Pests, Plagues & Politics Lecture 15 Chemical Control Pre- & Post DDT

Xenophon Student of Socrates “ Crop protection is in the hands of the Gods.”

Key Points: Chemical control Important ancient pesticides Botanical insecticides Underlying reason for development of synthetic insecticides Advantages/Disadvantages of DDT Define Integrated Pest Management (IPM)

Pesticide(s) Include –Insecticides –Herbicides –Fungicides –Rodenticides –et alia

Early/ancient Insecticides of Value Tobacco & other botanicals Soapsuds [renewed with Safer’s Soap ] Fish & Whale oil –known as DORMANT OIL Dusts –charcoal & soot –sulfur & ground tobacco –lime powder –Plaster of Paris (ground)

The Botanicals Tobacco (nicotine) Rotenone (So. American) Hellebore ( France) Pyrethrum - the most famous!!! –From a daisy –native to the Caucasus Mts. of eastern Europe –1 st commercialized in Armenia in 1807 –1 st U.S. in still viable today. –Ragwort - alkaloids

The pyrethrum daisy Chrysanthemum cinerarifolium

First Synthetic Insecticides (the inorganics) Bordeaux Mix (hydrated lime & copper sulfate) Paris Green (copper acetoarsenite) The elementals –Antimony - Arsenic - Mercury - Selenium Hydrocyanic gas (a fumigant in citrus - ca. 1880)

Synthetic Organic Insecticides World War II - major problem with insect vectored disease *“ Arbor ” disease {ARthropod BORne) –malaria, typhus, dengue fever, encephalitis Major effort to find effective insecticides USDA - evaluated DDT from the Swiss Geigy Company.

DDT EUREKA !!! - with even minute doses it killed every bug tested. Silver Bullet –Potentially the “Silver Bullet” Chemical analysis showed it to be: –*DDT –*D ichloro- D iphenyl- T richloroethane –a chlorinated hydrocarbon (CH) –first synthesized in 1874 by Othmar Zeilder in Germany Between 1941 & 1976 over 4.5 million tons produced (about 1.5 pound for every living human on earth today)

DDT PlusesPluses: –wide spectrum of insecticidal action –simple structure & easy (& cheap) to manufacture –prolonged stability & residual activity –low mammalian toxicity

 "The great expectations held for DDT have been realized. During 1946, exhaustive scientific tests have shown that, when properly used, DDT kills a host of destructive insect pests, and is a benefactor of all humanity." TIME MAG

Lots of options

DDT – so what happened? Went from an EFFECTIVE tool in medical entomology toWent from an EFFECTIVE tool in medical entomology to Overused & Abused tool in agricultural entomologyOverused & Abused tool in agricultural entomology

Bio-magnificationBio-accumulation ogy/toxicology.htm

Chlorinated Hydrocarbons (CHs) DDTSuccess of DDT led to the development of additional CHs: –Lindane, Dieldrin, Chlordane, Methoxychlor, Heptachlor Prime characteristic being –Environmental Persistence CHs are lipophilic & were eventually spread throughout “spaceship earth”

Organophosphates (OPs) Concurrent with the development of CH insecticides was work on another group. OPsThe OPs –extremely toxic in small doses ( hot ) –high mammalian & avian toxicity –less persistent in the environment Malathion, Parathion et alia In 1932, German chemist Willy Lange and his graduate student, Gerde von Krueger, first described the cholinergic nervous system effects of organophosphates, noting a choking sensation and a dimming of vision after exposure.

Problems with synthetics OVERUSEOVERUSE –environmental buildup NON-SPECIFICITYNON-SPECIFICITY –toxic to many taxa, including non-target insects –removal of beneficial insect complexes RESISTANCE DEVELOPMENTRESISTANCE DEVELOPMENT –over time a given insecticide loses effectiveness against the target pest insect

Insecticide Resistance 1945: E.H. Strickland writes: – “Could the Widespread Use of DDT be a Disaster?” houseflies resistant to DDT (Sweden) cases of documented resistance cases!!!

Things Have Changed ECONOMICSECONOMICS –many fewer pesticides now (EPA restrictions & cost of P-cide development) EVER GROWING ENVIRONMENTAL ETHICEVER GROWING ENVIRONMENTAL ETHIC –in the field of economic entomology –by the government (EPA, ODE) NEW GENERATIONS OF INSECTICIDESNEW GENERATIONS OF INSECTICIDES –ENVIRONMENTALLY SAFER –MORE TARGET SPECIFIC –VERY COSTLY

4 th Generation Insecticides Insect Growth Regulator ‘mimics’ –Hormones that interfere with an insect’s growth & development GMO –Bt corn, cotton, et alia –Developing problems here with resistance

INTEGRATED PEST MANAGEMENT IPM Commencing in the 1960 ties The use of multiple techniques & strategies to control pest insect populations below an economic level Chemicals are still used, but in combination with other methods in a broader understanding of a pest insect’s life history

Key Points: Chemical control Important ancient pesticides Botanical insecticides Underlying reason for development of synthetic insecticides Advantages/Disadvantages of DDT Define Integrated Pest Management (IPM)