Seasonal incidence of Plutella xylostella (Lepidoptera: Plutellidae) and its associated natural enemies in major crucifer growing areas of Kenya

Seasonal incidences of Plutella xylostella, diamondback moth (DBM) and its associated natural enemies were investigated in two agro-ecological zones of the major crucifer growing areas of Kenya in 2005 and 2006. DBM larvae and pupae were collected from the cabbage and kale crops grown in farmers’ fields and maintained in the laboratory for the emergence of parasitoid or DBM. Four larval, one larval-pupal and one pupal parasitoid species were recorded from DBM. The parasitoids recovered were Diadegma semiclausum, D. mollipla, Itoplectis spp., Cotesia plutellae, Apanteles spp., Oomyzus sokolowskii and Brachymeria species . D. semiclausum was the most dominant species throughout with highest parasitism rates of over 70% recorded in the highlands. C. plutellae , Apanteles and Brachymeria were recovered from mid-altitude between 800 and 125 m above sea level (ASL) in the semi arid areas. Generally, parasitism was significantly higher on B. oleracea var. capitata. D. semiclausum displaced the indigenous parasitoids from B. oleracea var. capitata.