumors, miscarriage, visual and skinsensitivity to light, and depression. Other evidence has im-plicated dioxin as the cause of soft-tissue sarcomas (can-cers); veterans exposed to dioxin had a rate of soft-tissuesarcomas seven times higher than normal.

In May 1984, manufacturers and Vietnam veteransreached an out-of-court settlement that established a $180-million fund for veterans and their families claiming injuryfrom Agent Orange. In 1989, seven companies that were be-ing sued by veterans for damages caused by Agent Orange

FIGURE 22-7 Spraying Agent Orange. Vietnamese jungles weresprayed with Agent Orange to clear the vegetation.


agreed to pay them $240 million. Still unconvinced that thedata showed a link between Agent Orange and these seriousproblems, the VA has reluctantly agreed to treat all Vietnamveterans, a change in policy that may be too late for many ofthe soldiers.

KEY CONCEPTS

Controlling Pesticide UseConcern over the health and environmental effects of pes-ticide use has led to a number of actions to minimize impacts,including outright bans of harmful pesticides, registration,and establishing tolerance levels on produce. This section dis-cusses these actions and their strengths and weaknesses.

Bans on Pesticide Production and UseIn the United States, cautionregarding pesticide use be-gan in 1962 with the publi-cation of the late RachelCarson’s book Silent Spring,which pointed out many ofthe real and potential im-pacts of pesticide use (FIGURE 22-8). This widely read bookis credited with touching off the controversy that resulted inincreased public awareness and research on the effects ofthe indiscriminate use of pesticides. Concern reached a peaka decade later with the near extinction of peregrine falcons,brown pelicans, cormorants, bald eagles, and other birdspecies exposed to DDT.

Faced with the growing body of evidence that illustratedthe many hazards of using chemical pesticides, environ-mentalists pushed for bans on certain pesticides. Scientistshave found that such bans have greatly benefited U.S. wildlife.The ban on DDT in the United States, for instance, has re-sulted in increases in the number of endangered bald ea-gles, brown pelicans, ospreys, and other species. Recentstudies show that DDE and DDT levels have dropped in wildpopulations and that normal reproductive rates have re-turned. Affected bird populations are recovering nicely andsome may be moved off the endangered species list.

Bans on the production and use of pesticides in theUnited States, however, are only part of the answer. Con-tinued use of pesticides outside the United States, as in thecase of carbofuran, poisons migratory species such as song-birds that winter in Central America and Mexico but spendspring and summer in the United States. In addition, muchof the produce imported into the United States has recentlybeen found to be contaminated with pesticides, many ofwhich were banned in the United States. Because one-fourthof the fruit and vegetables sold in the United States comes

22.2

Extensive use of chemical defoliants (Agent Orange) during theVietnam War has resulted in substantial environmental andhealth impacts in soldiers and their offspring. The health effectsare attributed to dioxins that contaminate the herbicide.

from foreign countries, global bans of harmful pesticidesare needed to protect human health.

Unfortunately, only 21% of all pesticides sold in the U.S.have been adequately tested for carcinogenicity. Less than 10%have been tested for their ability to cause genetic mutationsand less than 40% have been tested for their potential tocause birth defects.

KEY CONCEPTS

Registering PesticidesAnother way of controlling pesticides is the act of registra-tion, described shortly. In the United States, pesticide regis-tration was first required by the Federal Insecticide,Fungicide, and Rodenticide Act (FIFRA), a law currently ad-ministered by the Environmental Protection Agency (EPA).The FIFRA is designed to protect farmers, farm workers, thegeneral public, and the environment from new chemical pes-ticides. It does this by requiring manufacturers to test new pes-ticides for a range of effects before they can be registered for

Many environmentally harmful pesticides have been banned inthe United States in the past 30 years. Some of these pesti-cides, however, continue to be used in other countries, wherethey poison wildlife and migratory birds and contaminate cropsdestined for local markets as well as markets in the United Statesand other more developed countries.

FIGURE 22-8 Antipesticide crusader. Scientist Rachel Carsonfirst drew attention to the dangers of pesticides in her environ-mental classic Silent Spring.

GO GREEN

Lobby your college or universityfood service to use organicfruits and vegetables producedby local farmers, if possible.


use. Pesticides introduced prior to the passage of the law in1972, however, were originally not affected.

Registration is a kind of permitting process managed bythe EPA. When a company develops a new pesticide that itwants to market, it must perform a number of tests on plantsand animals to assess the potential toxicity of the chemical.Test plots are also sprayed with the pesticide to determineresidues—that is, how long the chemical remains. Thesedata are then submitted to the EPA scientists for their re-view. Taking into account the average American diet, residuelevels, and toxic effects, the EPA then determines on whichcrops, if any, the pesticide can be used.

The critical thinking skills you have learned may sug-gest a problem right away: Is the average American diet ac-curately determined? If the truth be known, the averageAmerican diet includes a great deal of red meat, chicken,and other meat products. That automatically excludes veg-etarians, however, who tend to consume large quantities offruits and vegetables. Ironically, many vegetarians who se-lect a special diet for health reasons are inadvertently ex-posed to the highest levels of pesticide—unless, of course,they consume organic produce. Organic produce includesfruits and vegetables grown without pesticides or syntheticfertilizers. Most grocery stores contain a small selection oforganically grown produce. In a number of states large gro-cery stores such as Wild Oats specialize in healthy food, in-cluding organically grown fruits and vegetables, as do manysmaller health food stores.

Pesticides are registered for general or restricted use.General use means that anyone can purchase and use them.Technically, restricted-use pesticides are to be used by li-censed applicators—farmers and lawn-care companies, forinstance.

The problem with this system is that pesticide use islargely regulated by an honor system. Labels on restricted-use products describe their legal uses, and only licensed ap-plicators can buy them; other than those limitations, there’svery little if anything to stop people from using pesticides anyway they please. The aldicarb poisonings cited earlier illus-trate one of the common problems.

In 1988, the FIFRA was amended to correct some of itsweaknesses. One of the most significant gains was a plan toregister many pesticides that had been introduced beforethe EPA took over the process in 1972. Pesticide registrationsin the 1950s and 1960s were made with very little if anysound toxicological data, say critics. Registering the over300 chemical pesticides will take many years to complete andwill be funded by fees paid by the chemical companies. Someexperts see this as a weeding-out process. They believe thatmany pesticides will be canceled as companies that are afraidtheir product won’t be approved for health and environ-mental reasons won’t invest the money needed to registerthem.

Despite this improvement, critics say that additional re-form is necessary. For example, pesticide registration doesnot currently require manufacturers to test for neurotoxic-ity—toxic effects on the nervous system, the brain, spinalcord, and nerves. To many critics, this is a glaring omission

because about half of the pesticides (especially theorganophosphates) are insect neurotoxins that could alsoaffect the human nervous system.

New research also shows that some pesticides damagethe immune system, the body’s defense against bacteria,viruses, and even cancer. Pesticide registration, however,requires no test of immune system effects—another omission,say critics. In addition, pesticide registration does not takeinto account possible synergism, the super-additive effectdescribed in Chapter 18.

