Geographic distribution, host range and perennation of Cotesiasesamiae and Cotesia flavipes Cameron in cultivated and natural habitats in Kenya

Abstract

Field surveys were carried out in four agroecological zones to assess the geographic distribution, host range and perennation of Cotesia sesamiae and Cotesia flavipes in cultivated and natural habitats in Kenya. The distribution of the two Cotesia species in different ecological regions was most affected by the suitability of the local stem borer species for parasitoid development, and temperature, as both species were found in localities dominated by their suitable host(s) where temperature favoured their occurrence. Fourteen years after its release, C. flavipes has maintained a high level of specificity to its target host Chilo partellus on maize and sorghum in cultivated habitats and on Sorghum arundinaceum in natural habitats. Cotesia flavipes appeared to be an appropriate biological control agent against C. partellus in eastern Africa, with minimal or no effects on non-target hosts in different habitats. Conversely, C. sesamiae lacked host specificity in different habitats, as its stem borers or host plants varied with both locality and habitat type. Perennation by both Cotesia species occurred mainly in cultivated habitats. Furthermore, natural habitats played a role in sustaining some individuals of C. flavipes during both rainy and dry seasons. These areas acted as refuges for C. flavipes, but not for C. sesamiae, because its hosts were scarce on natural host plants. The availability of these Cotesia species across seasons was mainly influenced by the presence of actively feeding stem borers on cereal plants during different seasons, as well as the duration of the dry season in different localities.