Can Vetiver Grass be Used to Manage Insect Pests on Crops?

Abstract: Apart from its well known soil conservation properties, vetiver grass (Chrysopogon zizanioides (L.) Roberty; syn. Vetiveria zizanioides (L.) Nash) is reported to be repellent to many insect species. However, infestation of vetiver by pests of other crops has been recorded and concerns raised about vetiver grass being a refuge for insects pests. This paper addresses the benefits that vetiver may have in control of these pests. Chilo partellus, a lepidopterous stem borer of grasses is a pest that is often mentioned in vetiver literature. This insect is a serious pest of maize, rice and other grain crops in Asia and throughout East and Southern Africa where it can cause total crop failure. These observations prompted research on insect/vetiver grass interactions to determine the response of stem borer moths and larvae when they encounter Vetiveria zizanioides plants. The response of moths to vetiver grass, which could be either positive (attraction or arrestment) or negative (repulsion), would determine if vetiver grass could be used as trap crop for C. partellus in an integrated pest management system. Wild grasses such as Napier grass (Pennisetum purpureum) is successfully used in habitat management systems in East and Southern Africa. Studies were therefore conducted to determine preference of female moths for vetiver grass compared to maize and to determine the suitability of vetiver, Napier grass and maize for survival of stem borer larvae. Two-choice preference bioassays and larval survival experiments were conducted