Oviposition behavior of Telenomus busseolae, Telenomus isis and Trichogramma bournieri on eggs of east African cereal stemborers

Abstract

The oviposition behavior of the scelionids Telenomus busseolae, Telenomus isis and the trichogrammatid Trichogramma bournieri was studied on eggs of lepidopteran cereal stemborers, which included the noctuid Busseola fusca, Sesamia calamistis, Sesamia nonagrioides, the crambid Chilo partellus, and the pyralid Eldana saccharina. Unlike Tr. bournieri, Telenomus spp. did not attack eggs of C. partellus and E. saccharina. Five distinct behavioral steps were observed, which included foraging, drumming with the antennae on the eggs, ovipositor insertion, egg marking, and walking and resting. Foraging, walking and resting were observed less frequently than the other behaviors. There was a clear hierarchy of behavioral steps leading to successful parasitism, which culminated in marking of eggs. Self-superparasitism (i.e., oviposition in an egg previously parasitized by the same female) was between 2.7–5.9% indicating that the three parasitoids were able to discern eggs that were already parasitized. Earlier studies on the bionomics and host finding ability together with the present findings on the oviposition behavior of the different parasitoids cannot explain differences in parasitism rates by the parasitoids in the field. It is suggested that the plant species and alternative hosts occurring in crop and natural habitats may play an important role in the population dynamics of the parasitoids and affect their importance in controlling key pests of maize.