Kinetic investigation into the interaction of chlorpyrifos and thiodicarb with acetylcholinesterase activity from some harmful and beneficial insects

Acetylcholinesterase [AChE] is the target site of organophosphate and carbamate insecticides and is responsible for the intoxication resulting in death of insects. Partially characterization of AChE and its interaction with organophosphate and carbamate has been studies. The inhibition of AChE by two insecticides; chlorpyrifos and thiodicarb was investigated in the head homogenates of two cotton leafworm Spodoptera littoralis strains; laboratory and field srain; cut worm, Agrotis ipsilon and honey bee Apis millefra. The results obtained revealed that the AChE from different insects is identical in us properties. Highly activity of AChE was detected in the head homogenate of adult insect of honey bee. The lowest I[50] value micro M [the highest inhibition potency] was obtained with thiodicarb against all the tested insect species. The lowest inhibition was obtained with thiodicarb and chlorpyrifos against field strain of S littoralis compared to laboratory strain. According to Dixon plots, the inhibition pattern of either chlorpyrifos or thiodicarb was a noncompetitive type

Feeding deterrent and growth inhibitory properties of larval frass against spodoptera littoralis [boisd.]

The research has been conducted to evaluate the activity of the frass extracts of Spodoptera littoralis [Boisd.] against its larvae. Five solvents differ in their polarity namely petroleum ether; chloroform; acetone; ethanol and water were used to extract the frass material The following points were studied: [a] evaluation the toxicity of different extracts against S. littoralis larvae [b] effect of frass extracts on the development of S. littoralis larvae [c] evaluation of the antifeedant activity of frass extracts against 4th instar larvae of S littoralis. Results showed that the 10% concentration of frass exhibited strong antifeedant activity. On the other hand ethanol and water extracts [highly polar] caused the highest mortality percentage whilst petroleum ether and chloroform [non-polar] caused the highest percentage of antifeedant activity, respectively. The type and concentration of extracts by water, ethanol, chloroform and acetone affected the sex ratio and development of S. littoralis. In general, the biological activity of frass extracts was solvent type-and concentration-dependent