Controlling bruchid pests of stored cowpea seeds with dried leaves of Artemisia annua and two other common botanicals

Abstract

Insecticidal activities of dried Artemisia annua L. leaves were evaluated against bruchid (Callosobruchus maculatus F.) pests in comparison with those of Azadirachta indica, Ocimum gratissimum and a conventional grain storage insecticide, Actellic® 2% dust. Each treatment was added to a mixture of 250 g cowpea seeds and 25 adult bruchids and laid out in a completely randomized design with four replicates. Irrespective of the concentration tested, all three plant materials significantly (P < 0.05) increased mortality rate of adult insects earlier than the control. Higher concentrations of the botanical pesticides equally resulted in an increased reduction in the number of surviving bruchids and reduction to seed damage through a lower number of eggs laid and weevil perforation index (WPI) after 90 days. Comparatively, A. annua was more effective than the other plant materials at all levels evaluated though it was not as effective as Actellic 2% dust. Moreover, differences amongst the efficiency rates and interactions between A. annua and A. indica in three treatment combinations produced a significant (P < 0.05) effect on two of the parameters evaluated. Taken together, all plant materials evaluated here were seen to have significant insecticidal properties and could therefore, be used as environmentally friendly products for controlling bruchid pests during storage of cowpeas with no adverse effects on eventual mammalian consumers as observed during an animal feeding trial in this study.

Key words: Actellic 2% dust, botanical pesticides, Callosobruchus maculatus, Vigna unguiculata, weevil perforation index.