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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
Insecticides
  • A Brief Overview of a Complex Subject
modes of entrance into insect
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
Mode of Toxicity in Insects
  • Physical poison
  • General protoplasmic poison
  • Cellular enzyme poison
  • Nerve poison
  • Growth regulator
  • Disease causing agent
  • Repellant
toxicity to humans or nontarget organisms
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
toxicity to insects natural enemies
Toxicity to insects natural enemies
  • Most insecticides have the potential to affect populations of beneficial insects.
toxicity to insects natural enemies1
Toxicity to insects natural enemies

Highly toxic - Pest populations recover much faster than enemy populations in nature

toxicity to insects natural enemies2
Toxicity to insects natural enemies

Moderately toxic – Pest populations recover somewhat faster than enemy populations in treated environment

toxicity to insects natural enemies3
Toxicity to insects natural enemies

Low toxicity – Natural enemies are maintained to a degree & quickly attack recovering pest populations

toxicity to insects natural enemies4
Toxicity to insects natural enemies
  • Nontoxic – Normal enemy population levels are maintained which quickly attack recovering pest populations
environmental hazard
Environmental hazard
  • Environmental hazard of insecticides is generally evaluated as a function of persistence often compared to effectiveness
environmental hazard1
Environmental hazard

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

environmental hazard2
Environmental hazard

Intermediate – Persists beyond effectiveness (3-5 month half-life)

environmental hazard3
Environmental hazard

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

environmental hazard4
Environmental hazard

Very low – Persists for short periods (>45 days) and degrades completely

resistance resurgence hazard
Resistance/Resurgence Hazard
  • The hazard of populations developing resistance and resurging is evaluated for most insecticides
resistance resurgence hazard1
Resistance/Resurgence Hazard

