Lecture 10 Outline
February 19, 2007
Insecticides
Donald E. Mullins
Department of Entomology
Reading assignment
= Ware & Whitacre: Chapters 4 and 17
(A PDF of the Powerpoint lecture is available..
Click
here)
III. Organochlorines: (continued from Lecture
9)
- DDT (continued from Lecture 9)
- mammalian toxicity
- AOT = 87 to 250 mg/kg in rats
- volatility = 0.025 mPa @ 20 degrees Celsus
- Hexachlorocyclohexane = Benzene Hexachloride
- discovery
- lindane = gamma isomer
- mammalian toxicity = 76 mg/kg
- volatility = 5.6 mPa @ 20 degrees Celsus
- solubility = 7.3 mg/kg
- Cyclodienes: General
- eight compounds 1945 to 1958
- stable and persistent
- endomethylene bridge
- epoxidation = activation reaction
- resistance in soil insects
- very important termiticide (chlordane)
- mode of action
- metabolism
- slow
- dechlorination + dehydrohydration of epoxide
- excretion
- mammalian toxicity
- chlordane AOT = 365-590 mg/kg
- endrin AOT = 7-15 mg/kg
- volatility: @ 20 degrees Celsus ...comparisons
- DDT = 0.025 mPa (1x)
- chlordane = 1.3 mPa (52x)
- lindane = 5.6 mPa (224x)
-
Polychloroterpenes:
- Toxaphene
- discovery
- chlorinated camphene
- 177 to 700 derivatives
- toxaphene A = 3% technical
- cotton insecticide
- persistent in soils
- does not biomagnify
- neurotoxin
- metabolized by mammals fairly easily
IV. Organophosphates:
- Discovery and historical perspective
- Properties
- broad spectrum
- easily hydrolzable
- slightly soluble in water
- readily soluble in organic solvents
- some hve good acaracidal properties
- some are effective as plant & animal systemics
- choline esterase inhibitors (synaptic poisons)
- Nomenclature
- Aliphatic derivatives-
- TEPP
- AOT = 0.2 mg/kg
- very unstable
- Malathion:
- most heavily used
- control of theMediterranean fruit fly
- AOT = 885 - 1350 mg/kg
- activation: malathion to malaoxon
- Phenyl derivatives--
- Ethyl parathion
- 1992 cancelled for most uses
- AOT = 3 mg/kg
- activation: = ethyl paraoxon
- Methyl parathion
- broader spectrum
- shorter residual life
- AOT = 9 mg/kg
- microencapsulated: AOT = 270 mg/kg
- activation: = methyl paraoxon
- Heterocyclic Derivatives--
- Diazinon:
- Chlorpyrifos:
- Azinphosmethyl (Guthion):
- agricultural uses under review (FQPA)
- AOT = 13 mg/kg
- ADT = 250 mg/kg
- Toxicity comparisons--
- Range of toxicities:
- Malathion = 1375 mg/kg
- Phorate (Thimet) = 1.6 mg/kg
- (TEPP) = 0.2 mg/kg
