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The solitary larval parasitoid Dinarmus basalis Rondani is a promising biological control of Callosobruchus maculatus F, a major insect pest of stored cowpeas in West Africa. Farmers traditionally introduce Hyptis suaveolens L. Poit. leaves in their granaries for protection of cowpea seeds against bruchid damage. However, effects of botanical treatment using this plant on host location behavior and reproduction of D. basalis remain unknown. Olfactometer studies showed that sublethal doses of volatiles emitted by the crushed leaves and the essential oils were repellent for naive females D. basalis, which had previously developed in the absence of H. suaveolens volatiles. These females were able to move in a three-dimensional device and to avoid the host patches associated with H. suaveolens volatiles. Their reproductive activity was consequently reduced in such patches. Females, which had been exposed to sublethal doses of H. suaveolens volatiles during their postembryonic development, were no lon...

Eupelmus vuilleti ( Crawford) is an ectoparasitoid of the seed-eating beetle Bruchidius atrolineatus (Pic), which is an important pest of stored cowpea, Vigna unguiculata Walp, seeds in West Africa. Herein, we investigated the dispersal abilities of females within columns of seeds to assess the potential of E. vuilleti as a biological control agent of bruchids in cowpea granaries. The influence of host presence together with the 2 abiotic factors light and gravity on parasitoid movement and parasitization efficiency were analyzed. E. vuilleti females were able to travel through large seed masses and parasitize hosts located at the end of the seed column opposed to their introduction zone. Parasitoid movement was stimulated by light. E. vuilleti females exhibited a negative geotropism. Females introduced at the bottom of the seed column dispersed more and parasitized more hosts than females introduced at the top. Host presence had some influence on the dispersal of the parasitoids within the seed column at a host density of 10 infested seeds for 16,000-18,000 uninfested seeds. This depended on female introduction zone because gravity was the major factor influencing dispersal. The possible applications of these results for biological control of bruchids in cowpea granaries are discussed.