Pesticides and Pest Control

Dr. Richard ClementsChattanooga State Technical Community College

Key Concepts

Types and characteristics of pesticides

Pros and cons of using pesticides

Pesticide regulation in the US

Alternatives to chemical pesticides

Pests

Compete with humans for foodInvade lawns and gardensDestroy wood in housesSpread diseaseAre a nuisanceMay be controlled by natural enemies

Pesticides: Chemicals that kill undesirable organisms

Insecticides - insect killers Herbicides - kill plants Fungicides - kills fungusNematocides - kill nematodes

(roundworms) Rodenticides - kill rodents

TYPES:

Table 23-1Page 520Table 23-1 Major Types of Pesticides

Type

Insecticides

Chlorinatedhydrocarbons

Organophosphates

Carbamates

Botanicals

Microbotanicals

Examples

DDT, aldrin, dieldrin, toxaphene, lindane, chlordane, methoxychlor, mirex

Malathion, parathion, diazinon, TEPP, DDVP,mevinphos

Aldicarb, carbaryl (Sevin), propoxur,maneb, zineb

Rotenone, pyrethrum, and camphorextracted from plants, synthetic pyrethroids (variations of pyrethrum), rotenoids (variations of rotenone), and neonicotinoids(variations of nicotine)

Various bacteria, fungi, protozoa

Persistence

High (2–15 years)

Low to moderate (1–2 weeks), but some can last several years

Low (days to weeks)

Low (days to weeks)

Low (days to weeks)

Biologically Magnified?

Yes

No

No

No

No

Table 23-1Page 520Table 23-1 Major Types of Pesticides

Type

Herbicides

Contact chemicals

Systemic chemicals

Soil sterilants

Fungicides

Various chemicals

Fumigants

Various chemicals

Examples

Atrazine, simazine, paraquat

2,4-D, 2,4,5-T, Silvex, diuron,daminozide (Alar), alachlor (Lasso),glyphosate (Roundup)

Tribulan, diphenamid, dalapon, butylate

Captan, pentachlorophenol, zeneb, methyl bromide, carbon bisulfide

Carbon tetrachloride, ethylene dibromide, methyl bromide

Persistence

Low (days to weeks)

Mostly low(days to weeks)

Low (days)

Most low (days)

Mostly high

Biologically Magnified?

No

No

No

No

Yes (for most)

First Generation Pesticides

Primarily natural substances Sulfur, lead, arsenic, mercury - used until 1920’s, but still persist in soil.

Plant extracts: nicotine (from tobacco) pyrethrum (from crysanthemums), rotenone (from roots of tropical plants). All are degradable and are plants natural defense against insects.

Second Generation Pesticides -Began in 1939 with DDT

Primarily synthetic organic compounds Broad-spectrum agents - toxic to many species

Target species - intended target Nontarget species

Pesticide Use• 75% are used in developed countries, but use in

developing countries is increasing• 25% of pesticide use in the US is for non agricultural uses: homes, lawns, gardens• Average homeowner applies 10x more per

hectare that US cropland• Imported cut flowers are heavily dosed with

insecticides. • Since 1987 EPA labeled 100 chemicals “known

or potential toxicological concern”

The Case for Pesticides Save human lives

Increase supplies and lower cost of food

Work better and faster than alternatives

Health risks may be insignificant compared to benefits

Newer pesticides are becoming safer

New pesticides are used at lower rates

Characteristics of an Ideal Pesticide

Kill only target pests

Harm no other species

Break down quickly (low persistence)

Not cause genetic resistance

Be more cost-effective than doing nothing

Water0.000002 ppm

Phytoplankton0.0025 ppm

Zooplankton0.123 ppm

Rainbow smelt1.04 ppm

Lake trout4.83 ppm

Herring gull124 ppm

Herring gull eggs124 ppm

Biologicalmagnification

The Case Against Pesticides Genetic resistance

Can kill nontarget and natural control species. More a problem in diverse ecosystems where

predator species are more likely to be able to control pest populations.

Can cause an increase in other pest species

The pesticide treadmill

The Case Against Pesticides

Pesticides do not stay put

Can harm wildlife

Potential human health threats – linked to:Childhood brain cancerImmune, nervous & endocrine system disorders

What can we do?

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA, 1947 & ‘72)

1. requires EPA approval for use by testing on animals

2. EPA sets tolerance levels - amount ofpesticide residue that can legally remain on the crop when consumed.

FIFRA cont’

3. EPA banned chemicals: Most chlorinated hydrocarbons, several carbamates and organophosphates, herbicideSilvex.

4. requires EPA to reevaluate all approved active ingredients.

1993 study of pesticide safety by U.S. Academy of Sciences:

Urged the government to:• Collect better data on pesticide exposure• Develop better tests to evaluate toxicity• Consider cumulative exposure of all

pesticides rather that basing regulation on exposure to single pesticides

Problems with FIFRA

1. Inadequately tested pesticides remain on the market for many years2. Does not allow citizens to sue EPA3. Allows EPA to lisence new chemicals w/o full health and safety data.

How can we strengthen FIFRA?1. Consider cumulative exposure to many pesticides, especially w/ children2. Develop better test procedures

Food Quality Protection Act (FQPA) - 1996

• Requires consideration of exposure to more than one pesticide in foods

• Protects infants and children with tolerance levels 10x smaller

• Requires manufacturers to demonstrate safety of pesticide to children

Food Quality Protection Act (FQPA)

• How to strengthen:• Help prevent contamination of • groundwater by pesticides• Improve safety for farmworkers• Allow citizens to sue EPA

Primary goal of pest control

Economic threshold - pt at which economic losses caused by pest damage outweigh the cost of applying a pesticide.

Why do farmers not use this idea? 1. Careful monitoring of crops is difficult2. “insurance spraying” (apply more just in case)3. Cosmetic spraying - to make things look pretty

Goal should NOT be complete eradication

Integrated Pest Management (IPM)

1. Frequent inspection of crops.2. Crop & it’s pests evaluated in an Ecological

system approach. 2. First use biological and ecological methods. Ex: Crop rotation, pest resistant crops, predatory insects.

3. Chemical pesticides only used when economic threshold reached.

Goal - Reduce pest populations to manageable levels, not eradication.

How can IPM be promoted?•Federally supported demonstration

projects •Sales tax on pesticides to fund IPM

research and education• train USDA field personnel and

county farm agents to help local farmers•Provide subsidies for farmers who use IPM

Effects of IPM

Other Ways to Control Pests Adjusting cultivation practices: crop rotation, adjust planting times, plant trap crops and habitat for predators.

Use genetically-resistant plants: ex: Bt corn. Some disagree as to health and environmental safety.

Biological pest control - ex: predator species, Bt spray, parasites.

Other Ways to Control Pests Use genetically-resistant plants

Biological pest control

Insect birth control

Hormones and pheromones

Ionizing radiation

Advantages of Biological control:

1. Minimizes genetic resistance2. Focuses on target species3. Nontoxic to non-target species4. Saves $ (25$ for each 1$ invested)

Figure 23-7Page 528

Lady bugs(Coccinellidae)

Green lace(Chrysopidae)

Ways to reduce the threat of pesticides in the foods you eat:

•Buy less imported foods•Scrub fruits and vegetables in soapy

water•Buy organic •Grow your own organically