Pesticides I

1

• Pesticides I
• History of development
• Trends in use
• Ranges of toxicity

• Overview of Modes of Action
• Major Classes of Insecticides
• Chlorinated hydrocarbons
• Organophosphates
• Carbamates
• Pyrethroids

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Natural Products
Tobacco
Metals
Copper sulfate
Lead arsenate
Chlorinated hydrocarbons
DDT
Parathion
Organo-phosphates
Malathion
Carbamates
Sevin
Permethrin
Pyrethroids
Bt
Microbials
Juvenoids
IGRs
3
Herbicides
Trends in pesticide usage
Corn
Soybeans
Overall
P.I.K.
Wheat cotton
Herbicides
Insecticides
Cotton
IPM
Insecticides
Corn
Fungicides
Soybeans
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Relative Toxicities
Chlor. Hydrocarbons Carbamates Pyrethroids
DDT (oral200)
LD50 (mg/Kg)
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Relative Toxicities- Organophosphates
LD50 (mg/Kg)
6
General Modes of Action
Synapse
Axon
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Chlorinated hydrocarbons (organochlorines)
DDT
DDT history, persistent, water insoluble, cheap,
abuse
8
Mode of Action of DDT
Repetitive discharge of action potentials
Prolonged action potential
Molecular wedge hypothesis
9
Target sites of other chlor. hydrocarbons
similar acting toxins
Prop Na channels open
Block Cl- channels on GABA receptors
prevents calming effect
10
DDT for mosquito control
Malaria in Sri Lanka
Cases
DDT
Resistance
11
DDT and biomag-nification
DDT and breast cancer
12
World-wide use of chlorinated hydrocarbons
13
Other popular chlorinated hydrocarbons
DDE
Methoxychlor
Dieldrin
Chlordane, Heptachlor
BHC, Lindane, Kelthane, PCBs