Lecture #2 Benefits and Problems resulting from Pesticide Use Chapter 10 Pest Control Lecture #2 Benefits and Problems resulting from Pesticide Use

Pesticide Benefits Disease Control Many insects serve as disease vectors. Anopheles mosquito spreads malaria. Crop Protection Using pesticides, pre-harvest losses to diseases and pests are at 33%, with post-harvest losses at an additional 20-30%. Losses would be much higher without pesticides. In general, farmers save an average of $3-$5 for every $1 spent on pesticides.

Pesticide Problems Non-Target Species Up to 90% of pesticides never reach intended target and many beneficial organisms are killed. Pesticide Resistance and Pest Resurgence Resistant members of a population survive pesticide treatment and produce more resistant offspring. Pest Resurgence Pesticide Treadmill - as pests become resistant, we must develop new pesticides.

Creation of New Pests Broadcast spraying is also likely to kill beneficial predators. Under normal conditions many herbivorous pests are controlled by natural predators. When we kill the predators, we release the pests from their natural controls. With advent of chemical pest controls, farmers have tended to abandon traditional methods of pest/pathogen control such as crop rotation.

Environmental Persistence and Mobility Because chlorinated hydrocarbons (DDT) are so persistent, they tend to show up far from the point of dispersal. Stored in fat and tend to bioaccumulate High levels detected in upper levels of food chain Accumulate in polar regions due to the “grasshopper effect”. Evaporate from warm regions, condense in cold regions

Environmental Persistence and Mobility Many persistent organic pollutants were banned globally in 2001. Use was previously banned or restricted in developed countries, but U.S. companies continued to sell POPs in underdeveloped countries where regulations were lax. Many pesticides then returned to U.S. in agricultural products and migrating wildlife. Since the treaty banning POPs, other pesticides have taken their place.

Human Health Problems WHO estimates 25 million people suffer pesticide poisoning, and 20,000 die each year. At least 2/3 of these result from occupational hazards in developing countries. Long-term health effects difficult to conclusively document. PCBs in Great Lakes fish have been linked to learning deficiencies in children whose mothers ate the fish. Children whose homes are fumigated are 3X more likely to get acute lymphocytic leukemia. Is autism linked to environmental toxins?