Intercropping system: Potential for the control of bean flower thrips with masking of lemongrass and mexican marigold

Cowpea (Vigna unguiculata) is an important food and forage legume in Africa. The bean flower thrips (Megalurothrips sjostedti) is one of the major pests of cowpea in Sub-Saharan Africa, reducing crop yield. Chemical pesticides remain the main control strategy, even with their negative impact on human and environmental health. