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 - LD – 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

51. Botanicals
May be present and subsequently extracted from the plant material (a constitutive chemical), or

52. Botanicals
May be activated in the plant as a response to insect activity (inducible chemicals)

53. Botanicals
Limited numbers of extractable chemicals have performed well enough to have been made commercially available

54. Botanicals
Some are chemically modified after extraction to enhance their insecticidal properties

55. Botanicals
Only a few have found a niche in forestry, and generally even these are subsequently replaced by more target-specific, less persistent synthetic chemicals
Pyrethrins
Resmethrin (Pyosect, Synthhrin)
Azadirachtin (Azatin)

56. Synthetic Pyrethroids
Modified esters of chrysanthemate a chemical similar to that which is derived from chrysanthemums

57. Synthetic Pyrethroids
Alterations in the acid components yield a reduced degradation rate compared to natural pyrethrins

58. Synthetic Pyrethroids
Often with additional modification to enhance synergistic action

59. Synthetic Pyrethroids
Rates are often 10% of the rates of OPs

60. Synthetic Pyrethroids
Several have been used in forestry, seed orchard or nursery work
Permethrin (Pounce, Ambush, Dragnet)
Cypermethrin (Ammo)
Esfenvalerate (Asana)
Lamda cyhalothrin (Karate)

61. Synergists or activators
Chemicals which perform any of a variety of actions which enhance the action of an insecticide

62. Synergists or activators
Increase the toxicity of the initial chemical above that expected from the combination of the two products
Block detoxification of insecticides by insect defensive systems
Induce the functioning of otherwise benign chemicals

63. Synergists or activators
Two primary chemicals used in insecticide formulation
Piperonyl butoxide
Sesamin

64. Soaps and Abrasives
Produced by rending (cooking) animal fat (lard), fish oil or vegetable oil with an alkali metal such as sodium hydroxide (= hard soap) or potassium hydroxide (= soft soap)

65. Soaps and Abrasives
Soft soaps from fish oils were the most common insecticidal soaps in the past since they are the most effective insecticidal soaps

66. Soaps and Abrasives
Soft soaps made from vegetable oils are most common at the present time due to a better smell (not greater efficacy)

67. Soaps and Abrasives
Soften or wash off the waxy epicuticle covering an insect allowing it to dehydrate

68. Soaps and Abrasives
Abrasives degrade the epicuticle - same result

69. Soaps and Abrasives Two soaps are commonly used
Potassium salts of fatty acids (Safer soaps, M-Pede)
Boric acid

70. Soaps and Abrasives
A single abrasive is currently registered as a forestry insecticide
Borax

71. Microbial Pathogens
Fungi, bacteria, viruses, etc. which can be used to cause disease in an insect population

72. Microbial Pathogens
Relatively narrow spectrum of activity, not broad spectrum insecticides

73. Microbial Pathogens
Several have been genetically engineered to kill target insects more rapidly

74. Microbial Pathogens Bacteria in forestry
Bacillus thuringiensis var. karstaki (Dipel, Thuricide, Foray, Agrobac, Javelin, Cutlass)

75. Microbial Pathogens Virus in forestry
Baculovirus (Nucleopolyhedrosis virus or NPV; Gypchek, TM-Biocontrol-1)

76. Microbial Pathogens
Bacteria applied over forests for public health protection
Bacillus thuringiensis var. israeliensis
Bacillus sphaericus

77. Microbial Derivatives
Generally organic chemicals with a nitrogen component

78. Microbial Derivatives
Microbially produced and then extracted and refined

79. Microbial Derivatives
Some are toxic to the target organisms at very low doses

80. Microbial Derivatives
Only one used in forestry at present
Avermectin (derived from Streptomyces avermitilis)
Also available are:
spinosad (Tracer)
pyrroles (Pirate)

81. Repellants
Large group of unrelated chemicals

82. Repellants
Many experimental chemicals – but to the present no truly effective forest protectant chemical

83. Repellants
Mostly have found use for people or livestock protection

84. Repellants Forestry insect repellants include Verbenone
4-allyl anisole (4AA)
Both are anti-aggregant chemicals designed to disrupt pine beetle aggregation and thwart ‘spot’ formation

85. Repellants
Forester protective repellant
Deet (Off, Deep-Woods-Off)

86. Oils
Lightweight petroleum oils mixed with emulsifiers may be used as insecticides in some cases

87. Oils Broadly defined in two groups:
Dormant oils are designed to be used to protect dormant plant materials and may have bad effects if used during the growing season
Summer oils may be used to protect growing plants l

88. Oils
Oils kill by suffocation (scales, mealy bugs and aphids)

89. Oils
Forestry registered oils include
Sunspray
Superior oil

90. Fumigants
Primarily used in forest tree nursery beds and greenhouses

91. Fumigants
Fumigants generally contain a halogen (chlorine, bromine, fluorine, etc.) in their molecules

92. Fumigants
Small molecules which vaporize at relatively low temperatures

93. Fumigants
Many are now or will shortly be banned in the US

94. Fumigants
Fumigants which have held forestry or ornamental insecticide registration
Methyl bromide (MC33, MC98, Brom-o-Sol, etc.) – NFTA should eliminate this fumigant from the US by 2005
Dichloropropene
Chloropicrin
Metam-sodium (Vapam, Busan, Sectagon)

95. Transgenic Crops with Insecticidal Properties
Plants genetically engineered to enhance insecticidal properties

96. Transgenic Crops with Insecticidal Properties
None in forestry as yet