Perhaps the most glaring problem, though, is that theFIFRA provides virtually no monitoring functions. Theend users are free to do as they please. They can apply asmuch pesticide as they want and can apply it whereverthey want. Moreover, there is no one to see that solutionsare mixed correctly or that equipment is working prop-erly. As a result, farmers frequently apply much more thanis needed.

Licensing and training are the only avenues availableto address this problem. To be licensed, most states requirefarmers to take a test. In Colorado, for example, farmersmust study a booklet provided by the EPA and then take anopen-book test. If they pass, they’re licensed to spray re-stricted pesticides on their fields. Critics argue that morerigorous education and testing are needed.

Governments, pesticide companies, farmers’ groups,and universities could provide additional hands-on train-ing and monitoring to be sure that pesticides are used moresafely. As mentioned earlier, programs that teach farmers tobecome better at identifying pests and monitoring pest pop-ulations in the field could decrease insecticide use and costs.Special crop scouts, such as those now in use in Indonesia,could be trained to monitor pest populations and determinewhen they have reached the threshold level. They could alsoassist farmers in finding alternative ways of controlling pests.(See Spotlight on Sustainable Development 22-1 for moreon Indonesia’s program.)

KEY CONCEPTS

Establishing Tolerance Levels and Monitoring ProduceTo help protect public health, the FIFRA also authorizes the EPAto set tolerance levels for pesticides on fruits, vegetables, andother foods. Tolerance levels are concentrations in or on foodsthat are believed to pose an acceptable health risk. For cancer,the EPA sets the concentration at a level it thinks will cause nomore than one additional cancer death in one million people.This determination is fraught with difficulty, as explained inChapter 18. Interestingly, although the U.S. EPA sets tolerancelevels for pesticides on foods, there is no limit to the numberof different pesticides that can be present. Chemical pesticides

The EPA registers newly developed and previously introducedpesticides for general or restricted use and stipulates what cropsthey can be used on, a process called registration. Many im-provements are needed in this system to make it more effective,especially more rigorous education and testing of users.


can have synergistic effects at very low levels, and little re-search has been performed to assess potential effects.

Although the EPA sets tolerance levels, it is up to the U.S.Food and Drug Administration (FDA) and state agriculturalagencies to monitor the nation’s food supply and to enforcetolerance levels. Inspectors examine fruits and vegetablesand have the authority to seize and condemn foods con-taining residues that exceed EPA levels or that contain ille-gal pesticides—but only when they are shipped from one

state to another. Inside thestates, the responsibility formonitoring food lies withstate agencies.

Both the FDA and stateagencies suffer from a com-mon problem: a chronic lackof funds and a shortage of inspectors. Given these

SPOTLIGHT ON SUSTAINABLE DEVELOPMENT

22-1 Indonesia Turns to Biological Pest Control

Indonesia is a country of islands—nearly 14,000 of them—in Southeast Asia. In 1983, this rural nation, once theworld’s leading importer of rice, succeeded in growingenough rice to feed its own people. New strains of rice, fer-tilizers, and an intricate irrigation system deserved muchof the credit for the success. In 1985, however, the noto-rious brown planthopper threatened the progress of theprevious years. This insect causes rice to dry out, rot, andfall in the field. Infestations of the insect can cause enor-mous damage.

To combat the planthopper, in 1985, the governmentdecided to try integrated pest management (IPM). It wasadvised to do so by an Indonesian entomologist, Dr. Ida Oka,who had received his Ph.D. from Cornell University underDavid Pimentel, a leading expert on natural insect control.Oka had been in charge of pest management in the late1970s and early 1980s and had implemented sound IPMfor rice and other crops. During that time pesticide use hadbeen greatly reduced, and rice yields had soared. Oka hadresigned, however, when a new minister of agriculture wasappointed. This official’s pro-pesticide policies, in whichthe government paid about 85% of the cost of pesticides tofarmers, resulted in widespread use of chemical pesticidesand clearly placed the farmers on the pesticide treadmill.This policy was largely responsible for the outbreak of thebrown planthopper in 1985.

Indonesian scientists had found that the use of pesti-cides to control the planthopper and other insects killedmany beneficial insects that preyed on the pest. One of thebeneficial insects destroyed in the spraying was the wolf spi-der, which can devour 5 to 20 brown planthoppers a day. Ifleft alone, the beneficial insects could often control theharmful ones. Researchers also found that farmers sprayedfields regularly, regardless of whether they needed it. Theoveruse of pesticides actually increased the severity of in-festations, so much so that by 1986 the country was indanger of becoming a rice importer once again.

Convinced of the danger of the continuing use of pes-ticides, the Indonesian government asked the UN Food andAgricultural Organization (FAO) to help it promote an IPMprogram. In 1986, with the help of the FAO, the government

embarked on a program to educate farmers on IPM and thedangers of pesticides. Experts ventured into the rice pad-dies, where they showed farmers how to diagnose prob-lems, calculate the ratio of good bugs to bad ones, anddecide how much damage the crop could stand without a de-crease in yield. They then taught farmers ways to reducespraying and methods to protect beneficial predatory insects.

Early results showed that IPM worked. IPM reducedpesticide use substantially. Trained farmers, for example, ap-ply one-ninth as much pesticide as they did before training,with no decrease—sometimes even an increase—in cropyield. Farmers have also learned to discern more carefullyinsect damage from fungal damage, and this helps to reducepesticide use.

The average yield on farms using pesticides was 4%lower than on fields controlled by IPM. Despite the high sub-sidies for insecticides, the farms using IPM proved moreprofitable than those sprayed more frequently. The gov-ernment saves an estimated $120 million a year on pesti-cide subsidies. Indonesia’s streams and wildlife also startedshowing signs of recovery.

The success of the pilot program in Indonesia con-vinced the government to adopt IPM as a national pestcontrol strategy. The government, in fact, banned 56 of the57 pesticides previously approved for farming in Indonesia,in order to help protect predatory insects. The governmentthen launched a massive campaign to educate Indonesia’sfarmers in IPM. In 1992, the country hired 2,000 crop scoutsto educate farmers on IPM and hoped that all farmers wouldsoon be using this method.

Since then, integrated pest management has spreadto Thailand, Bangladesh, Sri Lanka, Malaysia, India, andChina. Farmers in Indonesia who were not introduced tothe technique raised their voice. They wanted to be in-cluded in this effort to help the world move to a more sus-tainable, environmentally safe form of farming. Agriculturalexperts believe that IPM could be used on fields that pro-vide 45% of the rice for people living in southern and south-east Asia and could save millions of dollars, preserve wildlife,and protect human health without endangering high cropyields.

