THE INSECTICIDAL ACTIVITY OF SOME ORGANOPHOSPHORUS COMPOUNDS AGAINST THE MIGRATORY LOCUST (LOCUSTA MIGRATORIA MIGRATORIOIDES REICHE & FAIRM.)

Although the insecticidal effectiveness of a compound is dependent on many factors, such as solubilities and detoxification, there appear to be distinct relationships between chemical structure and insecticidal activity. The insecticidal activity of paraoxon was significantly greater to the adult males of Locusta migratoria migratorioides than that of all other nitrophenyl-phosphorus compounds tested. This may be attributed to the direct action of the compound, involving no change from inactive to active form in vivo, and also to a better translocation of the compound from the point of application to the site of action. The toxicity of injected paraoxon was of the same order as that topically applied. Parathion, its isomers, and ethyl p-nitrophenyl phenyl phosphonothionate (EPN) were approximately equivalent, whereas malathion, although relatively low in toxicity, with an ED50 of 29 mu g./insect, was still a reasonably effective insecticide. Methyl, ethyl and isopropyl esters were effective in that order of toxicity. Substitution of other alkoxy or aryloxy groups resulted in loss of activity.