Insect toxicology - insecticide mode of action

Dr. Jim Ottea, LSU AgCenter Department of Entomology

10:30 to 11:15

Why Understand Mode of Action?• Optimize insecticide use

• Increase safety

Insecticides Are Nerve Poisons

• Nervous system is a rich source of target sites• Effects are rapid• Actions are lethal

In the beginning…

Eventually…

Avoid Resistance by…

• Limiting insecticide applications• Select insecticides that preserve beneficial

insects• Follow the instructions on the label• If application fails, use an insecticide from a

different chemical classhttp://www.irac-online.org

Naming Insecticides I• Trade Names: capitalized, with ®• Each insecticide may have many• Example: Karate®

Demand®

Warrior®

Rice Insecticides: Trade Names

• Proaxis®, Prolex®, Trebon®, Karate®, Mustang Max®

• Orthene®, Malathion 57EC®, Cheminova Methyl 4EC®, Sevin®

• Cruiser®• Dermacor®, Rynaxypyr®, • Dimilin®

Naming Insecticides II

• Common names: not capitalized• Each insecticide has only one• Example: lamda- cyhalothrin

Rice Insecticides: Common Names

• - cyhalothrin, etofenprox, - cyhalothrin, zeta-cypermethrin• acephate, malathion, methyl parathion• carbaryl• thiamethoxam• chlorantraniliprole• diflubenzuron

Naming Insecticides III

• Chemical class: insecticides with common structural features

• Not absolute, but almost• Example: lambda- cyhalothrin is a pyrethroid

Rice Insecticides: Classes• Pyrethroids (e.g., cyhalothrin)– Analogs of pyrethrins from pyrethrum– Names end with “cyclopropanecarboxylate”

• Organophosphates (e.g., acephate)– Analogs from WWII German companies– Names end with “phosph(on)ate

• Carbamates (carbaryl)– Analogs of eserine– Names end with “carbamate”

Rice Insecticides: Classes• Neonicotinoids (e.g., thiomethoxam)– Act like nicotine– Names end in different ways…

• Diamides (e.g., Rynaxypyr®)– Completely novel mode of action– Names end with “carboxamide”

• Benzoylphenylureas (Dimilin®)

Target Sites• Organophosphates/carbamates

Group 1 (Acetylcholinesterase)

• Pyrethroids Group 3 (Sodium Channel)

• NeonicotinoidsGroup 4 (Nicotine receptor)

• Diamides- Group 28 (Ryanodine receptor)

Insecticide Safety

• Nerve poisons• Read and follow the label• Spray less toxic insecticides

Insecticide ToxicitiesInsecticide Chem Class (Group) Toxicity (LD5O)acephate organophosphate (1) 866malathion organophosphate (1) 1000methyl parathion organophosphate (1) 24carbaryl carbamate (1) 500- cyhalothrin pyrethroid (3) 80- cyhalothrin pyrethroid (3) 3200etofenprox pyrethroid (3) 42000zeta-cypermethrin pyrethroid (3) 90thiamethoxam neonicotinoid (4) 1563chlorantraniliprole diamide (28) >5000diflubenzuron benzoylurea (15) 4640

Contact Info

Dr. Jim OtteaJottea@lsu.edu225/578-1841