GO GREEN

Buy organic fruits and veg-etables, especially lettuce,beans, spinach, celery, pep-pers, apples, peaches, andpears, which are not directlysprayed with pesticides andnot peeled.


problems and the massive amount of food consumed by theAmerican public, it can be no surprise that only a small por-tion of our food is actually tested. Furthermore, examiners testonly for the presence of a handful of the pesticides that couldbe on our food. Unless you grow your own food, you are prob-ably consuming small amounts of many pesticides. In a recentstudy, more than 50% of all food in supermarkets was foundto contain detectable levels of pesticides. Only a small per-centage of domestically produced fruits and vegetables (around2%) contained residues that violated federal standards. Vio-lations in imported vegetables were more common (about 5%to 7%).

Similar problems occur in other countries. In Ireland, forinstance, the Pesticide Control Service has only 11 scien-tists to test food for the entire country. Consequently, fewfarmers are inspected, and only 2,000 food samples are testedannually.

Currently, the EPA reported that at least 45 pesticides onfood are thought to be carcinogenic at least to nonhumananimals. In 1987, the National Academy of Sciences issueda report concluding that 1 million Americans alive today willdevelop cancer as a result of pesticide contamination of theirfood—that’s one of every 250 Americans. Add to that possi-ble birth defects, miscarriages, mutations, neurological ef-fects, and other milder symptoms, and it is little wonder thatthe EPA ranked pesticides in food as one of the nation’s mostserious health concerns.

Critics of pesticide regulations argued that the toler-ance levels set for pesticide residues were inadequate be-cause they failed to take into account the special diets ofvegetarians and children.

In 1996, the U.S. Congress strengthened pesticide reg-ulations by passing the Food Quality Protection Act. It re-quires the EPA to estimate risks of pesticides from all sources,including drinking water, food, and home uses. It also requiresthe EPA to determine risk to infants and children and buildin protection for these age groups. Historically, however,critics point out that the EPA rarely revises tolerance levelswhen new scientific data about risks become available. Also,it rarely bans a pesticide if it is harmful to wildlife but not topeople.

Some additional reforms in pesticide controls were alsoincluded in the recent legislation. For example, the EPA isdirected to consider health risks other than cancer and to con-sider hormone-mimicking properties of pesticides. As notedin Chapter 18, some pollutants mimic naturally occurringhormones and can dramatically alter reproductive and otherfunctions in fish, wildlife, and perhaps even humans.

Another problem is that the chemicals that pesticides aremixed with or dissolved in may also be toxic. In fact, stud-ies of pesticides used indoors show that some of these sub-stances reach rather high levels—and remain high indoorsfor a considerable length of time after a house has beensprayed for cockroaches, ants, or other insects.

The next section shows that there is a way to greatly re-duce or even eliminate pesticide use. It is called integratedpest management. In the interim, individuals can avoid someproduce containing pesticides by growing some of their own

fruits and vegetables or by purchasing organically grownproduce. Washing fruits and vegetables can help but won’teliminate all pesticide residues. Beyond that, individuals canexercise their democratic prerogatives by writing local, state,and federal officials and asking for tougher laws to regulatepesticide registration and use.

KEY CONCEPTS

Weakening ProtectionFederal pesticide regulations have been refined over the years,providing more and more protection to people, wildlife, andthe environment. Some states have even increased protectionby passing more stringent regulations. Other states, however,are working to weaken pesticide regulations. Congress is cur-rently considering legislation that could result in more pesti-cide contamination of streams and rivers from commercialtimber operations and a host of other actions.

Integrated Pest Management:Protecting Crops Sustainably

Integrated pest management (IPM) is a new strategy of pestcontrol gaining popularity throughout the world. It dependson four sustainable means of pest control: environmental, ge-netic, chemical, and cultural. Two or more of these ap-proaches may be used simultaneously to control pests, withlittle or no damage to the environment and human health.Studies show that they also offer important economic ben-efits. Remember, as you read about the various strategiesdescribed in the following pages, the central goal of inte-grated pest control: to reduce pest populations to levels thatdo not cause economic damage, while protecting humanhealth and the environment. The goal is not to eliminatepest species entirely, which may be impossible anyway.

KEY CONCEPTS

Environmental ControlsEnvironmental control is a term used to designate a num-ber of techniques that alter the biotic and abiotic conditionsin crops, making them inhospitable to pests. Because theygenerally rely on knowledge more than on technology, thesepractices are especially suitable for less developed countries.Still, they can be equally effective if used properly in mod-ern agricultural societies.

Integrated pest management is a set of alternative strategies tocontrol pest populations at manageable levels. It offers sub-stantial social, economic, and environmental benefits and isthe cornerstone of a sustainable system of agriculture.

22.3

The EPA also sets tolerance levels—acceptable levels of pesti-cides on food—which are monitored by the U.S. Food and DrugAdministration. Unfortunately, inadequate funding prohibitsthorough sampling.


KEY CONCEPTS

Increasing Crop Diversity:Heteroculture and Crop Ro-tation In Chapter 10, we sawthat monocultures generallypromote pest and disease out-breaks. Crop diversity, on the other hand, reduces the amountof food available to any one pest and helps prevent such rapidpopulation growth. Several techniques can increase crop di-versity, among them heteroculture and crop rotation.

A farmer who plants several crops side by side in hisfield, rather than huge expanses of one crop covering, ispracticing heteroculture. This simple but effective measureworks because it provides environmental resistance to pests;that is, pest populations are often much smaller in hetero-cultures than in monocultures because there is less to eat. Inaddition, some crops harbor predatory insects that feed onpests in nearby crops. Corn and peanuts grown in adjacentfields, for instance, can reduce corn borers by as much as 80%.Part of the reason for this success may be that predatory in-sects that feed on the corn borer live in peanut crops.

Chapter 10 discussed one of the most recent and in-novative ways of intermixing crops and strip cropping (FIG-URE 22-9). In this technique, alternative strips of corn andsoybeans (or other crops), each with a dozen or more rows,are planted side by side in the same field. This not only de-creases insect pests but also increases yield because the cornprotects the soybeans from wind while the openness of thefield provides more sunlight to the corn.

Heteroculture decreases pesticide use and also providesa means of diversifying farm production from year to year.In some ways, then, it is a form of insurance. Ron Rosmann,for example, plants half of his 200-hectare (500-acre) farmin corn and soybeans. The rest he devotes to hay, pasture, cat-tle, hogs, chickens, and a tree nursery that he hopes willhelp pay for his three sons’ college educations. A bad year forcorn will not wipe him out.

Heteroculture can be practiced by home gardeners withgreat success. I have been growing vegetables in a pesticide-free garden for nearly 30 years and have had virtually notrouble with insects, in large part because I intermix species.Small patches of carrots are planted next to peas, which arenext to spinach, and so on. I also plant onions, marigolds,and other species that tend to repel pests.