High – Strong potential to develop resistance and resurge

resistance resurgence hazard2
Resistance/Resurgence Hazard

Intermediate – Moderate potential to develop resistance in treated environments

resistance resurgence hazard3
Resistance/Resurgence Hazard

Low – Minimal potential to develop resistance

resistance resurgence hazard4
Resistance/Resurgence Hazard

None – No resistance developed, no resurgence after many treatments

ipm attributes
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
ipm attributes1
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
insecticide groups
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
organochlorines
Organochlorines
  • Also called the chlorinated hydrocarbon insecticides
organochlorines1
Organochlorines
  • Characterized by containing chlorine and carbon atoms
organochlorines2
Organochlorines
  • Powerful nerve poisons
organochlorines3
Organochlorines
  • Most affect a broad spectrum of non-target organisms along with the target pests
organochlorines4
Organochlorines
  • Biochemical mode of action – uncertain
organochlorines5
Organochlorines
  • Mode of action chemical dependant
organochlorines6
Organochlorines
  • Long persistence and residual activity
organochlorines7
Organochlorines
  • Several were used in forestry
    • DDT
    • Lindane
    • Dicofol (Kelthane)
    • Endosulfan (Thiodan)
organochlorines8
Organochlorines
  • Most have been banned in the U.S.
organochlorines9
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
organophosphates
Organophosphates
  • Also known as the OPs
organophosphates1
Organophosphates
  • Characterized by containing carbon and phosphorus atoms
organophosphates2
Organophosphates
  • Chemical and often habitat dependant effect on non-target organisms
organophosphates3
Organophosphates
  • Mode of action varies by chemical
organophosphates4
Organophosphates
  • Generally only short term persistence and limited residual activity
organophosphates5
Organophosphates
  • Unfortunately, often have broad spectrum activity against beneficial insects
organophosphates6
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)
organophosphates7
Organophosphates
  • Most have been lost to forestry due to FQPA (Food Quality Protection Act) review performed by the EPA
organosulfurs
Organosulfurs
  • Small group of sulfur containing insecticides
organosulfurs1
Organosulfurs
  • Low insect toxicity, but with good miticidal characteristics
organosulfurs2
Organosulfurs
  • Have been used in seed orchard work
organosulfurs3
Organosulfurs
  • Only a single product relevant to this discussion
    • Propargite (Omite)
carbamates
Carbamates
  • Insecticides which are derivatives of carbamic acid
carbamates1
Carbamates
  • Non-target toxicity is chemical specific, ranging from low to very high
carbamates2
Carbamates
  • Generally only short term persistence and limited residual activity
carbamates3
Carbamates
  • Often with broad spectrum activity against beneficial insects
carbamates4
Carbamates
  • Very few used in forestry
    • Carbaryl (Sevin)
    • Aldicarb (Temik)
    • Methomyl (Lannate)
botanicals
Botanicals
  • Chemicals extracted or derived from plants
botanicals1
Botanicals
  • May be present and subsequently extracted from the plant material (a constitutive chemical), or
botanicals2
Botanicals
  • May be activated in the plant as a response to insect activity (inducible chemicals)
botanicals3
Botanicals
  • Limited numbers of extractable chemicals have performed well enough to have been made commercially available
botanicals4
Botanicals
  • Some are chemically modified after extraction to enhance their insecticidal properties
botanicals5
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)
synthetic pyrethroids
Synthetic Pyrethroids
  • Modified esters of chrysanthemate a chemical similar to that which is derived from chrysanthemums
synthetic pyrethroids1
Synthetic Pyrethroids
  • Alterations in the acid components yield a reduced degradation rate compared to natural pyrethrins
synthetic pyrethroids2
Synthetic Pyrethroids
  • Often with additional modification to enhance synergistic action
synthetic pyrethroids3
Synthetic Pyrethroids
  • Rates are often 10% of the rates of OPs
synthetic pyrethroids4
Synthetic Pyrethroids
  • Several have been used in forestry, seed orchard or nursery work
    • Permethrin (Pounce, Ambush, Dragnet)
    • Cypermethrin (Ammo)
    • Esfenvalerate (Asana)
    • Lamda cyhalothrin (Karate)
synergists or activators
Synergists or activators
  • Chemicals which perform any of a variety of actions which enhance the action of an insecticide
synergists or activators1
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
synergists or activators2
Synergists or activators
  • Two primary chemicals used in insecticide formulation
    • Piperonyl butoxide
    • Sesamin
soaps and abrasives
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)
soaps and abrasives1
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
soaps and abrasives2
Soaps and Abrasives
  • Soft soaps made from vegetable oils are most common at the present time due to a better smell (not greater efficacy)
soaps and abrasives3
Soaps and Abrasives
  • Soften or wash off the waxy epicuticle covering an insect allowing it to dehydrate
soaps and abrasives4
Soaps and Abrasives
  • Abrasives degrade the epicuticle - same result
soaps and abrasives5
Soaps and Abrasives
  • Two soaps are commonly used
    • Potassium salts of fatty acids (Safer soaps, M-Pede)
    • Boric acid
soaps and abrasives6
Soaps and Abrasives
  • A single abrasive is currently registered as a forestry insecticide
    • Borax
microbial pathogens
Microbial Pathogens
  • Fungi, bacteria, viruses, etc. which can be used to cause disease in an insect population
microbial pathogens1
Microbial Pathogens
  • Relatively narrow spectrum of activity, not broad spectrum insecticides
microbial pathogens2
Microbial Pathogens
  • Several have been genetically engineered to kill target insects more rapidly
microbial pathogens3
Microbial Pathogens
  • Bacteria in forestry
    • Bacillus thuringiensis var. karstaki (Dipel, Thuricide, Foray, Agrobac, Javelin, Cutlass)
microbial pathogens4
Microbial Pathogens
  • Virus in forestry
    • Baculovirus (Nucleopolyhedrosis virus or NPV; Gypchek, TM-Biocontrol-1)
microbial pathogens5
Microbial Pathogens
  • Bacteria applied over forests for public health protection
    • Bacillus thuringiensis var. israeliensis
    • Bacillus sphaericus
microbial derivatives
Microbial Derivatives
  • Generally organic chemicals with a nitrogen component
microbial derivatives1
Microbial Derivatives
  • Microbially produced and then extracted and refined
microbial derivatives2
Microbial Derivatives
  • Some are toxic to the target organisms at very low doses
microbial derivatives3
Microbial Derivatives
  • Only one used in forestry at present
    • Avermectin (derived from Streptomyces avermitilis)
    • Also available are:
      • spinosad (Tracer)
      • pyrroles (Pirate)
repellants
Repellants
  • Large group of unrelated chemicals
repellants1
Repellants
  • Many experimental chemicals – but to the present no truly effective forest protectant chemical
repellants2
Repellants
  • Mostly have found use for people or livestock protection
repellants3
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
repellants4
Repellants
  • Forester protective repellant
    • Deet (Off, Deep-Woods-Off)
slide86
Oils
  • Lightweight petroleum oils mixed with emulsifiers may be used as insecticides in some cases
slide87
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
slide88
Oils
  • Oils kill by suffocation (scales, mealy bugs and aphids)
slide89
Oils
  • Forestry registered oils include
    • Sunspray
    • Superior oil
fumigants
Fumigants
  • Primarily used in forest tree nursery beds and greenhouses
fumigants1
Fumigants
  • Fumigants generally contain a halogen (chlorine, bromine, fluorine, etc.) in their molecules
fumigants2
Fumigants
  • Small molecules which vaporize at relatively low temperatures
fumigants3
Fumigants
  • Many are now or will shortly be banned in the US
fumigants4
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)
transgenic crops with insecticidal properties
Transgenic Crops with Insecticidal Properties
  • Plants genetically engineered to enhance insecticidal properties