Pests and Pesticides Pest ANY troublesome destructive or

Pests and Pesticides

Pest • “ANY troublesome, destructive, or annoying organism” • Problems with pest: – Disease carrying – Compete with us for food Examples: – Fungi – Grasshopper – Boll weevil

Pesticides • • • Avicides Insecticides Fungicides Nematicides Herbicides

The History • Up until WWII, naturally produced pesticides were used but they were specific and did not cover all pests. • During WWII we used insects as test subjects for war chemicals, including nerve gases. It was at that time we concluded that the same chemicals (chlorinated hydrocarbons and organic phosphates) could be used as broad spectrum insecticides.

Chlorinated hydrocarbons • Became the most important group of insecticides. WHY? – – – – Cheap Easy to use Did not wash away Continued killing insects well after they were applied Killed a variety of insects Not very toxic to humans Example: DDT

Users of pesticides • You and me! • #1 user-Farmers

Are all insects, fungi, & worms pests? • NO! • Only about 1/8 th are considered pest and cause us problems, the rest are beneficial! • They enrich soil (earthworms & fungi), provide us with antibiotics and aid in food processing (fungi) and our crops are pollinated by them (bees & beetles)

Monoculture • Growing 1 plant species over many acres of property (example: corn or soybean or cotton, or grass on a golf course!) • Provides an abundant food source which increases carrying capacity of the insect

Pros for pesticides • Save lives that would have been lost due to the spread of disease • Decreased the amount of food lost both before harvest (35% of crops are lost before harvest) and during storage (15% lost during storage)

Cons for pesticides • Superbugs! Pg 253 – Changes occur in the DNA of some insects and give them the ability to make the chemicals harmless. Each time the insecticide is applied the more resistant the pest becomes

Cons • Persistent pesticides: chemicals not broken down by nature and can still be found in the soil years later – Chlorinated hydrocarbons are among the most persistent – DDT: was banned in the 70’s but still persist in the environment today • Carried by wind, water, in body fat and milk

Bioaccumulation • Pesticides that accumulate in the body tissues of organisms • The pesticide will move up the food chain and become more concentrated

Broad spectrum insecticides • Kill the intended pest but may also kill some insects that are not intended any harm (example: bees) • Alternative: Selective pesticides – Only kill one type of organism and doesn’t affect others