Crop rotation, discussed in Chapter 18 as a means of re-ducing soil erosion and increasing soil fertility, also helpscontrol pests, for at least two reasons. First, the healthierthe soil, the healthier and more resistant the plants are to in-sects and disease. Second, it also helps hold down pest pop-ulations because it reduces food available from one year tothe next for specialized insects—those that feed on only onecrop. For instance, wireworms feed on potatoes but not al-falfa. Therefore, if potatoes and alfalfa are alternated from year

Environmental controls seek to change both the biotic and abi-otic conditions of crops in ways that reduce the growth of pestpopulations, while causing little if any damage to the crop itself.

to year in the same field, wireworm offspring that hatch inthe alfalfa patch will have little to feed on. Their numbers willdecline severely. When potatoes are planted the next year, fewwireworms will be around. Although the population mayincrease during the growing season, it will generally notreach a level that causes harm. The next year alfalfa is planted,and wireworm offspring once again perish. Gardeners can alsopractice crop rotation on a small scale to hold insects incheck.

KEY CONCEPTS

Altering the Time of Planting Some plants naturally escapeinsect pests by sprouting early or late in the growing sea-son. A good example of this adaptation is the wild radish,which sprouts early in the season before the emergence of thetroublesome cabbage maggot fly.

Agriculturalists can use their knowledge of an insect’s lifecycle to their advantage by coordinating plantings with theexpected date of hatching. A slight delay in planting of wheat,for example, helps protect it from the destructive Hessianfly. In general, if a pest emerges early in the spring, plantingcan be delayed to avoid that pest (within the limits of thegrowing season). Without food, the pest will perish.

Home gardeners can also foil pests by planting seedlingsinstead of seeds. Certain crops such as lettuce can be moweddown by hungry slugs and other insects when they firstemerge from the ground. If larger seedlings are planted,though, the plant has a better chance of surviving.

KEY CONCEPTSCrops can be planted after the emergence of insect pests sothat the pests have little to eat and subsequently perish.

Planting several different crops on a farm and rotating crops infields from one year to the next are very effective means of re-ducing the growth of insect populations without pesticides.

GO GREEN

Support organizations that pro-mote organic agriculture.

FIGURE 22-9 Strip cropping. Alternating strips of alfalfa with cornon the contour protect this crop field in northeast Iowa from soilerosion and increase productivity of the crops as explained in text.


Altering Plant and Soil Nutrients The levels of certainnutrients in soil and plants can also affect pest popula-tion size. By regulating soil nutrients, then, a farmer maybe able to control pests. Nitrogen is one of the importantnutrients that insects and parasites derive from plants.Too much or too little nitrogen can alter the population sizeof various pests. For example, grain aphids reproduce bet-ter on grains high in nitrogen. Other insects, such as thegreenhouse thrip and mites, do poorly on high-nitrogenspinach and tomatoes, respectively. Once again, knowl-edge reigns supreme. A little knowledge of pest nutrientrequirements, soil nutrient levels, and plant nutrient con-tent can become a useful ally.

KEY CONCEPTS

Controlling Adjacent Crops and Weeds All crops are sur-rounded by forests, meadows, or other crops. Each of thesehouses harmful as well as beneficial insects. To reduce pestdamage, farmers often avoid planting crops that providefood and habitat for harmful pests next to other crops. Thosethat provide habitat for beneficial insects are often encour-aged. Farmers have even used low-value crops to attractpests away from more valuable crops. The former are calledtrap crops. Alfalfa is a good example. When planted adjacentto cotton, it lures the harmful lygus bug away from the cot-ton plants, which prevents serious damage to the cotton.Some farmers may even spray the alfalfa with pesticide to getrid of the bug, using far less chemical than would be neces-sary if the entire cotton crop had to be sprayed.

KEY CONCEPTS

Biological Control: Introducing Predators, Parasites, andDisease Organisms In nature, thousands of potential in-sect pests never become real pests because of natural controlsexerted by predators, diseases, and parasites. If you recall fromyour reading of the ecology chapters, these are biotic com-ponents of natural environmental resistance. Farmers can cap-italize on this knowledge to manage a variety of pestsincluding weeds, insects, and rodents.

To date, scientists have documented well over 300 ex-amples of partial or complete control of crop pests throughnatural predators and parasites. This technique is generallyreferred to as biological control. One classic example of theeffectiveness of biological control is the control of the pricklypear cactus in Australia.

The prickly pear was introduced into Australia from itsnative Mexico. By 1925, over 24 million hectares (60 mil-lion acres) of land had been badly infested. Half of thisland was abandoned because of the thick carpet of cactus.Farmers introduced a cactus-eating moth to Australia

Adjacent weeds or crops may harbor beneficial or harmful insects.Controlling what grows beside a given crop can therefore be a pow-erful tool in protecting crops, with little or no pesticide use.

Insects are sensitive to nutrient levels in plants, so raising orlowering soil nutrients—and thus plant nutrients—can effec-tively control some species. in 1925 to eradicate

the pest, and 7 yearslater, much of the landhad been cleared andcould once again beused (FIGURE 22-10).

The predatorylady beetle was intro-duced into Californiafrom Australia in the1880s to control an insect that destroyed citrus trees. Parasiticinsects from Iran, Iraq, and Pakistan have been introduced tocontrol the olive scale, an insect that once threatened thestate’s olive trees. Both lady beetles and the predatory insectsnow exert complete control on their prey, keeping their pop-ulations at manageable levels without the use of pesticides.

Entomologists in the United States are currently ex-perimenting with a new method of controlling mosquitoesusing Toxorhynchites rutilis (Big Tox, for short), a large, non-biting mosquito whose larvae feed on the larvae of othermosquitoes. Bred in captivity, this predatory mosquito willbe released in infested regions to control biting mosquitoes.

A few insect pests can also be controlled by birds, a nat-ural control organism whose potential has been overlooked.Brown thrashers can eat over 6,000 insects in one day. A swal-low consumes 1,000 leafhoppers in 12 hours, and a pair offlickers can snack on 500 ants and go away hungry. In China,thousands of ducklings are driven through rice fields; insome places they reduce the populations of insects by 60%to 75%, allowing farmers to reduce insecticide use consid-erably. Their droppings also provide fertilizer for the crops.

Bacteria and other microorganisms can be brought tobear on pests. One common example is the bacterium Bacil-lus thuringiensis (bah-SILL-us thur-in-GEEN-siss) or BT, usedto control many leaf-eating caterpillars. Cultivated in the laband sold commercially, it is available as a powder that is ei-ther dusted on plants or mixed with water and then sprayedon plants. Caterpillars that eat the bacteria die because BT pro-duces a toxic protein that paralyzes the digestive system of in-sects. Humans and other organisms are usually unaffected. Iuse BT routinely in my garden to control cabbage butterflies.

FIGURE 22-10Prickly pear cactusinvasion. (a) A pricklypear cactus infestationin Queensland, Aus-tralia. (b) The samearea after the introduc-tion of the cactus-feeding moth.

(a)

(b)


BT is used by organic gardeners with considerable suc-cess. It has been sprayed in China to control pine caterpil-lars and cabbage army worms. In California, it has beenused for more than 20 years to control various crop-eatingcaterpillars, and it is currently applied in the northeasternUnited States to help control gypsy moths, which devas-tate forests. Another strain of BT has been employed in thebattle against mosquitoes in Colorado and other states. Theuse of BT and other techniques has resulted in a measura-ble reduction in insecticide use in certain crops, especiallyalmonds and tomatoes.

