Assessing yield and Efficiency Implications of Relying on Parasitoids for Control of Cereal Stemborers: The Case of Small-scale Maize Farmers in Kenya

Abstract

As part of a region-wide classical biological control (BC) program, the exotic larval parasitoid Cotesia flavipes was released in coastal Kenya in 1993 for the control of the invasive crambid cereal stemborers Chilo partellus. A 2-year survey of small-scale maize farmers covering the 2004 and 2005 maize production seasons was carried out in the area to compare yields and production efficiency (i.e. the capacity to obtained maximum yields with least cost input combination between farmers) who applied chemical pesticides and those who did not, thus knowingly or unknowingly relying on BC. The role of pest and parasitoid, habitat management techniques and soil fertility measures in influencing maize production was also investigated. The results revealed that average yields and technical efficiency of maize producers ranged from 1 to 1.2 ton/ha and 57.9–67.9%, respectively. Farmers could improve maize yields by up to 42% by improving production efficiency and optimal allocation of labor and use of inorganic fertilizers. Because of low average maize yields, the return to pest control was low. Farmers that had natural grassy habitats in the vicinity of maize fields, applied fertilizers or used chemical pesticides to control stemborers obtained equivalent yields. Future yield improvement efforts should promote biological control as part of a whole strategy package to improve maize yields.