insecticides · 2017. 6. 5. · warm-blooded animals. chemical sterilants the most successful use...

Insecticides

196

OBJECTIVEToidentifyinsectpests

andselectandapplythe

appropriatesynthetic

(man-made),biological,

orbiorational(derived

fromitemsinnature)

insecticides.

KEY TERMSaerosols

attractants

biological

biorational

insect

insecticides

pheromones

repellents

syntheticpesticides

U N I T

18

COMPETENCIES TO DEVELOPAfterstudyingthisunit,youshouldbeableto:

identifycommoninsectpestsandselectaneffectivecontrol

methodforeach.

describethesevenwaysinwhichinsectsarekilledby

insecticidesandthetypeofinsectagainstwhicheachismost

effective.

listthenamesandcharacteristicsofthethreemajorgroups

ofinsecticides(accordingtotheirchemicalmakeup).

comparethesixwaysinwhichinsecticidesareapplied.

explaintherelationshipbetweenthelifecycleofinsectsand

timingofinsecticideapplication.

Identifythecommonbiologicalcontrolsofinsects.

MATERIALS■ illustrationsofinsectpests

■ liveinsects

■ recommendationsforsprayingfromthelocalextensionservice

■ insecticideswithlabels(noneshouldbehighlytoxic)

■ sprayinganddustingequipment

■ safetygear,includingelbow-lengthprotectiveglovesandrespirator

80392_18_Unit18_p196-206.indd 19680392_18_Unit18_p196-206.indd 196 2/26/10 4:47:50 PM2/26/10 4:47:50 PM

Copyright 2011 Cengage Learning, Inc. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.

197

INSECTICIDES UNIT 18

How Insecticides KillTo be considered good insecticides, chemicals must kill a specific type of insect while doing little or no damage to the plant. They must also be as safe as possible for the handler and environment.

STOMACH POISONS These poisons work against insects that actually eat a part of the plant. The chemical is sprayed or dusted on the plant; as the insect eats the plant, it is poisoned through the stomach. Insects that chew their food, such as caterpillars, grasshoppers, and beetles, are con-trolled by stomach poisons. Rotenone is consid-ered to be an effective stomach poison.

CONTACT POISONS These insecticides kill insects when they are hit by or come in con-tact with the poison; the insect does not have to consume it. Any type of insect can be controlled by contact poisons, including insects that suck plants, such as aphids and leafhoppers. Contact poisons kill by upsetting the insect’s nervous sys-tem or breathing system. An example of a con-tact insecticide is malathion.

New, highly refined oil sprays are excellent contact poisons against insect eggs and soft-bodied insects, such as aphids, mites, scale, and whiteflies. Oils do not contaminate the environ-ment and are safe to use.

SYSTEMIC POISONS These chemicals enter the plant sap and move throughout the entire plant. When insects eat parts of plants or suck juice from plants, the chemical is swallowed. Systemic poisons are effective in the control of insects with either chewing or sucking mouth parts. They are especially effective in controlling insects that hide under leaves or underground and that therefore are not affected by contact sprays. If used on plants that are consumed as food, the chemical must be given time to break down within the plant and become nonpoison-ous before the harvest date for the crop. These poisons are sprayed on the plant foliage or mixed with water and applied to the roots. Both meth-ods result in the chemical spreading through-out the entire plant. One systemic insecticide is Orthene (acephate).

FUMIGANTS Fumigants are actually con-tact poisons applied in gaseous form. The gases or fumes kill the insect after entering its sys-tem through breathing pores. The insect must

INSECTICIDES, one of the seven types of pesticides

mentioned in the previous unit, are used by most peo-

ple at one time or another in the control of flies, mos-

quitoes, and other insect pests. They are used widely by

horticulturists to protect plants from insect damage.

Although insecticides can effectively and safely con-

trol insects, they can be dangerous and even deadly to

human beings when used improperly. For this reason,

it is extremely important that they be handled with

care and only according to directions on the label.