Researchers have also successfully inoculated corn plantswith genetically altered bacteria containing the BT gene. Thebacteria multiply in the corn plant as they grow, and they killEuropean corn borers that feed on the stalks. Studies showthat the bacteria do not migrate into the corn kernels.

Viruses and fungi may be used similarly. In Australia, af-ter years of fruitless efforts to control rabbits, scientists in-troduced a pathogenic myxoma (mix-OH-ma) virus, whicheliminated almost all the rabbits within one year. Unfortu-nately, the virus has evolved to an nonvirulent form, andthe rabbit has evolved resistance. Control is no longer as ef-fective as it once was.

Cabbage loopers can be controlled with 0.5 gram of anexperimentally produced virus applied to a hectare of crop-land. Other viruses are being used to control pests such as thepink bollworm, which damages cotton, and the gypsy moth.

Biological control agents must be developed with cau-tion to ensure that they do not pose a threat to humans, live-stock, and natural ecosystems. One of the major concerns hasto do with the introduction of alien species into new envi-ronments, a problem discussed in Chapter 11. Careful test-ing is necessary to be sure that an organism introduced tocontrol a pest does not become a pest itself. In the early1980s in sub-Saharan Africa, for example, an insect knownas the mealybug became a major pest, attacking cassavaplants. This plant produces an edible root that is a staple forabout 200 million people. To find a control for this trouble-some pest, researchers scoured the mealybug’s South Amer-ican homeland for natural enemies. They eventually locateda small parasitic wasp that injects its eggs into the larvae ofthe mealybug. When the eggs hatch, they devour the lar-vae. Before the researchers could release the wasp, though,they had to perform extensive tests to see if the wasp wouldsurvive in its new home and if it would become a pest itself.Convinced that it wouldn’t, the bug was first released in1986 and today is providing protection in 24 African coun-tries. So far, the wasp seems to be working fine.

Another undiscussed problem of biological controls isthat target organisms can develop genetic resistance to them,as did the Australian rabbits mentioned earlier. Researchersin Kansas recently found that larvae of the Indian meal moth,which feed on grain stored in sheds and bins, develop geneticresistance to BT. In such cases new controls could be intro-duced or alternated with BT. In some instances, biologicalcontrol agents themselves may undergo genetic changes thatoffset the newly acquired resistance of the pest. This processis called coevolution. As yet, there is no record of such

changes in biological control agents, but some scientiststhink that they are inevitable.

KEY CONCEPTS

Genetic ControlsIntegrated pest management includes two major geneticcontrol strategies, the sterile male technique and the breed-ing of genetically resistant plants and animals. Both are im-portant components and can be used in conjunction withother methods.

Sterile Male Technique As the previous examples haveshown, a little knowledge of biology can go a long way. An-other example in which knowledge is brought to bear onpest control is the sterile male technique. As the name im-plies, this technique involves the introduction of sterilemales of insect pests into the environment. Males are raisedin captivity and sterilized by irradiation or by exposure to cer-tain chemicals. The sterilized males are then released in largenumbers in infested areas. The males far outnumber the fer-tile wild males and thus account for a large percentage ofthe matings with wild females. Because many insect speciesmate only once, eggs produced by such a union are infertile.Thus, if the population of sterilized males greatly exceeds thatof the wild males, most of the eggs will be infertile. Insect pop-ulations can be brought under control swiftly.

The sterile male technique has been used effectivelyagainst several species of insect pests, including the screw-worm fly in Mexico and the United States, the Mediterraneanfruit fly in Capri, the melon fly on the island of Rota (nearGuam), and the Oriental fruit fly on Guam.

The sterile male technique has not always succeeded. Ithas, for instance, proved unsuccessful in mosquito control.Scientists believe that the chief reason for its failure in thisinstance is the lower sexual activity of sterilized males com-pared with wild males. Other reasons may include an inad-equate number of sterile males, ignorance of the insect pest’sbreeding cycle, the in-migration of additional pests, and im-patience on the part of state agricultural agents. Some re-searchers also suggest that through natural selection a newstrain of insects may evolve that recognizes and avoids ster-ile males.

Despite these problems, the sterile male technique isan important tool in integrated pest management. It is speciesspecific, can be used with environmental controls, and canbe effective in eliminating pests in low-density infestations.

KEY CONCEPTS

Developing Resistant Crops and Animals Many speciesare naturally resistant to pests and disease organisms. How-

Many insects breed only once, so the introduction of large num-bers of artificially sterilized males into a pest-infested region willresult in an abundance of sterile eggs.

Many natural biological control agents can be used to preventthe outbreak of pest species.


ever, crop species often have lost their resistance throughyears of special breeding programs aimed primarily at in-creasing yield. Many geneticists think that introducing genesthat provide genetic resistance to crops can help reduce oreliminate pesticides. For example, researchers have found thatcertain oils in the skins of oranges, grapefruits, and lemonsare highly toxic to the eggs and larvae of the Caribbean fruitfly, which lays its eggs in the skins of these fruits. The flies’larvae destroy the fruit, but scientists may now be able tobreed citrus selectively to increase the amount of toxic oilsin their peels. By creating natural resistance, this techniqueeliminates the need for pesticides.

Cornell University scientists are developing a potatoplant whose leaves, stems, and sprouts are covered with tiny,sticky hairs that trap insects and immobilize their legs andmouth parts. Field tests show that this plant can reduce byhalf the infestation of green peach aphids, which (despite theirname) also attack potatoes. The new variety was developedby crossing cultivated potatoes with a wild species withsticky hairs, which grows as a weed in Bolivia.

Other genetic research has led to Hessian fly-resistantwheat and leafhopper-resistant soybeans, alfalfa, cotton, andpotatoes. Work on chemical factors that attract insects toplants may help scientists selectively remove them to makeplants unappealing.

The Monsanto Company is working on another prom-ising weapon in the fight against pests. Robert Kaufman andhis colleagues have isolated the gene that gives BT its pesti-cidal action. The scientists have transferred that gene to an-other bacterium, Pseudomonas fluorescens, which lives on theroots of corn and several other plants. The transplanted generenders the host bacterium lethal to insects and other or-ganisms, such as the black cutworm, that feed on the rootsof commercially important crop species. Simply by plantingseeds that have been pretreated with P. fluorescens bearingthe toxic gene, farmers may be able to provide long-term pro-tection without many of the dangers of pesticides. However,widespread use of BT in corn and other crops may result inthe development of resistance and loss of the BT control.

Monsanto hopes that more insecticidal genes can beadded to P. fluorescens in the years to come, giving corn awider range of protection, reducing chemical pesticide useand in the process protecting wildlife from the harmful toxicpesticides that have been the mainstay of agriculture fordecades.

Root-zone protection is not the only strategy that ge-neticists are developing. Numerous bacteria colonize above-ground plant parts; fitted with insecticidal genes from BT andother naturally occurring biological agents, these bacteriacould create a protective barrier to ward off dozens of in-sect pests.

