Efficiency of the chitin synthesis inhibitor lufenuron (cga-184699) on growth, development and morphogenesis of Schistocerca gregaria (orthoptera: acrididae).

Abstract

This paper deals with the objective of investigating the effects of Lufenuron (CGA-184699) on the growth, development and morphogenesis of the desert locust Schistocerca gregaria. Five concentration levels (1000, 500, 250, 125 and 62.5 ppm) were given through the fresh plant food to the newly moulted (4 th or 5 th ) instar or late-aged 5 th instar nymphs. All results were obtained 24 h after feeding. The growth of Lufenuron-treated nymphs was profoundly inhibited because their weight gain was drastically reduced. Such reducing action of Lufenuron was dose-dependent after treatment of 4 th instar nymphs but at the higher two concentration levels after treatment of newly moulted 5 th instar nymphs and at the higher three concentration levels after treatment of late-aged 5 th instar nymphs. After treatment of the last instar nymphs, early or late-aged, the developmental rate detrimentally regressed as a response to the prohibiting action of Lufenuron on the development. In contrast, such rate was promoted during significantly shortened duration after treatment of 4 th instar nymphs, may be to accelerate the development for avoiding additional adverse effects of Lufenuron. Lufenuron exhibited an inhibitory effect on the adult emergence after treatment of last instar nymphs, regardless of the timing of treatment. On the other hand, Lufenuron exerted no effect on this vital process after treatment of 4 th instar nymphs. Moreover, the present compound, at certain concentration levels, induced the adults to emerge in a rate more than that on control congeners. However, the emerged adults suffered a morphogenic action of Lufenuron because different deformed females were produced in increasing % as, at least, the higher three concentration levels were increased. In addition, the adult females spent only shortened longevity and then died. The shortening effect was dose-dependent after treatment of 4 th instar nymphs.