Overlap of insect growth regulator (cyromazine) concentration, treatment method and rearing temperature was studied on the southern cowpea weevil, Callosobruchus maculatus F. (Bruchidae: Coleoptera), under laboratory conditions. A concentration of 5% cyromazine and dipping treatment at 30°C showed a significant reduction in the reproductive rate by 0.5%. Moreover, increasing the cyromazine concentration led to a decrease in food consumption. Hence, treatment of cowpea seeds via dipping method provided more protection compared to spraying method. Also, the increase of cyromazine concentration led to an increase of generation's lifespan. The longest generation lifespan recorded was 33.33 days when treated with 5% cyromazine by dipping at 30°C. On the other hand, the shortest generation lifespan recorded was 25.33 days when treated with 1% cyromazine concentration by dipping at 30°C. This study showed that there is no effect of the overlap between studied factors, neither in the disparity of sex ratio nor in the disparity of males and females body weights.
Key words: IGR, Insect pest, reproductive rate, sex ratio, Trigard, cyromazine.
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