EGG Parasitoids for Augmentative Biological Control of Lepidopteran Vegetable Pests in Africa: Research Status and Needs

Among the important constraints to vegetable production in Africa are the lepidopteran pests, in particular Helicoverpa armigera (Hb.) and Plutella xylostella (L.) which cause direct yield loss as well as cosmetic damage. Egg parasitoids, especially Trichogramma spp., shown promise as biocontrol agents against both species in previous studies. In Africa, surveys have so far recorded 18 species of Trichogramma, eight of Trichogrammatoidea and seven of Telenomus besides one species each of Baryscopus and Oencyrtus. For effective utilisation of egg parasitoids in vegetable ecosystems in Africa, the experience gained elsewhere should be suitably utilised, and complementary research undertaken. This paper examines the scope for use of egg parasitoids in Africa, focusing on five research areas. Firstly, surveys should be undertaken to collect, characterise, and catalogue the different species and strains of egg parasitoids occurring in the region. Secondly, the pest status of target Lepidoptera and the potential demand for use of egg parasitoids in the major ecologies should be assessed. Thirdly, the local and/or exotic species/strains with good potential to control H. armigera and P. xylostella need to be identified, and fourthly, analyses aimed at selecting appropriate mass production and delivery systems for Trichogramma use in major vegetable crops should be undertaken. Finally, optimisation of inundative release strategies should be researched on. The scope for research collaboration within Africa and internationally is discussed.