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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