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Unformatted text preview: 1 Pest Resistance Lecture 8 Wednesday,November 05, 2008 Resistance to Plant Pests: Natural Plant Encoded Pest Resistance Core Concepts : Introduction: The insect problem. Ubiquity and abundance of insects Chemical pesticides Cost and toxicity Secondary infestation Pesticide residue – ‘Silent spring’ Biological control Biopesticides Microbial pesticides Ubiquity and abundance of insects: Insects are earths most versatile organisms, ~51% of al species of living things are insects and ~78% of al species of animals are insects. Insects need C&N to survive and multiply, therefore, every living thing is potential y food and shelter for insects. However, in spite of the vast abundance of insects we stil have plants and other living things. This reality indicates the presence of genetic mechanisms in the environment to control insect populations - a balance of power. Chemical vs Biological Control Plant based Insect Resistance Mechanisms Insecticidal Proteins 2 Chemical pesticides: Chemical pesticides are used to control agricultural pests and in spite of the ~$8 billion spent worldwide there are significant crop losses due to insects (~$98 billion). It is estimated that about 13% of the total worldwide crop is lost despite the use of chemical pesticides. What are the features of an ideal insecticide? 1) great toxicity 2) rapid onset of toxic action 3) little or no toxicity to humans/animals/plants 4) non irritant-faint odor not unpleasant 5) range of action as wide as possible 6) good stability, long persistent action 7) low price. The widespread success of the chemical pesticide DDT can be evaluated by the world wide success in controlling Malaria and yellow fever in the 50's. The publication of ‘Silent Spring’ by Rachel Carson in 1962 alerted the public to the dangers of chemical pesticides and had a chilling effect on the use of DDT. For example in Ceylon spraying of DDT was stopped in 1964. Reported cases of malaria had fallen to 17 in 1963 (from 2,800,000 in 1948 when spraying was initiated), by 1969 the number of cases was up, 2,500,000, back to the 1948 levels. Today malaria is live and well with over 500,000 infected individuals worldwide. Estimated pesticide material and application costs for the control of codling moth in walnut or apple orchards. cost/acre/application Chemical # of applications Material Application WALNUTS Guthion 1-3 $18 $15 Lorsban 1-3 $18 $15 Supracide 1-2 $40 $15 APPLES Guthion 2-4 $18 $15 Imidan 2-4 $18 $15 Estimated pesticide material and application costs for the control of codling moth in walnut or apple orchards. cost/acre/application Chemical # of applications Material Application WALNUTS Guthion 1-3 $18 $15 Lorsban 1-3 $18 $15 Supracide 1-2 $40 $15 APPLES Guthion 2-4 $18 $15 Imidan 2-4 $18 $15 Common pesticides used in codling moth control and their relative toxicity in rats....
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This note was uploaded on 12/03/2010 for the course ECONOMY Eco 100 taught by Professor Taidat during the Spring '10 term at Hanoi University of Technology.
- Spring '10