This unit deals with chemical insecticides, not the biological insecticides discussed in Unit 16. Because changes in available insecti-cides are occurring rapidly, a list of suggested insecticides is no longer included in this unit.

What Is an Insect?An insect is a small animal with three clearly defined body regions and three pairs of legs. The three body regions are the head, thorax, and abdomen (Figure 18–1). The proper identi-fication of insects is an important step in their control. Only after the insect is identified can the best method of control be selected. Guides to insect identification are available from the U.S. Department of Agriculture.

HEAD

LEGS THORAX

ABDOMEN

FIGURE 18–1 Parts of an insect. Notice that there are three definite body regions (head, thorax, and abdomen), with the legs attached to the thorax.

Delm

ar/

Cengage L

earn

ing



198

SECTION 5 INTEGRATED PEST MANAGEMENT

The Chemical Makeup of InsecticidesInsecticides are classified in three major groups according to their chemical makeup.

Inorganic CompoundsInorganic compounds are of mineral origin. That is, a mineral is used as the basis for the poison. They usually work in the form of stomach poi-sons. Sulfur is one type of inorganic insecticide and is also widely used as a fungicide.

Organic CompoundsOrganic compounds are those derived from plants. They usually work in the form of stom-ach poisons or contact poisons. Two examples of organic compound poisons are rotenone and pyrethrum, which are very safe when used according to the directions on the label.

Synthetic Organic CompoundsThese chemicals are of relatively recent origin, many of them having come into use in the last 30 to 35 years. They are very effective against insects, but many of them are also toxic to human beings. Synthetic compounds are insect controls that are man-made pesticides. The synthetic insecticides tend to have a harmful effect on beneficial insects. This large group of insecticides is subdivided into three smaller groups: chlorinated hydrocarbons, organophosphates, and carbamates. They are not found naturally as are the organic compounds listed above but are produced in the laboratory.

CHLORINATED HYDROCARBONS These insecticides contain chemicals that have long residual control; that is, they continue to kill long after the initial application. DDT is one of the best-known chemicals in this group. It is no longer sold in the United States, however, because of concern about the buildup of the poi-son in the environment and the bodies of warm-blooded animals. Chemicals from this group are being phased out.

ORGANOPHOSPATES This group of insect icides is very effective in controlling insects. It also contains some of the chemicals most toxic

actually absorb the poison for this insecticide to be effective. Fumigants are used to control soil-borne insects that damage roots, such as weevils and June beetle grubs. One example of a fumigant is methyl bromide. In the United States most uses of methyl bromide were phased out on January 1, 2005.

Fumigants are also used in greenhouses. When applied in the greenhouse, the fumigant, consisting of tiny particles of insecticide, settles on the insect and is breathed into its system.

REPELLENTS Repellents generally do not kill insects but, instead, drive them away before they attack the plant. One example of a repellent is aluminum foil, which, when placed around plants, repels flying insects (Figure 18–2).

ATTRACTANTS AND PHEROMONES Attractants and pheromones work in the oppo-site way from repellents; they lure insects to their deaths. One example is the Japanese beetle bait used in traps to catch the beetle. Another exam-ple is the sex lure used to trap the gypsy moth. The sex lure used in these traps is made from naturally occurring or synthetically produced hormones that attract the adult insects. The male gypsy moth is irresistibly attracted to the sex lure; this attraction is stronger than the normal attraction he has to the female moth. Since most of the male moths are caught in the trap, the females remain unfertilized and lay sterile, unfertilized eggs that do not hatch. The sex lure acts in the same man-ner on the Japanese beetle.

FIGURE 18–2 Aluminum foil strips around cucumber plants protect the plants from flying aphids by reflecting ultraviolet rays from the sky, making the area undesirable to the aphids.

De

lma

r/C

en

ga

ge

Le

arn

ing



199


Application of InsecticidesDustsInsecticides are applied with dusters if purchased as dusts. The chemical is already diluted when bought; it requires no mixing before application.

