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Insecticides

Insecticides. A Brief Overview of a Complex Subject. Modes of Entrance into Insect. Contact - dermal – through the skin Stomach - oral – through the mouth Respiration - inhalation through the nose or gills Systemic - combination of above. Mode of Toxicity in Insects. Physical poison

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Insecticides

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  1. Insecticides • A Brief Overview of a Complex Subject

  2. Modes of Entrance into Insect • Contact - dermal – through the skin • Stomach - oral – through the mouth • Respiration - inhalation through the nose or gills • Systemic - combination of above

  3. Mode of Toxicity in Insects • Physical poison • General protoplasmic poison • Cellular enzyme poison • Nerve poison • Growth regulator • Disease causing agent • Repellant

  4. Toxicity to humans or nontarget organisms • Most insecticides have the capacity to affect non-target organisms • Same as previously discussed • Highly toxic – LD50 0 – 50 mg/kg • Moderately toxic - LD50 50 – 500 mg/kg • Low toxicity - LD50 500 – 5,000 mg/kg • Nontoxic - LD50 <5,000 mg/kg

  5. Toxicity to insects natural enemies • Most insecticides have the potential to affect populations of beneficial insects.

  6. Toxicity to insects natural enemies Highly toxic - Pest populations recover much faster than enemy populations in nature

  7. Toxicity to insects natural enemies Moderately toxic – Pest populations recover somewhat faster than enemy populations in treated environment

  8. Toxicity to insects natural enemies Low toxicity – Natural enemies are maintained to a degree & quickly attack recovering pest populations

  9. Toxicity to insects natural enemies • Nontoxic – Normal enemy population levels are maintained which quickly attack recovering pest populations

  10. Environmental hazard • Environmental hazard of insecticides is generally evaluated as a function of persistence often compared to effectiveness

  11. Environmental hazard High – Environmental persistence far greater than period of effectiveness (> 5 months and often > a year)

  12. Environmental hazard Intermediate – Persists beyond effectiveness (3-5 month half-life)

  13. Environmental hazard Low – Persists about the period of effectiveness (up to about 3 months) and then degrades completely over several months

  14. Environmental hazard Very low – Persists for short periods (>45 days) and degrades completely

  15. Resistance/Resurgence Hazard • The hazard of populations developing resistance and resurging is evaluated for most insecticides

  16. Resistance/Resurgence Hazard High – Strong potential to develop resistance and resurge

  17. Resistance/Resurgence Hazard Intermediate – Moderate potential to develop resistance in treated environments

  18. Resistance/Resurgence Hazard Low – Minimal potential to develop resistance

  19. Resistance/Resurgence Hazard None – No resistance developed, no resurgence after many treatments

  20. IPM Attributes • IPM is especially important when discussing the use of insecticides due to the potential for the development of resistance and subsequent resurgence of pest populations repeatedly treated with a single insecticide • Repeated treatment with a single pesticide imposes artificial genetic selection on insect populations

  21. IPM Attributes • However, IPM must be effective and so there are several criteria to evaluate • Effectiveness in controlling pest populations • Cost of treatment • Human and nontarget-animal toxicity • Environmental persistence

  22. Insecticide groups • The following slides present a system in which insecticides are generally catagorized • It is not the only system • Lumpers and splitters of names have created very different categories, depending on their emphasis

  23. Organochlorines • Also called the chlorinated hydrocarbon insecticides

  24. Organochlorines • Characterized by containing chlorine and carbon atoms

  25. Organochlorines • Powerful nerve poisons

  26. Organochlorines • Most affect a broad spectrum of non-target organisms along with the target pests

  27. Organochlorines • Biochemical mode of action – uncertain

  28. Organochlorines • Mode of action chemical dependant

  29. Organochlorines • Long persistence and residual activity

  30. Organochlorines • Several were used in forestry • DDT • Lindane • Dicofol (Kelthane) • Endosulfan (Thiodan)

  31. Organochlorines • Most have been banned in the U.S.

  32. Organochlorines • Very few still available for our use • Endosulfan is sometimes used on ornamentals and in seed orchards • Lindane is still registered for Southern Pine Beetle control but no product is available in the marketplace

  33. Organophosphates • Also known as the OPs

  34. Organophosphates • Characterized by containing carbon and phosphorus atoms

  35. Organophosphates • Chemical and often habitat dependant effect on non-target organisms

  36. Organophosphates • Mode of action varies by chemical

  37. Organophosphates • Generally only short term persistence and limited residual activity

  38. Organophosphates • Unfortunately, often have broad spectrum activity against beneficial insects

  39. Organophosphates • Several used in forestry or applied to forests for public health purposes • Malthion (Malathion and Cythion) • Acephate (Orthene) • Methyl parathion (Methyl parathion) • Diazinon (Diazinon and Spectracide) • Chlorpyrifos (Dursban and Lorsban) • Azinphos methyl (Guthion)

  40. Organophosphates • Most have been lost to forestry due to FQPA (Food Quality Protection Act) review performed by the EPA

  41. Organosulfurs • Small group of sulfur containing insecticides

  42. Organosulfurs • Low insect toxicity, but with good miticidal characteristics

  43. Organosulfurs • Have been used in seed orchard work

  44. Organosulfurs • Only a single product relevant to this discussion • Propargite (Omite)

  45. Carbamates • Insecticides which are derivatives of carbamic acid

  46. Carbamates • Non-target toxicity is chemical specific, ranging from low to very high

  47. Carbamates • Generally only short term persistence and limited residual activity

  48. Carbamates • Often with broad spectrum activity against beneficial insects

  49. Carbamates • Very few used in forestry • Carbaryl (Sevin) • Aldicarb (Temik) • Methomyl (Lannate)

  50. Botanicals • Chemicals extracted or derived from plants

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