Presentation on theme: " What is a Pesticide? Major Kinds of Pesticides Benefits and Problems With Pesticides Alternatives to Pesticides Laws Controlling Pesticides."— Presentation transcript:
What is a Pesticide? Major Kinds of Pesticides Benefits and Problems With Pesticides Alternatives to Pesticides Laws Controlling Pesticides Use
Types: Insecticides Herbicides Fungicides Rodenticides Regulated by the EPA
Broad spectrum pesticide kills a variety of organisms, not just the targeted organisms Doesn’t degrade = doesn’t decompose = persist and then accumulate in environment or organism.
o First generation pesticide Inorganic compounds Lead and mercury Botanicals- plant derived pesticides Nicotine Second generation pesticide Synthetic poison Ex: DDT for mosquitoes used to control malaria
Chlorinated Hydrocarbons Organic compound containing Chlorine Ex: DDT Persist (do not degrade) **Rachel Carson – “Silent Spring” = problems w/ pesticides Organophosphates Developed during WWII HIGHLY toxic (bees/humans), but do not persist Currently used in agriculture EX: Malathion, diazinon Neurotoxin, especially children Carbamates Not as toxic to mammals Ex: household sprays/traps RACHEL CARSON… ENVIRONMENTAL GODDESS
How are organophosphates different than chlorinated hydrocarbons?
Selective Herbicides Kill only certain types of plants Can be classified to the type of plant they kill Broad-leaf herbicides Ex: 2,4-D (2,4 dichlorophenoxyacetic acid) Ex: 2,4,5 –T (2,4,5, trichlorophenoxyacetic acid) Used with wheat, corn, rice (cereal grains = grasses) Grass herbicides Nonselective – kill all vegetation
When would you use a broad-leaf herbicide? A grass herbicide
Sprayed to kill vegetation – Agent White, Blue, Orange Ecological damage – decades to repair – destroyed mangroves (habitat for fish and coast protection from erosion), forests destroyed Human effects Agent Orange = (combination of broad leaf herbicides + dioxins) birth defects, stillbirths, cancer Dioxin in breastmilk – Vietnamese = 1800 ppt, US = 4 ppt
Benefit 1. : Disease control Fleas, lice and mosquitoes carry disease Malaria Malaria- mosquito born 2.7 million people die each year Few drugs available, so focus is on killing mosquitoes DDT
Benefit 2. : Crop Protection Pests eat and destroy 1/3 of world’s crops Farmers save $3 to $5 for every $1 they invest in pesticides
Problem: Evolution of Genetic Resistance Pest populations are evolving resistance to pesticides (right) Pesticide Treadmill Cost of applying pesticide increases Because they must be applied more frequently or in larger doses While their effectiveness decreases Because of increased genetic resistance in pests Resistance Management Refuge of untreated plants: allows mating of treated/untreated pests to delay resistance Remove surviving weeds after herbicide application
Problem: Kills non-target organisms Spraying to kill insects can kill birds, fish, bees Despite 33-fold increase in pesticides since the 1940s, crop loss has not really changed
Problem: Creation of New Pests Pesticide kills predator or competitor of minor pest
Problem: Persistence, Bioaccumulation, and Biological Magnification Bioaccumulation The buildup of a persistent pesticide or other toxic substance in an organisms body Biological magnification Increased concentration of toxic chemicals in tissues of organisms at higher trophic levels, stored in fat Ex: Peregrine falcons (right), Bald Eagles
Problem: Mobility in the Environment Do not stay where they are applied harm non-target organisms. Move through soil, water (run-off) and air
Effects of Pesticides Handling food with pesticide residue Mild case: nausea, vomiting, headaches Severe case: damage to nervous system (neurotoxin!!!)
Long-term Effects of Pesticides: Cancer- lymphoma and breast Sterility Miscarriage Birth defects Harms immune system
1984 Bhopal, India Explosion at pesticide plant released toxic gas (cyanide) Many died immediately Others: problems to respiratory, reproductive, nervous systems
Using cultivation methods to control pests Interplant mixtures of plants (alternating rows): polyculture !! Crop rotation Biological Control Use of naturally occurring disease organisms, parasites or predators to control pests Must take care that introduced agent does not attack unintended hosts CANE TOADS
Pheromones and Hormones Can use pheromones to lure pests to traps Reproductive Controls Sterilizing some of the members Sterile male technique: sterilize in lab and then release
IPM Combination of pest control methods that keeps pest population low without economic loss Controls pests, not eradicate Cons: requires a lot of knowledge Conventional pesticides are used sparingly when other methods fail HOW DOES IPM DIFFER FROM ORGANIC FARMING?
Farmers MONITOR pests and act when injury threshold is reached. EX: Cotton – 1% of land; 50% of pesticide use in US. – WOW!! Organic cotton helps reduce pesticide use.
Rice Production in Indonesia Predators of pests normally kept in check by pesticides IPM Introduced
Food, Drug, and Cosmetics Act (1938) –FDCA – determined pesticides need regulation! Delaney Clause (1958) – no cancer causing substances; not cover raw foods. Federal Insecticide, Fungicide, and Rodenticide Act (1947) – FIFRA – regulates what pesticides are sold based on safety. Food Quality Protection Act (1996) – stricter guidelines on pesticide limits, covers raw food, reduce time to ban harmful pesticide.
Some US companies still make banned or seriously restricted pesticides Product is exported Importation of food tainted with banned pesticides from other countries Global ban of persistent organic pollutants Stockholm Convention on Persistent Organic Pollutants (2004) – requires countries to eliminate usage of the 12 most toxic chemicals.
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