Dusts are easy to apply with inexpensive equipment but tend to blow or drift from the tar-get (Figure 18–3). This drifting can damage other crops or contaminate the environment.

Wettable PowdersWettable powders (WPs) resemble dusts in appearance but are concentrated and must be diluted with water before application. Read the directions for the amount of insecticide to mix per gallon of water. Wettable powders tend to settle while in solution and must be stirred while being sprayed. Some powders are pressed into granules that release less dust into the air dur-ing mixing.

With a water-mixed spray, better coverage of plants is usually possible and less drift occurs (Figure 18–4).

Emulsifiable ConcentratesEmulsifiable concentrates (ECs) are liquids that are mixed with water in the same manner as wet-table powders. The concentrate is safer to han-dle because there is no powder or dust to blow during mixing. Emulsifiable concentrates do not

to warm-blooded animals. Parathion is so toxic that 1 drop of the concentrated chemical in the eye can kill a human being. These chemicals are also absorbed rapidly through the skin. Mala-thion, another chemical in this group, is a rela-tively safe chemical, and one that can be used to control many insects.

C a u t i o nReadtheinsecticidelabelforcautioninuseof

thesechemicals.

Organophosphates break down quickly in the environment (within 15 to 30 days) and do not build up in the bodies of warm-blooded ani-mals. This group may also soon be phased out.

CARBAMATES This group of synthetic organics contains some of the safest insecticides on the market. Carbamates such as carbaryl (Sevin) are very effective in killing some insects although not effective in killing others. They are slightly toxic to warm-blooded animals. Carbam-ates break down rapidly (in 2 to 7 days) and leave no residue to contaminate the environment. These chemicals do not build up in the bodies of warm-blooded animals.

Chemical SterilantsThe most successful use of sterilants involves gamma radiation treatments to sterilize insects so they cannot produce offspring. One method is to sterilize male insects and release them to mate with females. Because the eggs are not fer-tilized, they will not hatch when deposited by the female. This is a very effective method in the con-trol of certain insects such as the screw worm, which infests cattle. This process is also being tested for use on plant insect pests such as the gypsy moth.

As insects become resistant to existing chemical pesticides, new types of controls are developed. These new chemicals are totally different in their action on insects and are more effective for now and into the future. It is expected that insects will eventually become resistant to these also, and the search for more biological controls will continue. Biological controls seem to be more effective over a longer period of time.

FIGURE 18–3 Nontoxic dust being applied. Note how the dust drifts away from the target plants.

Delm

ar/

Ceng

age L

earn

ing



200


AerosolsAerosol insecticides are contained in pressurized cans. They are generally used for small insect con-trol jobs around the house or in the greenhouse. The chemical is already diluted and ready for use when purchased (Figure 18–5). Many aerosols in the form of bombs are available for use in the greenhouse. The bombs are punctured and the chemical is slowly released as a fine mist.

SpikesSpikes of various sizes and shapes containing sys-temic pesticides are available. Small spikes are pushed into the soil in pots and larger ones driven in around the plants in the landscape. Plant roots pick up the chemical, and it spreads throughout the plant. The pesticide is released over a long period of time, giving extended protection.

EquipmentHand-Operated Dusters and SprayersApplication of insecticides on school grounds or in greenhouses can be done safely using inex-pensive hand-operated sprayers and dusters. An explanation of the safe use of each of these pieces of equipment will be given by the instructor.

settle and separate from the solution, as wetta-ble powders do, and give the same good coverage of plants. Shelf life of these chemicals is generally longer than that of dusts or wettable powders if the container is kept closed and stored in a cool, dark place.

GranulesGranules are insecticides in the form of small pellets. They are spread on the soil surface where they either penetrate the soil after the applica-tion of water or turn into gases that fumigate the insects. Some of the systemic insecticides mentioned in this unit are sold in the form of granules. They may be applied to the soil in granulated form and watered in, after which the chemical is absorbed by the roots of the plants. One of the newest systemic insecticides avail-able in granular form is imidacloprid, sold under the trade names Merit, Marathon, and others.

