Study of the Insecticidal Activity of Essential Oils from Erythrophleum guineense and Uvaria chamae on the Peanut Weevil Caryedon serratus Ol. (Coleoptera, Bruchidae)

Abstract

The objective of this research is to examine the toxicity of Erythrophleum guineense and Uvaria chamae essential oils on peanut weevils. Contact testing on peanut seeds was carried out on adult C. serratus for 144 hours at an ambient temperature of 30˚C in the laboratory. It has been shown that C. serratus weevils exhibited a toxic mortality rate of 5.65 ± 0.5%, at 0.2 µl, and of Erythrophleum guineense , at the same dose of 0.2 µl of Uvaria chamae exhibited a toxic mortality rate of 8.50 ± 0.55 a (like average lifespan in days). However, he was observed during this work, that an increase in doses resulted in a decrease in the toxic effect. This can be probably due either: insects’ adaptation or insect avoidance behavior at high doses of the extracts used. The essential oils cause 100% mortality when the highest dose is used, i.e. 0.8 μl after 2 days for Erythrophleum guineense and 0.8 μl after 4 days for Uvaria chamae . These substances have a protective effect on treated peanut seeds, as the weight losses observed are minimal at the highest doses and the germination capacity of the seeds remains intact. This study shows that the essential oils of Erythrophleum guineense and Uvaria chamae have insecticidal properties on adult C. serratus .