A Search for Indigenous Parasitoids for the Control of the Larger Grain Borer, Prostephanus Truncatus (Horn) (Coleoptera: Bostrichidae)

Abstract

This study was conducted to identify indigenous parasitoids for the control of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera : Bostrichidae). A search was conducted at various market stores in the Greater Accra and Volta Regions to collect and identify parasitoids associated with stored product pests. Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae) and Dinarmus basalis (Rondani) (Hymenoptera: Pteromalidae) associated respectively with Sitophilus zeamais Motschulsky (Coleoptera:CurcuIionidae) and Callosobruchus maculatus (Fabricius) (Coleoptera : Bruchidae), were found to be the most abundant and most frequent. These two parasitoids were thus selected for investigation into their possible controlling effect on P truncatus. A. calandrae caused a significant suppression of 47.5% in S. zeamais population during a 16 weeks study period. A. calandrae also caused a significant suppression in P truncatus population to the tune of 43.8% within the same period of study. In this study, A. calandrae was found to prefer larger and older (3rd instar) P. truncates larvae for oviposition and development. All larger grain borer larval instars were however acceptable to A. calandrae for oviposition, with the 3rd instar being the most suitable for its development. D. basalis, on the other hand caused a profound 83.8% suppression in C. maculatus population at a mean parasitoid level of 26.7 in the treatment. D. basalis however did not attack P truncatus at all. A. calandrae therefore has the potential to contribute substantially to an integrated control of P truncatus in Ghana