Chapter 23 The Pesticide Dilemma

Pests  Pest – any organism that interferes in some way with human welfare or activities grouped by target organism they attack grouped by target organism they attack  Insecticides – kills insects  Herbicides – kills plants  Fungicides – kills fungus  Rodenticides – kills rodents

Agriculture  Sector that uses the most pesticides (85% world wide)  Narrow spectrum pesticides – pesticides that kill only the organism for which it was intended.  Broad spectrum pesticides – pesticides that kill a wide variety of organisms.  Additional problems with pesticides – more in environment, don’t degrade.

What is a Pesticide  Broad spectrum pesticide  A pesticide that kills a variety of organisms, not just the targeted organisms  First generation pesticide  Inorganic compounds  Lead, mercury and arsenic  Organic compounds (Botanicals- plant derived pesticides)  Nicotine and pyrethrin

What is a Pesticide  Second generation pesticide  Synthetic poison  Ex: DDT

Major Groups of Insecticides  Chlorinated Hydrocarbons  Organic compound containing Chlorine  Ex: DDT  Slow to degrade and persist in the environment  Banned or largely restricted  Endosulfan, lindane & methoxychlor still in use  Organophosphates  Organic compounds that contain phosphorus  Most poisonous insecticide  Very poisonous & toxic to birds, bees and aquatic organisms organisms  Do not persist as long as chlorinated hydrocarbons  Cabamates  Derived from cabamic acid, not toxic to mammals, broad spectrum

Major Kinds of Herbicides  Selective Herbicides  Kill only certain types of plants  Can be classified to the type of plant they kill  Broad-leaf herbicides-which kill broad-leaf plants but not grasses  Grass herbicides-kill grasses but not other plants  Ex: 2,4-D  Non selective herbicides-kills all vegetation  Famous example – Agent Orange: mixture of two herbicides that contain dioxins includes a variety of health effects: tissue cancer, skin diseases, urological disorders & birth defects includes a variety of health effects: tissue cancer, skin diseases, urological disorders & birth defects

Benefits and Problems with Pesticides  Benefit: Disease control, crop protection  Fleas, lice and mosquitoes carry disease  Malaria- mosquito born  2.7 million people die each year  Few drugs available, so focus is on killing mosquitoes  DDT

Benefits and Problems with Pesticides  Benefit: 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  Strategies for managing genetic resistance in order to maximize the period in which a pesticide is useful  Delays the evolution of genetic resistance  Refuge of untreated plants-leave some population untouched to prevent resistance Pesticide Resistance

Benefits and Problems with Pesticides  Problem: Imbalances the Ecosystem  Spraying to kill insects can affect birds, rabbits, etc.  Despite 33-fold increase in pesticides since the 1940s, crop loss has not really changed

Benefits and Problems with Pesticides  Problem: Creation of New Pests  Infestation of red scale insects on lemons after DDT sprayed to control another pest

Benefits and Problems with Pesticides  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  Ex: Peregrine falcons (right)

Benefits and Problems with Pesticides  Problem: Mobility in the Environment  Do not stay where they are applied  Move through soil, water and air

Risk of Pesticides to Human Health  Short-term Effects of Pesticides  Handling food with pesticide residue  Mild case: nausea, vomiting, headaches  Severe case: damage to nervous system  Lead-neurological development  Mercury- biomagnification via fish and crabs

Risk of Pesticides to Human Health  Long-term Effects of Pesticides  Cancer- lymphoma  Breast cancer  Sterility  Miscarriage  Birth defects  Decreases body’s ability to fight infection  Potential connection to Parkinson’s disease

Alternatives to Pesticides  Using cultivation methods to control pests  Interplant mixtures of plants (alternating rows)  Strip cutting-leaving strips of un-harvested crops  Proper timing of planting, fertilizing, and irrigating  Crop rotation  Biological Control  Use of naturally occurring disease organisms, parasites or predators to control pests (such as lady bugs and praying mantises)  Must take care that introduced agent does not attack unintended hosts

Alternatives to Pesticides  Pheromones and Hormones  Can use pheromones to lure pests to traps  By applying insect hormones at wrong time in life cycle, insects can be killed off  Reproductive Controls  Sterilizing some of the members  Sterile male technique  Genetic Controls  Genetically Modified plants (GMOs)  Bt toxin  Potential problem: may affect non-target species (monarch butterfly)  Quarantine  Restriction of the importation of exotic plant and animal material that might harbor pests  Effective, but not foolproof

Systems Approach- Integrated Pest Management (IPM)  IPM  Combination of pest control methods that keeps pest population low without economic loss  Conventional pesticides are used sparingly when other methods fail IPM uses 3 premises 1. Management rather than eradication 2. Economic injury-don’t take action until this point, use non toxic first 3. Education-educate farmers as to all the alternatives Scout and spray-monitor for pests & only spray when they become a problem Calendar Spraying-regular spraying whether need or not

 Rice Production in Indonesia Systems Approach- Integrated Pest Management (IPM) IPM Introduced

Alternatives to Pesticides  Irradiating Food  Harvested food is expose to ionizing radiation, which kills many microorganisms  Predominantly used on meats  Somewhat controversial due to potential for free radicals

Laws Controlling Pesticide Use  Food, Drug, and Cosmetics Act (1938) recognized need to regulate pesticides but had no teeth recognized need to regulate pesticides but had no teeth  Pesticide Chemicals Amendment (1954) established acceptable levels of pesticides in food established acceptable levels of pesticides in food  Delaney Cause (1958) prohibits cancer-causing substances in food (applies only to pesticides) prohibits cancer-causing substances in food (applies only to pesticides)  Federal Insecticide, Fungicide, and Rodenticide Act (1947) regulated pesticide sale to prevent the sale of lemon (pesticides that don’t work) regulated pesticide sale to prevent the sale of lemon (pesticides that don’t work) requires disclosure of active ingredients but not inert ingredients requires disclosure of active ingredients but not inert ingredients  Food Quality Protection Act (1996) Established pesticide residue limits in both raw and processed foods Established pesticide residue limits in both raw and processed foods

Manufacture and Use of Banned Pesticides  Some US companies still make banned or seriously restricted pesticides  Product is exported  May lead to the importation of food tainted with banned pesticides  Global ban of persistent organic pollutants  Stockholm Convention on Persistent Organic Pollutants (2004)  Stockpiles of banned pesticides, predominantly in developing countries

Manufacture and Use of Banned Pesticides