BaitsBaits are poisonous materials that attract insects. The pest eats the bait and is killed by the poison. Slugs, snails, cutworms, grasshoppers, and wee-vils are examples of pests that are controlled in this manner.

FIGURE 18–4 Sprayer being used to spray potatoes. There is very little drift with spray, a water solution.

FIGURE 18–5 Sprays commonly used by the homeowner. The can on the left is an aerosol. The others use manual power to spray or dispense the chemical.

De

lma

r/C

en

ga

ge

Le

arn

ing

De

lma

r/C

en

ga

ge

Le

arn

ing



201


Applying the Proper AmountWhatever method of application is used, it is important that the proper amount of the chemical is applied to a given area. This requires calibra-tion of sprayers and dusters. Calibration involves measuring the amount of chemical applied dur-ing a specified period of time or over a measured area and then adjusting the applicator or speed of application to obtain the proper amount of chemical required.

Dusts and sprays must be applied so that there is total coverage of all leaf surfaces. When dusts are applied to plants, they can be seen settling on the surface of the plants, thereby making it easy to see the extent of the coverage. When sprays are used, leaves of the treated plants should be wet just to the point of dripping.

Larger Dusters, Sprayers, and Granular ApplicationLarge-scale commercial application of sprays, dusts, or granules is accomplished by the use of airplanes, helicopters, tractor sprayers, or trucks with special granular spreaders or sprayers. Figure 18–6 illustrates the use of a large boom orchard sprayer.

Airplanes and helicopters are used to spray and dust large acreage of crops, and crops that cannot be treated by ground-operated equipment (Figure 18–7). Commercial applicators apply the specified chemical and charge the grower at a cost per acre. This is an economical way to apply insec-ticides when large areas must be covered quickly.

FIGURE 18–6 A large commercial sprayer applying pesticide to field-grown rhododendrons.

Court

esy o

f C

hesapeake N

urs

ery

FIGURE 18–7 Airplanes are used to apply pesticides on a large scale. Many acres can be covered rapidly by this method.

Court

esy o

f U

.S. D

epart

ment of A

griculture

G R E E N T I PSafe,efficientcontrolofinsectsrequiresthat

theproperconcentrationofthechemicalbe

mixedinsprays.Readthelabelforpropermix-

inginstructions.

Identifying Insect Damage to PlantsTo identify the insect causing damage to plants, the damage itself must be examined. Chewing insects actually eat away part of the plant. This results in holes in the leaves or missing pieces of bark. Chewing insects are controlled by a stomach poison or a contact spray (Figure 18–8).

Sucking insects suck the juices from the leaves of plants. The injury caused by sucking insects is not as easily detected as that caused by chewing insects. Some signals of damage by sucking insects include twisted plant tips and rolled leaves. Plants that are infested by sucking insects may show no signs of infesta-tion at all, but simply appear to be less healthy. Figure 18–9 shows damage to a plant by a suck-ing insect, the aphid. Sucking insects must be controlled with a contact chemical, a fumigant, or a systemic.



202


in before spraying. This is done by examining the insect on the plant.

Insects go through one of the following basic life cycles. The stages during which the insects are controlled are boxed.

❉ Complete metamorphosis:

egg — larva — pupa — adult

❉ Incomplete metamorphosis:

egg — nymph — adult

If the entire insect population of a plant is in an inactive stage, insecticides, other than oil, must not be applied until the eggs hatch or the pupa emerges as an adult. If insects in both active and inactive stages are present, an immediate application of insecticide should be made, with a second application made in 7 to 10 days when the eggs have hatched and before the insect has a chance to mature and lay more eggs. Figure 18–10 illustrates the life cycle of the Japanese beetle.

The integrated pest management system relies on exact timing and less use of chemicals to control pests.

