Kiyoshi Kasamatsu

Quantitative structure-activity relationships of phenyl N-methylcarbamates against the smaller brown planthopper and its acetylcholinesterase

Abstract Insecticidal activity against smaller brown planthoppers and inhibitory activity against their acetylcholinesterase preparation were determined for a number of mono- and polysubstituted phenyl N-methylcarbamates. The indices of these activities were analyzed by means of free-energy-related substituent parameters and regression analysis. The mechanism of the inhibition reaction with the AChE preparation was shown to be quite similar but not entirely identical to those proposed earlier for reactions with bovine erythrocyte and fly-head enzyme preparations. The synergized insecticidal activity was found to closely correspond to the anti-AChE activity except for the o-isomers.

Stereoselectivity in Toxicity and Acetylcholinesterase Inhibition by the Optical Isomers of Papthion® and Papoxon

The synthesis of Papthion® and papoxon, optically active at the α-carbon of the α-ethoxycarbonylbenzyl moiety, was described. The optical isomers of papthion and papoxon exhibited a marked selectivity in the toxicity and anticholinesterase activity, respectively. d-Papthion was more toxic to mosquitoes, rice stem borers, diamond back moths and mice than the l-isomer. In contrast, l-papthion was more toxic to houseflies, and less toxic to mice and other insects than the d-isomer. Selectivity in toxicity appears to be directly related to the selective inhibition in vitro of acetylcholinesterase by the optical isomers of papoxon.

The Efficacy of Yellow Tape Formulation of Pyriproxyfen against the Sweet Potato Whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae)

A tape formulation of pyriproxyfen was prepared by coating the chemical onto yellow plastic film. We evaluated the transovarial ovicidal activity of the tape formulation against Bemisia tabaci and investigated the optimal application method and efficacy in a greenhouse. The tape formulation showed high ovicidal activity of over 80% mortality against B. tabaci for 4 days by a 30-second compulsory contact test. The formulation controlled the B. tabaci population on tomatoes by both “sideways spreading application” and “vertical hanging application”. “Sideways spreading application” was considered to be more practical, although there was no significant difference in efficacy between the two application methods. In a large-scale greenhouse trial of “sideways spreading application”, the tape formulation suppressed the B. tabaci population for 77 days. The results suggested that the tape formulation is promising as a tool for IPM because of its high efficacy and lower environmental impact.