Enhancement of Diapause Development in a Stem Borer, Busseola fusca(Lep.:Noctuidae)by Dry Conditions

Abstract

A stem borer, Busseola fusca FULLER, a major insect pest on sorghum and maize in Africa, enters aestivation diapause at the final larval instar (USUA, 1970). Due to semi-arid conditions experienced in Western Kenya particularly around Mbita Point Field Station (MPFS), a monoharvest system is employed for sorghum culture. Under such conditions, B. fusca diapause lasts for 6 to 8 months (from June/July to February/March, dry season) in the dry stalks and stubbles of the host plants (UNNITHAN, 1987). Rainfall and artificial wetting apparently play an important role in the termination of larval diapause in several stem borers, Diatraea lineolata (KEVAN, 1944), Rupela albinella (VAN DINTHER, 1961) and Busseola fusca (SWAINE, 1957 ; SMITHERS, 1960 ; USUA, 1970). OKUDA (1988) reported that diapause larvae of B. fusca responded to sustained exposure to water only during the late stage of diapause to complete diapause. Here, effects of wet and dry conditions on the diapause development were examined in B. fusca. A relationship between diapause development and temperature was investigated.