Plants as Insect RepellentsAccording to organic gardening experts, certain plants may be used to prevent attacks by insects on other plants. Figure 18–11 lists some of those plants, along with the insects they repel.

Timing in Insect ControlInsects must be killed when they are actively feed-ing or moving about on the plant. When in the resting (pupa stage) or egg stage, very few chemi-cals can affect insects; however, the new spray oils give control in the egg stage. It is important to determine what stage of growth the insect is

FIGURE 18–8 Damage to leaves by Japanese beetles. These chewing insects are actually eating parts of the leaves. Notice that the tough leaf veins are left uneaten.

Co

urt

esy o

f U

.S.

De

pa

rtm

en

t o

f A

gricu

ltu

re

FIGURE 18–9 Aphids attacking a plant. These insects suck juices from the plant, thereby greatly reducing plant vigor and yield. Notice the ants also present. Ants tend aphids like farmers tend cows. They collect honeydew (a sweet liquid) from the aphids as food and protect the aphids.

Delm

ar/

Cengage L

earn

ing

G R E E N T I PThegreenindustryisusingmorenatural

materialsandinsectpredatorstocleanupthe

environmentandmakeourfoodsupplysafer.

The Organic GardenerAccording to Webster’s Dictionary, organic is defined as relating to, produced with, or based on the use of fertilizer of plant or animal origin without employment of chemically formulated fertilizers or pesticides. These gardens rely on insect repellents that do not include chemicals



203


other plant growth stimulants. This leads to the production of healthier, faster-growing plants that are better able to resist attack by insects and disease.

The natural controls of insects can be accom-plished by using biological, biorational controlsthat are derived from resources of nature. Bio-logical controls are living things that can attack the pests. Some examples of biological controls are milky spore, nematodes, and Bactius the-moginus (Bt).

Biorational controls are non-living materi-als that are not man-made, synthetic material chemical pesticides. Biorationals can impact pests in different ways. They can: give the plant a bad taste that deters pests from feeding on the plant; disrupt the insect’s enstar stage of the life cycle; or by having the pest ingest the product to outright kill the pests. Some examples of biora-tional controls to use are neem oil (oil extract) pyrethrin (extract from chrysanthemums), and insecticidal soap (derived from fatty acids). Bio-products are environmentally friendly, do not last as long, and break down into the ecosys-tem. They are more expensive than synthetic

pesticides and more challenging to incorporate into conventional systems.

in any form—natural enemies, plants, extracts of ground insects used as sprays, natural insec-ticides, crop rotation, sanitation, and resistant varieties.

It is generally accepted that the incorpo-ration of organic matter into the soil and the use of mulches result in better plant growth. This is due to better moisture retention in the soil, more microorganisms that inhibit or kill disease-producing organisms, and increased availability of minor plant food elements and

FIGURE 18–10 The adult Japanese beetle is killed with an insecticide applied as a spray only during June, July, August, and September. The rest of its life cycle is spent underground where it does a great deal of damage to grass roots. Insecticides, in the form of soil chemicals, or the introduction of natural enemies, such as “milky spore,” are used during the larval stage, which is October or in early spring.

Ad

ap

ted

fro

m U

.S.

De

pa

rtm

en

t o

f A

gricu

ltu

re

PLANT REPELS

mint flea beetles, cabbage butterflies

onions, garlic,* aphidschives, leeks

marigolds root nematodes

nasturtiums aphids, cucumber beetles

sage carrot flies, cabbage pests

horseradish potato bugs, other flying insects

*Garlic also inhibits the growth of asparagus.

FIGURE 18–11 Plants reputed to repel insects.

Delm

ar/

Cengage L

earn

ing



204


SummaryInsecticides are gradually making a change from man-made chemicals to natural materials and insect

predators. Many of these natural materials are as effective or more effective than existing chemicals.

Some new man-made materials are copies of materials found in soil fungus and bacteria and plants, and

others are insects. We are cleaning up the environment and making our food supply safer. Many insecti-

cides found on the market a few years ago are no longer approved for use.