KEY CONCEPTSPlants and animals that are resistant to pests and diseases can bedeveloped through genetic engineering and artificial selection.Bacteria that live on the roots and other parts of plants can alsobe genetically engineered to make them lethal to insect pests.

Chemical ControlsChemical controls are also be a part of IPM. These chemicalsare conventional pesticides and a new breed of natural (pre-sumably nontoxic) substances. First, though, we look at theconventional pesticides.

Reducing the Use of Second-Generation Pesticides Evenwith wider use of biological control agents and other strate-gies of IPM, second-generation pesticides will likely remaina part of our pest control strategy for many years to come.However, several principles should guide their use: (1) Theyshould be applied sparingly; (2) they should be applied at themost effective time to reduce the number of applications; (3)they should destroy as few natural predators, nonpest species,and biological control agents as possible; (4) they should notbe applied near drinking water supplies; (5) they should becarefully tested for toxic effects; (6) they should be avoided ifthey are persistent and tend to bioaccumulate; (7) they shouldbe used in ways that reduce exposure to workers and nearbyfamilies; and (8) they should be used to reduce populationsto low levels, with environmental, genetic, and cultural con-trol measures used to maintain populations at low levels.

One way to minimize the use of insecticides is to sprayonly affected areas. Insects, for example, may infest a smallportion of a crop. If possible, only that portion should besprayed. A technique that is useful for herbicides is the useof special wick applicators, rather than sprayers, which de-liver a small dose directly to the target species with minimumenvironmental contamination (FIGURE 22-11).

Timing of application also helps farmers reduce pesti-cide use. Consider an example. The red spider mite can bekept under control in apple orchards by applying insecti-cides early in the season, well before the mite’s natural pred-ators emerge. Throughout the rest of the season, the natural

FIGURE 22-11 Wick applicator. Instead of spraying the entirecrop with herbicide, farmers can use this device to apply pesti-cides only to the weeds growing between the rows.


predators will keep the spider mites under control. No fur-ther pesticides are needed. By using a similar approach oncotton, researchers at Texas A&M have cut pesticide use by70% while maintaining normal cotton crop production.

Better monitoring of crops also help reduce pesticideuse. Some farmers spray their entire crop when they en-counter any pests. They don’t even bother to see how ex-tensive the infestation is. In many cases, only a tiny portionof the crop needs spraying, a discovery that could result inconsiderable savings of time and money.

Others spray on a routine schedule, often provided bythe pesticide salesperson, without even checking to see ifinsect pests are about. Schedules may not reflect the needsof farmers’ crops. Were farmers to check, they might findthat the pests were under control—or weren’t even there. Alittle monitoring might save lots of time, money, and envi-ronmental contamination.

Successful IPM requires a better understanding of insectbiology, as well as better skills in recognizing and countinginsects in a farmer’s fields. By knowing what insects are pres-ent, and where, farmers can become wiser participants inthe ecosystem they manage.

Finally, more developed nations have an important roleto play by discouraging companies from exporting bannedpesticides to less developed countries, where they often re-turn on the produce we import. The rich can also help thepoor develop a sustainable pest management programthrough technical and financial assistance.

KEY CONCEPTS

Third-Generation Pesticides This section discusses awhole new arsenal of chemicals that are produced in natureand could, with a little ingenuity, be applied to pest controlon a large scale. These nontoxic agents, such as naturalchemical repellants, could, in conjunction with measuresoutlined previously, displace potentially harmful second-generation pesticides. This new class of chemical compoundsis sometimes referred to as the third-generation pesticides.

KEY CONCEPTS

Pheromones Insects and other animals release chemicalscalled pheromones (FAIR-eh-moans). Pheromones providea chemical means of communication. One well-known groupof pheromones is the sex attractants, which are emitted byfemale insects to attract males at the time of breeding. Effective in extraordinarily small concentrations, pheromonesdraw males to females. This evolutionary adaptation ensuresa high rate of reproductive success.

Scientists and farmers are exploring a whole new group of nat-urally occurring chemicals to control insect pests. These couldeventually become the cornerstone of pest management in asustainable system of agriculture.

Conventional pesticides will remain in use, but they must bescreened carefully to avoid harmful ones. Those that are used mustbe administered with caution—in amounts and at a time whenthey are most effective, to minimize their environmental impact.This requires better monitoring of crops and infestations.

Some sex attractants are now produced commercially andare available for pest control. Some of these substances areused in pheromone traps that lure males. These traps maycontain a pesticide-laden bait or a sticky substance that im-mobilizes insects (FIGURE 22-12). Pheromone traps of vari-ous sorts have been used to control at least 25 insect speciesand can be used with other IPM methods.

Pheromone traps can also be used to pinpoint the timewhen insect eggs hatch. By knowing precisely when insectsemerge, farmers can time their pesticide applications formaximum effectiveness. This technique helps reduce theamounts of pesticide applied.

Another technique for controlling insects with phe-romones is known as the confusion technique. In thismethod, pheromones are sprayed on crops at breeding time.Unsuspecting males are drawn by the pheromone in all di-rections. Fertile females hardly stand a chance and maynever find a partner. One modification of this technique in-volves the release of wood chips treated with sex attrac-tants. Males are attracted to the wood chips and may attemptto breed with them.

Finally, pheromones can be used to lure beneficial in-sects out of fields. Once they are gone, pesticide sprays can beapplied.

The use of pheromones offers several advantages oversecond-generation pesticides. They are, for example, nontoxicand biodegradable and therefore not expected to have any sig-nificant environmental impacts. They can be used at lowconcentrations. Third, they are highly species-specific. Themajor disadvantage is the high cost of developing them.

KEY CONCEPTSPheromones are natural sex attractants released by insects. Theycan be used to draw insects into traps or can be sprayed onfields to confuse males so they cannot find females with whichto mate. These substances are nontoxic and biodegradable.

FIGURE 22-12 Pheromone trap. This trap contains a sticky sub-stance to immobilize male gypsy moths, which are drawn to it insearch of mates by chemical sex attractants known as pheromones.


Insect Hormones The life cycle of many insects is shown inFIGURE 22-13. As illustrated, adult insects lay eggs, which de-velop into larvae (caterpillar stage). The larvae are voraciouseaters and are often the most troublesome form of pestspecies. Eventually, the caterpillar spins a cocoon in whichit undergoes an amazing change, transforming into a flyingform such as a moth or butterfly—the adult form.

The entire life cycle of insects is regulated by two hor-mones, juvenile hormone and molting hormone. Hormonesare chemical substances that are produced by specific cellsin the body and travel through the bloodstream to dis-tant sites, where they exert some effect. Altering thelevels of juvenile and molting hormones disrupts aninsect’s life cycle, sometimes resulting in death.For example, larvae treated with juvenile hor-mone are prevented from maturing and eventuallydie. If given molting hormone, they will enter thepupal stage too early and die. Interestingly, someplants contain chemicals structurally similar to ju-venile hormone, an evolutionary adaptation thathelps protect them from hungry insects. When in-gested by larvae, these chemicals prevent the larvaefrom pupating. This, in turn, prevents formation ofthe adult form that produces eggs and additionalgenerations of larvae.

