William P. Cunningham University of Minnesota Mary Ann Cunningham Vassar College Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Chapter 10 Lecture Outline *

Pests and Pesticides Biological Pests - organisms that reduce the availability, quality, or value of resources useful to humans Only about 100 species of organisms cause 90% of crop damage worldwide. Insects are most frequent pests. Make up three-fourths of all species Generalists Compete effectively against specialized endemic species

Pesticides Pesticide - chemical that kills pests Biocide - kills wide range of organisms Herbicide - kills plants Insecticide - kills insects Fungicide - kills fungi Acaricide - kills mites, ticks, and spiders Nematicide - kills nematodes Rodenticide - kills rodents Avicide - kills birds

Conventional Pesticide Use

Early Pest Controls Sumerians controlled insects with sulfur 5,000 years ago. Chinese describe mercury and arsenic to control pests 2,500 years ago. People have used organic compounds and biological controls for a long time. Romans burned fields and rotated crops to reduce crop disease.

DDT Era of synthetic organic pesticides began in 1939 with DDT. Inexpensive, stable, easily applied, highly effective By 1960’s, evidence of concentration through food chains. Carnivorous birds such as eagles suffered egg shell thinning leading to an inability to reproduce. In 1962, Rachel Carson published Silent Spring warning of the dangers.

DDT Banned in developed countries by late 1960’s; still used in developing countries Most prevalent contaminant on U.S. imported food The example of DDT highlights a more general problem with synthetic pesticides. Many of them have proven to have unintended consequences on non-target species.

Current Pesticide Use EPA estimates total pesticide use in the U.S. amounts to about 5.3 billion pounds annually. Roughly half is chlorine and hypochlorites used for water purification Roughly 80% of all conventional pesticides applied in the U.S. are used in agriculture or food storage and shipping. Remainder are used as preservatives in wood, leather and other materials

Use of Pesticides in the U.S.

Pesticide Types Inorganic Pesticides – broad-spectrum, generally highly toxic, and essentially indestructible (arsenic, copper) Generally neurotoxins Natural Organic Pesticides - generally plant extracts (nicotine, pyrethrum, turpentine) Fumigants - small molecules that gasify easily and penetrate materials rapidly (carbon tetrachloride, ethylene dibromide). Extremely dangerous; many have been banned.

Pesticide Types Chlorinated Hydrocarbons - fast acting and highly toxic to sensitive organisms (DDT, mothballs) Inhibit nerve membrane ion transport and block nerve signal transmission Persistent and concentrated in food chain Organophosphates - extremely toxic to mammals, birds and fish (Malathion) Inhibit cholinesterase, an enzyme necessary for nervous system function A single drop can be lethal, so dangerous to workers Quickly degraded

Pesticide Types Carbamates - similar to organophosphates (Sevin) - Extremely toxic to bees Halogenated pyrroles - new class of compounds based on a microbial toxin. Marketed as “Pirate.” Shown to reduce duck reproduction. Biological Controls and Microbial Agents - living organisms or toxins derived from them are used in place of pesticides Bacteria such as Bacillus thuringiensis kill beetles. Parasitic wasps such as Trichogramma kill moths.