Foraging behaviour of the egg parasitoid Uscana lariophaga: towards biological control of bruchid pests in stored cowpea in West Africa.
The egg parasitoid Uscana lariophaga is evaluated as a candidate for biological control of Callosobruchus maculatus on stored cowpeas in Africa. Aspects of the parasitoid searching behaviour were investigated. The parasitoid used odours from uninfested cowpea seeds and host eggs to locate host habitats and clusters. Host clusters with many eggs were more frequently located than clusters with few eggs. The parasitoid demonstrated a Holling Type II functional response, and the maximum number of hosts parasitized was determined by the ovarian egg load. Due to a strong arrestment response within host clusters, and area restricted searching behaviour after oviposition, U. lariophaga parasitized more eggs in host clusters with an even or clumped distribution than in those with a low density random distribution. This parasitoid was positively phototactic and negatively geotactic. It is concluded that, under optimal conditions, U. lariophaga could significantly reduce losses in stored cowpea due to C. maculatus.