Food & AgricultureChapter 15, Section 2: Pest ControlStandards: SEV4a, b, c

What is a “pest”?• Any organism that occurs

where it is not wanted or that occurs in large enough numbers to cause economic damage.

• Worldwide pests destroy about 33% of the world’s potential food harvest.

• Ex:▫ Fungi (ergot kills corn)▫ Plant eating insects

(grasshoppers)▫ Weeds

Why are wild plants better adapted to avoid pests?• Wild plants are more

spread out than crops which are grown in large fields- harder for pest to find them.

• Wild plants have more pest predators on them that will eat the pest before it gets out of control.

• Wild plants have evolved poisonous chemicals to repel pests.

When plants are attacked by insect, they release a signal that goes to other leaves. These leaves start producing a toxin to protect them when the insect makes its way there.

What are pesticides?• Chemicals that kill insects,

weeds, and other crop pests.• Most are synthetic and some

are petroleum based• Ex: Atrizine-

▫ Herbicide used to kill weeds

▫ Overuse has been linked to hermaphroditism in frogs

▫ Banned in Europe, still used in US

• Ex: Furadan▫ Insecticide▫ Linked to intentional

poisoning of lions in Africa

VIDEO: Lions Poisoned in Kenya

What are the negative aspects of using pesticides?• Insects are developing

resistance due to improper use and overuse of pesticides

• People who live near areas where pesticides are applied have higher cancer rates and nerve disorders (see next slide)

• May affect non-target species (ex: Furadan & lions)

• Many are persistent so they do not break down in the environment. ▫ Can accumulate in soil &

water▫ Ex: DDT (see following

slides)

Pesticides & Child Development• In the picture to the right

children were asked to draw pictures of a person.

• The children from the foothills were not exposed to pesticide spraying. The children in the valley were exposed to pesticide spraying.

• Children exposed to pesticide have delayed development and mental/nerve disorders.

DDT- A Case Study• DDT was used widely as a pesticide in the

1950’s.• In 1970’s it was banned in the US because it

was linked to problems in predatory birds▫ DDT was washing into waterways via rain

runoff.▫ DDT was accumulating in the fat tissue of

small fish.▫ These small fish eaten by big fish.▫ Big fish eaten by eagles, osprey, condors,

etc.▫ Birds getting DDT toxin.▫ DDT made eggshells weak so when birds sit

on them they would break.▫ Bird population declined.

• US still makes DDT but we sell it to developing countries like Africa who use it to control mosquito populations to prevent the spread of malaria.

• Because DDT is persistent you can still detect it in the environment and in human breast milk!

What are some alternatives to using chemical pesticides?

• Biological Pest Control▫ Use of living organisms to control

pests▫ Pathogen- use of a disease

causing organism to kill pests Ex: Bacillus thuringiensis (Bt)

can kill caterpillars when ingested

▫ Plant Defenses- specifically bred to have certain defenses like tougher skin or chemical compounds to repel pests

▫ Chemicals from Plants- using chemicals made naturally by plants as insecticide. Biodegradable Ex: Chrysanthemums secrete

chemical used as commercial insecticide.

What are some alternatives to using chemical pesticides?

• Disrupting Insect Breeding▫ Growth Regulators

Chemical that interferes with some stage of the pest’s life cycle

Ex: Flea prevention pills enter blood stream of dog and when flea sucks dogs blood the growth regulator keeps flea eggs from developing.

▫ Pheromones Hormones released by one organism

to communicate with another. Farmers can release excessive

hormone into fields to confuse males so they can’t find females.

▫ Physical Barriers Male insects may be treated with X-

rays to make them sterile and then released. When mate with females they can’t produce fertilized eggs.

What is Integrated Pest Management (IPM)?• Traditional farming

methods apply a broad spectrum pesticide that kills any and all insect pests.▫ Con: These may kill good

insects too• Modern farming methods

include use of IPM▫ Using a mixture of farming

methods, chemical pesticides, & biological control to reduce pest damage to an economically sustainable level

How does IPM work?• Fields are monitored for pest

activity.• When activity is detected the

appropriate pest control is applied.▫ Biological controls are used

1st- introduce natural predator or pathogen

▫ Cultivation controls are used next- vacuuming or pulling insects off plants can be effective (pulling weeds)

▫ Chemical control- last resort is to add chemical pesticides. Must vary the pesticide so insect does not become resistant

What is selective breeding?• Choosing your plants or

animals that have some desirable trait and breeding them to get a pure genetic line of that trait so offspring have that trait.▫ Ex: Save seeds of corn

cob that has the most kernels of corn. Grow this corn and use pollen of one to pollinate seeds of another so offspring produce LOTS of kernels per corn cob.

Teosinte is where modern corn originated from. Farmers selectively bred it to have more kernels.

What is genetic engineering?• Faster way to produce plants or

animals that have desirable traits.

• Process:▫ Isolate genes form one

organism & implant them into another.

▫ These organisms are called genetically modified (GM)

▫ Ex: Bacillus thuringiensis (Bt)

bacteria has a gene that kills caterpillars.

This gene can be isolated from Bt and inserted into corn

If caterpillars eat corn they die

What are the benefits & risks of GM foods? (See article page 436-437)• Benefits:

▫ Probably more safe than crossbreeding b/c can isolate specific gene you want

▫ Vegetables & fruit can last longer on shelves

▫ Can add nutrients to food (Golden Rice)

▫ Crops can grow close together on small parcels of land- get higher yield

▫ Make food resistant to viruses, fungi, bacteria

▫ Grow faster▫ Have higher yields▫ Can grow in sandy or salty

soil

• Risks:▫ Is it safe to put an animal gene into a

plant gene?▫ Allergic reactions

Arctic fish genes that resist freezing are being added to strawberries so strawberries will be resistant to frost.

What if someone who eats this strawberry is allergic to fish?

▫ Religious or ethical reasons What if you put a pork gene into a

crop and that violates their religious or ethical (vegetarian) beliefs?

▫ Wild plant contamination If you add herbicide resistance gene

to crop and a weed cross breeds naturally and gets that gene then weeds will become resistant and apply herbicide will not kill them

Are you eating genetically modified food?• You probably eat GM

foods everyday.▫ Kool Aid▫ Coke products▫ Anything made with corn,

corn syrup, or soybean Tostitos Doritos

• These foods do not have to be labeled as genetically modified.

What is sustainable agriculture?• Low-input farming• Conserves natural

resources & keeps land productive indefinitely

• Minimizes use of water, pesticide, fertilizer

• Ex:▫ Using crop rotation▫ Growing crops that like

sun to shade others that need less sun

You should be able to…

•Define the term pest•Compare the benefits and environmental

impact of pesticide use•Describe how biological pest control is

part of integrated pest management•Describe how genetic engineering is used

in agriculture.