EFFECT OF MAIZE VARIETY AND STORAGE FORM ON THE DEVELOPMENT OF THE MAIZE WEEVIL, SITOPHILUS-ZEAMAIS MOTSCHULSKY

The effects of maize variety and storage form on development of the ma ize weevil, Sitophilus zeamais Motschulsky, were studied under artific ial infestation at 25 +/- 2-degrees-C and 70 +/- 5% r.h. in the labora tory. Three improved West African maize varieties, Abeleehi, EV8725-SR , Pop63-SR and the local variety, Volta Local, stored shelled and as c obs without husks (=unshelled) were used. Dissections of infested grai n were used to monitor insect development at regular intervals. Maize variety and storage form had a significant effect (P < 0.05) on the me an duration of most developmental stages. Across varieties, the mean t otal duration of larval stages (first to fourth) was 25.2 d on unshell ed grain vs 22.8 d on shelled grain. By day 30, 76% of third instar la rvae in shelled kernels had tunnelled to the germ and fed on the radic le and scutellum portions compared to 44% of the larvae in unshelled g rain. The pre-emerged adult spent 5.3 d longer in unshelled than in sh elled maize. The mean weights of the developing insect (across varieti es) were not significantly influenced by storage form, except for the first and third instar larvae, which gave higher mean weights on shell ed than unshelled grain. Both maize variety and storage form influence d the site of weevil emergence from the kernel.