Insect hormones applied to crops offer manyof the same advantages that pheromones offer, in-cluding biodegradability, lack of toxicity, and lowpersistence in the environment. Like pheromones,however, they are costly. Insect hormones actrather slowly, sometimes taking a week or two toeliminate a pest, by which time extensive damage may havebeen done. In addition, insect hormones are not as speciesspecific as pheromones and therefore may affect naturalpredators and other nonpest species. The timing of applicationis also critical, for hormones are effective only at certaintimes in an insect’s life cycle.

Researchers recently discovered a plant from Malaysiathat produces juvenile hormone. They hope that the genesresponsible for the production of this hormone can be trans-ferred to commercially important crops, offering anotheravenue of protection.

KEY CONCEPTS

Natural Chemical Pesticides Natives of the South Americantropics have used the seeds and leaves of the neem tree formany years to control pests. Researchers have found thatthis tree produces chemicals that kill or repel a variety ofinsects. This extract may become useful in the control oflarvae that feed on vegetables and ornamental crops.

Egyptian researchers found that flies ignored a speciesof brown algae left out on a counter to dry. Curious, re-

Two hormones control the life cycles of insects and can besprayed on crops to alter these cycles and lead to the death ofpests. Unfortunately, to be effective, application must be pre-cisely timed and these hormones take a fair amount of time tokill off a pest.

searchers extracted a mixture of chemicals from the algae andfound that they, too, repel a variety of insects that attack cot-ton and rice. Natural chemicals such as these may proveuseful in years to come. Like other third-generation pesticides,they are biodegradable and nonpersistent.

Researchers have also found that some plants producechemicals that alter insect metabolism. Petunias, for exam-ple, synthesize a chemical that dramatically stunts the growthof corn earworms. Scientists hope that they can transfer thegenes to crop plants, through either genetic engineering ormore conventional means, to provide a natural protectionagainst pests, thus providing an on-site means of control.Nicotine, caffeine, and citrus oil are all natural insecticidesand are under investigation today.

Gardeners often use insecticidal soap and hot pepper tospray their plants to control insects such as pesty white fliesand aphids. I’ve used them for years on vegetables and or-namentals grown in my indoor planters. Gardeners also usepyrethrums, a naturally occurring substance derived fromplants. It’s an effective pesticide against many insects.

KEY CONCEPTSPlants have evolved many natural insect repellants that can becommercially produced and sprayed on crops to help controlpests.

Mating

Adult stage

Pupa

Pupation

Laying eggs

Eggs

Larvae

Caterpillar

Metamorphosis

FIGURE 22-13The insect life cycle.


Cultural ControlsThe final components of IPM are the cultural controls, anyone of a dozen techniques to control pest populations thatdo not fall under the previous categories—environmental,genetic, and chemical. These methods include cultivation tocontrol weeds, noisemakers to frighten birds, and manual re-moval of insects from crops (especially suitable for garden-ers). Also included in this group are such measures asdestroying insect breeding grounds; improved forecastingof insect emergence; quarantines on imported foods, no-tably fruits and vegetables, to prevent the spread of pests; andwater and fertilizer management to ensure optimum crophealth and resistance to pests. One of the most badly neededcultural controls is monitoring.

KEY CONCEPTS

Educating the World About Alternative StrategiesAccording to a report by Worldwatch Institute’s Peter Weber,“Farmers seem to see in pesticides . . . the illusion of a guar-antee, which they can never get from the weather, markets,or politicians.” Some banks even require farmers to use pes-ticides to qualify for crop loans.

With a little imagination and thought, farmers are find-ing that they can reduce pesticide use by 50% and still notlower harvests. As farmers like Ron Rosmann are finding, theycan even find ways to curtail pest damage without chemicals.

Training the world’s farmers in IPM is vital to efforts tobuild a sustainable society. This will require a massive edu-cational effort. Schools and universities, extension services,and even agricultural magazines can help retrain farmers.

For many years, though, in virtually all countries, farm-ers have received most of their advice on pest control fromthe sales reps of the chemical manufacturers that produce pes-ticides—who have an obvious conflict of interest. In someuniversities, much of the research on pest control is spon-sored by pesticide manufacturers, which may bias the sys-tem. In the United States, for example, the Department ofAgriculture spends under 25% of its $109 billion annualbudget on IPM and sustainable agriculture. In contrast, pes-ticide companies shell out $1.7 billion a year for research anddevelopment of chemical controls.

Fortunately, many farmers have become aware of the pit-falls of the indiscriminate use of pesticides. Cost conscious-ness has led to efforts to seek alternatives on the part of bothsmall farmers and large corporate farms. In addition, severalU.S. universities have sustainable agriculture programs thatteach students about IPM, among other subjects. Students atIowa State University and the University of California at Davis,for example, can learn cost-effective ways of controlling pestswithout chemicals or with minimal use of them. State uni-

Insect pests can be controlled by many techniques that do not re-quire the use of chemicals. These are called cultural controls andinclude measures such as noisemakers to frighten birds from crops,manual removal of insects, and quarantines on imported food.

versity extension programs also provide information to farm-ers and gardeners on alternatives to chemical pesticides.

Universities in the less developed countries are also be-ginning to train farmers and students. Birzeit University onthe West Bank in Palestine, for instance, recently embarkedon a program to help reduce the use of pesticides in Pales-tine and introduce farmers to integrated pest managementthrough an ambitious educational campaign.

In less developed countries, agricultural departmentshave trained farmers in IPM and encouraged them to edu-cate fellow farmers. In Indonesia, the government trained andhired 2,000 crop scouts. These scouts work with farmers tomonitor insect populations and also teach the farmers thetechniques of IPM. Farmers can also work together with-out government support. Ron Rosmann, introduced at thebeginning of the chapter, is a member of Practical Farmersof Iowa (PFI), a group of more than 500 farmers interestednot only in cutting costs but also in preventing soil erosionand using fewer chemicals—ultimately, farming more sus-tainably. Groups like PFI have been started in several otherstates as well. Farmers who belong to such groups are pio-neering new ways to produce crops that could result in dra-matic decreases in the use of pesticides while maintaining orincreasing yields. By sharing their ideas with nonmembers,they can spread the word to a broad range of farmers.

Farmer groups are also beginning to form in less devel-oped countries. Bolivian farmers, for instance, recentlyformed a group called the Association of Ecological Pro-ducers. A similar group was formed in Mexico and draws offa long tradition of pesticide-free agriculture. Mexico’s 13,000organic farmers export an estimated $20 million worth of foodto the United States and Europe.