Student Activities

1. Observe insect damage to plants. Identify the insect involved and select the proper pesticide for effective control.

2. With guidance from your instructor, demonstrate the proper mixing and application procedures for an insecticide for a live pest discussed in this unit and evaluate the results.

3. Use each piece of equipment described in this unit to properly apply an insecticide. The instructor will demonstrate the proper filling and spraying technique.

4. Visit a local greenhouse operation to observe insect control techniques.

5. Search the Internet using the following terms: insect control; entomology.

6. Explore the Internet web site: <http://www.pest.usda.entomology>.

Self-Evaluation

SHORT ANSWER

Provide a brief answer for each of the following.

1. Detail six ways in which insecticides work to control insects. Include one insecticide in each category and one insect it controls.

2. List the three major groups or families of insecticides and one chemical belonging to each.

Multiple ChoiceSelect the best answer from the choices offered to complete the statement or answer the question.

1. Stomach poison insecticides work besta) on sucking insects. c) on chewing insects.b) as a contact insecticide. d) on nematodes.

2. An example of an inorganic insecticide isa) sulfur. c) malathion.b) Sevin. d) rotenone.



205


3. An example of a natural organic insecticide isa) parathion. c) malathion.b) Sevin. d) rotenone.

4. An example of a synthetic organic insecticide isa) gamma radiation. c) malathion.b) diazinon. d) rotenone.

5. Systemic insecticides are most effective in killing insects that feed bya) sucking. c) night.b) chewing. d) none of the above

6. An example of an insecticide that is used as a fumigant isa) malathion. c) DDT.b) Sevin. d) methyl bromide.

7. Insecticides that remain active in the environment for the longest period of time area) organophosphates. c) chlorinated hydrocarbons.b) carbaryls. d) none of the above

8. The insecticides that are most toxic to human beings are thea) carbamates. c) carbaryls.b) chlorinated hydrocarbons. d) organophosphates.

9. Application of dust insecticides requiresa) a duster. c) a quiet day to reduce drift of the insecticide.b) no dilution. d) all of the above

10. Wettable powders (WPs) are powdered insecticides thata) must be diluted with water.b) are ready to apply with a duster when purchased.c) are used only on chewing insects.d) all of the above

11. Insecticides that come in the form of small pellets and are scattered on the soil surface are calleda) pellets. c) granules.b) baits. d) none of the above

12. Emulsifiable concentrates (ECs) are liquid insecticides that must bea) diluted with water. c) used for chewing insects only.b) used as contract sprays. d) all of the above

13. An insecticide packaged in a pressurized can is called a(n)a) homeowner’s spray. c) home and garden spray.b) convenience package. d) aerosol.

14. The proper amount of spray insecticide has been applied to a plant whena) the bugs begin to die. c) the liquid just begins to drip from the leaves.b) the leaves are damp. d) none of the above

15. When buying an insecticide to eliminate a specific insect, one should purchase a chemicala) that is recommended for that insect. c) that is safe to use.b) only after reading the label. d) all of the above

16. How many pairs of legs do insects have?a) six c) twob) three d) four



206


17. The legs of every insect are fastened to the body part known as thea) thorax. c) abdomen.b) head. d) shank.

18. Synthetic compounds are insect controls that area) man-made pesticides. c) harmful only to spidersb) harmless to beneficial insects. d) none of the above

19. Natural controls of insects can be accomplished by usinga) biological controls. c) mechanical controls.b) biorational controls. d) all of the above

20. Biological controls are living things that can attack the pests. One example of a biological control is:a) Merit. c) Roundup.b) Bactius themoginus (Bt). d) Orthene.

21. Biorational controls area) non-living materials. c) Bad-tasting to the pest so it will not eat the plant.b) not man-made synthetics. d) all of the above



insecticides · 2017. 6. 5. · warm-blooded animals. chemical sterilants the most successful use...

Documents