Timing of releases of the parasitoid Habrobracon hebetor and numbers needed in augmentative biological control against the millet head miner Heliocheilus albipunctella

Abstract

Heliocheilus albipunctella de Joannis (Lepidoptera: Noctuidae) is one of the major insect pests of pearl millet in the Sahel. The native parasitoid, Habrobracon hebetor Say (Hymenoptera: Braconidae), is currently being promoted for augmentative biological control of the pest in the Sahel. The current study was carried out to identify the right time for releases of the parasitoid using either pearl millet growing stage, or pest occurrence as reference, and to determine the optimal number of parasitoids needed to cover a given area. Our results indicate that release of parasitoids at the panicle emergence stage or six weeks after first sight of eggs of H. albipunctella lead to highest parasitism of H. albipunctella larvae by H. hebetor. The dose of 800 parasitoids for a distance of 3 km radius was enough for controlling H. albipunctella. The implications of the results are discussed toward cost effective and practical recommendation adapted to the Sahelian conditions.