Nongovernmental organizations or NGOs—amongthem, consumer and environmental groups—can play a ma-jor role in educating farmers and government officials world-wide. A recent ban on several widely used and highly toxicpesticides in the Philippines, for instance, is the result ofthe efforts of numerous NGOs. Concerted efforts on their partresulted in a dramatic shift in official and public opinionaway from using chemical pesticides toward safer alternatives.The success of these groups can be attributed in large partto the efforts of the NGOs to demonstrate alternatives thatare available to farmers. NGOs have also publicized researchshowing that crop yields don’t have to fall when pesticidesare abandoned. Through their work, they have successfullypromoted the idea of IPM, which has gained wider accep-tance than the chemical pesticide dogma promoted by chem-ical companies.

The shift to pesticide-free farming will require attitudechanges on the part of consumers, too. To make sustainableagriculture successful will require buyers to choose organic pro-duce. In some cases, organic produce is competitively priced.In most cases, though, it costs more. So, consumers must bewilling to pay extra to support this growing industry. Many con-sumers will have to rethink and change their buying habits.They will have to learn to accept slightly blemished fruits andvegetables rather than demand picture-perfect produce madepossible only by the heavy application of chemical pesticides.


A few more spots on our oranges could mean many morebirds overhead, cleaner waterways, improved health for work-ers and the general public, and cheaper oranges. They won’tchange the nutritional value of the produce one bit.

KEY CONCEPTS

Government Actions to EncourageSustainable AgricultureGovernments can promote sustainable agriculture by provid-ing low-cost crop insurance for farmers who make the transi-tion to IPM. As a farmer shifts from chemical-intensive use toIPM, losses can be severe because the ecology of the farm maybe severely out of balance. With insurance, farmers can weanthemselves from pesticides and not go bankrupt in the process.

Educating farmers and others about alternative strategies is im-perative if sustainable pest management is to become widelyadopted the world over. Universities, agricultural agencies, farm-ers’ groups, and nonprofit organizations are several of the av-enues available for this important task.

Governments can also help by developing organic cer-tification programs. Developed nationally and in severalstates, such as Colorado and California, these programs setstandards farmers must meet to permit them to label theirproduce “organically grown.” Certification will avoid dishon-esty and help consumers determine which produce is trulypesticide-free. It could also stimulate other farmers to thinkabout switching to chemical-free methods of farming. To thedelight of many people, numerous U.S. farmers have alreadymade the switch. In 1999, the Organic Farming Research Foun-dation estimated that there were 6,600 certified organic grow-ers in the United States. That’s good news to some, but it isonly a small fraction of the 2 million U.S. farmers.

You can help, too by purchasing organic produce and tak-ing other steps suggested in the Go Green sidebars.

Our doubts are traitors and make us lose thegood we oft might win by fearing to attempt.

—William Shakespeare

CRITICAL THINKING

Exercise AnalysisAs with many other issues, it is important to dig deeper and always consider the big picture. It is crucialto uncover biases that may enter into the arguments of some proponents as well. Scrutinize the experi-ment reported in the newspaper. Was it performed correctly, and are the results applicable to humans?

Suppose you found that the results were valid. You would then want to look at the next most impor-tant question: Should the pesticide be banned? In the public policy arena, this question pivots on anotherrelatively simple question: Are the risks worth the benefits?

In order to answer this, it is necessary to seek more information and viewpoints. If you did, you mightfind that farmers and pesticide manufacturers would argue that this insecticide helps them prevent cropdamage, which saves farmers millions of dollars a year. They also say that pesticides make food cheaperfor consumers. The pesticide manufacturing industry also provides thousands of jobs. Farmers provide foodfor billions of people. In the developing world, this food keeps millions of people alive.

As for the costs, if EPA estimates are correct, 10 to 20 U.S. citizens will contract cancer each year, andmany of them will die each year. The pesticide may also contaminate groundwater, kill fish and birds, andhave other adverse environmental effects.

When you dig deeper, you would very likely find that there are alternative ways of controlling insectswithout using potentially harmful pesticides. These methods may have the added benefit of reducinggroundwater contamination and mortality in birds, fish, and other wildlife. In some cases, alternativemethods lower crop yield, but because of lower input costs, farmers make as much or even more money.

Can you think of any other costs and benefits? After analyzing both sides of the argument, what isyour opinion? Should the pesticide be banned? Would your opinion change if you were one of the cancervictims? If you were a farmer?


CRITICAL THINKING AND CONCEPT REVIEW1. List and discuss reasons why pest damage is high in

developed nations despite the extensive use of chemi-cal pesticides.

2. Critically analyze this statement: “Without pesticides,crop damage in the United States and other major foodproducers would be much higher.”

3. Describe some of the environmental and health prob-lems caused by the use of pesticides. How can they beavoided?

4. How are beneficial species affected by insecticide use?Give some examples.

5. What does the term pesticide treadmill refer to?6. Why do DDT and other chlorinated hydrocarbons persist

in the environment? Why do they cause problems eventhough they are found in low concentration in water?

7. Make a list of the major components of integrated pestmanagement. What role do soil conservation measuresdiscussed in Chapter 10 play in pest control? What ad-

vantages does IPM strategy offer over current manage-ment techniques?

8. Explain why crop rotation and increasing crop diversityreduce pest populations.

9. Describe some of the biological control methods. Giveexamples. Using your knowledge of biology and evolu-tion, would you expect pest species to develop resis-tance to biological controls?

10. Describe why the sterile male technique works.11. Discuss some ways in which genetic engineering may

be used to help cut down on pest damage.12. You are appointed director of the state agricultural de-

partment. Outline a way to encourage farmers to mini-mize and ultimately eliminate pesticide use.

13. Using critical thinking, analyze this statement: “U.S.agriculture cannot go organic. We cannot eliminatepesticides without greatly reducing productivity andfarmers’ profits.”

KEY TERMS Agent Orangeauxinsbiological controlbiomagnificationbroad-spectrum pesticidescarbamateschlorinated hydrocarbonscoevolutionconfusion techniquecrop rotationcultural controlsDDT (dichlorodiphenyltrichloroethane)dioxinsenvironmental controlFederal Insecticide, Fungicide, and

Rodenticide Act (FIFRA)

first-generation pesticidesFood Quality Protection Actgenetically resistant insectsherbicidesheteroculturehormonesintegrated pest management (IPM)integrated weed managementjuvenile hormonemolting hormonenarrow-spectrum pesticidesnongovernmental organizations

(NGOs)organic certification programsorganic phosphatesorganic produce

pesticidespesticide treadmillpheromonespheromone trapspyrethroidsregistrationsecond-generation pesticidessex attractantssterile male techniquestrip croppingthird-generation pesticidestolerance levelstrap cropstriazinesupset

Connect to this book's website:http://environment.jbpub.com/9e/The site features eLearning, an online reviewarea that provides quizzes, chapter outlines,and other tools to help you study for yourclass. You can also follow useful links for in-depth information, research the differingviews in the Point/Counterpoints, or keep up on the latest environmental news.

REFERENCES AND FURTHER READINGTo save on paper and allow for updates, additional readingrecommendations and the list of sources for the informationdiscussed in this chapter are available at http://environment.jbpub.com/9e/.

chapter 22 pests and pesticides: growing...

Documents