Reproduction of the parasitoids Anisopteromalus calandrae (Howard) and Lariophagus distinguendus (Förster) on arenas containing a mixed population of the coleopteran pests Sitophilus oryzae and Rhyzopertha dominica

Abstract

In this article, we assessed the reproduction rates of the generalist pteromalid parasitoids Anisopteromalus calandrae and Lariophagus distinguendus on the coleopteran pest species, Sitophilus oryzae and Rhyzopertha dominica, when these hosts were offered together under environmental conditions reproducing spring or early summer. These species had proved to be the most suitable hosts in terms of parasitoid progeny production for both parasitoid species in no choice experiments in previous studies. Trials with A. calandrae and L. distinguendus had lower pest emergence in the parasitoid treatment when compared to the control for S. oryzae. However, for R. dominica, there was no difference between treatments for either parasitoid species. Pest reduction levels reached by the two parasitoids were caused by parasitism effects together with other parasitoid-induced mortality causes, which included host feeding and unsuccessful parasitism. The most preferred host under the conditions tested for both parasitoid species was S. oryzae. The parasitoid L.distinguendus decreased grain loss significantly more than A. calandrae thanks to a greater reduction of pest population. Product loss in terms of reduction of the medium (brown rice) weight was always higher in the control treatments.