Chapter 20 Pesticides and Pest Control G. Tyler Miller’s Living in the Environment 13th Edition

Pests Compete with humans for food Invade lawns and gardens Destroy wood in houses Spread disease Are a nuisance May be controlled by natural enemies

Pesticides: Types Chemicals that kill undesirable organisms Insecticides (insects) Herbicides (weeds) Fungicides (fungus) Rodenticides (rats and mice) See Table 20-1 p. 514

First Generation Pesticides Primarily natural substances Sulfur, lead, arsenic, mercury Plant extracts: nicotine (tobacco), pyrethrum (chrysanthemum), rotenone (tropical legumes) Plant extracts are degradable

Second Generation Pesticides Primarily synthetic organic compounds Over 600 biologically-active compounds Broad-spectrum agents Toxic to many Narrow-spectrum agents Toxic to specific group Target species/Nontarget species See Table 20-1 p. 514

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 Do not harm other species Break down quickly Do not cause genetic resistance Are more cost-effective than doing nothing

Individuals Matter: Rachel Carson Wrote Silent Spring which introduced the U.S. to the dangers of the pesticide DDT and related compounds to the environment.

The Case Against Pesticides Genetic resistance Can kill nontarget and natural control species Can cause an increase in other pest species The pesticide treadmill Once started we must continue, often at higher and higher rates Pesticides do not stay put Can harm wildlife Potential human health threats

Pesticide Regulation in the United States Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Established 1947/Amended 1972 EPA reviews evaluation of chemicals Sets tolerance levels Inadequate and poorly enforced

Pesticide Regulation in the United States Food Quality Protection Act (FQPA) Established in 1996 New standards for pesticide tolerance based on no harm to human health

Other Ways to Control Pests Economic threshold The point at which economic losses caused by pest damage outweigh the cost of applying a pesticide. Adjusting cultivation practices Use genetically-resistant plants Biological pest control

Other Ways to Control Pests Biological pest control: Wasp parasitizing a gypsy moth caterpillar.

Other Ways to Control Pests Genetic engineering can be used to develop pest and disease resistant crop strains. Both tomato plants were exposed to destructive caterpillars. The genetically altered plant (right) shows little damage. Contains a gene from bacteria called the Bt gene.

Other Ways to Control Pests Biopesticides Insect birth control Hormones and pheromones Ionizing radiation

Integrated Pest Management Ecological system approach Reduce pest populations to economic threshold Field monitoring of pest populations Use of biological agents Chemical pesticides are last resort