Insecticides

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