The impact of the egg parasitoid Uscana lariophaga on Callosobruchus maculatus populations and the damage to cowpea in a traditional storage system

Abstract

In West Africa, Uscana lariophaga (Hymenoptera: Trichogrammatidae) parasitizes the eggs of Callosobruchus maculatus (Coleoptera: Bruchidae), an important pest of stored cowpea. The impact of the egg parasitoid on pest populations was evaluated in clay pots used in traditional storage in Niger. At the beginning of the storage period cowpeas were infested with different densities of larval instars and adults of C. maculatus and inoculated with one density of U. lariophaga. The higher the initial densities of C. maculatus, the better the egg parasitoid was able to establish itself and to control the population of C. maculatus, limiting the damage to cowpea. After three months of storage, the egg parasitoid significantly reduced the number of C. maculatus adults by 68 at the lowest and 86 percent at the highest initial density of the beetle; the percentage of damaged beans was reduced by 13 and 19% respectively.

Impact of the egg parasitoid Uscana lariophaga and the larval‐pupal parasitoid Dinarmus basalis on Callosobruchus maculatus populations and cowpea losses

“…The provision of honey to foraging parasitoids within cowpea storage structures still faces many practical problems, like easy access to the parasitoids, drying out of the honey, dust accumulation, and bruchids also feeding on it Wäckers et al, 1998). In our experiment U. lariophaga reduced the adult bruchid population considerably, but was less able to prevent damage to cowpea than in the experiment of van Huis et al (1998), although the initial densities of the bruchid and the parasitoid were about the same and the experiment was started at about the same time during the year. It is not clear why the effect of U. lariophaga in the reduction of damage to cowpea was less in this experiment.…”

“…The inoculation with many more bruchids in this experiment compared to the experiment of van Huis et al (1998) (400 bruchids versus 25, respectively) resulted in much higher egg densities and damaged seeds than in the control. The treatment with U. lariophaga gave less reduction of the bruchid population and damaged seeds, with the same rate of egg parasitism, compared to those observed by van Huis et al (1998). The treatment with D. basalis had much fewer seed losses than the control, and significantly reduced the bruchid population in terms of egg density (to 15% of the control).…”

“…Impact of the egg parasitoid on the bruchid population. The impact of the egg parasitoid on pest populations was earlier evaluated in an experiment in Niger similar to this one (van Huis et al, 1998). At the beginning of the storage period cowpeas were infested with different densities of C. maculatus and inoculated with one density of U. lariophaga.…”

“…In Burkina Faso, inoculation of D. basalis reduced C. maculatus populations by 85% compared to the control in experimental storage pots (Sanon et al, 1998). Introducing the egg parasitoid U. lariophaga alone in a traditional storage system significantly reduced the number of C. maculatus adults and more so at higher initial densities of the beetle (van Huis et al, 1998). Here, we studied the effect of the egg parasitoid U. lariophaga with and without the presence of the larval/pupal parasitoid D. basalis on populations of C. maculatus in granaries.…”

Biorational control methods for protection of stored grain legumes against bruchid beetles

“…Females of the wasps oviposit on the eggs, larvae, or pupae, 23,24], and controlled Acanthoscelides obtectus (Say) in Colombia [25]. Uscana lariophaga significantly reduced the numbers of C. maculatus adults, the rate of damaged beans, and seed weight loss in a traditional storage system in Niger for 3 months [26]. Tracking of the phenological relationship between A. calandrae and C. maculatus populations over 5 months suggested that A. calandrae reduced the C. maculatus populations [27].…”