Toxicity, Antifeedant and Growth Regulating Potential of Three Plant Extracts against the Desert Locust Schistocerca gregaria Forskal (Orthoptera: Acrididae)

Abstract

The main objective of this investigation was to assess the toxicity and growth regulating potential of Jatropha (Jatropha curcas L.), neem (Azadirachta indica A. Juss) and argel plant, (Solenostemma argel Hayne) against the desert locust, Schistocerca gregaria. The effect on fecundity, feeding behavior and egg hatchability was also studied. Argel of 5% concentration induced a significantly less (56%) antifeedant effect on desert locust nymphs compared with 79.62 and 78.92% for neem and Jatropha oils respectively. Significant mortality of 40.54 and 43.39% was recorded, 7 days after treatment, in insects treated with 10% concentration of neem and Jatropha oils respectively compared to 15.19% in the control. Argel resulted in the lowest mortality of 20.70% which was not significantly different from the control. There was a significant difference between treatments for the time it took surviving nymphs to moult to the next instar. Nymphs in the control group took significantly less time (11.3 days) to develop from the 5th instar to the 6th instar than those treated with neem and Jatropha oils where they took 17.5 and 16.5 days respectively. Argel was not significantly different from the control. Jatropha oil significantly reduced the fecundity of females developed from nymphs treated in the 3rd instar by 42.2% compared with 58.54% due to neem treatment. Argel caused no significant effect on fecundity of treated insects. Both Jatropha and neem oils resulted in 99.71% egg un-hatchability while argel had no significant effect. Of the three test products, only Jatropha and neem oil have shown growth regulating effect.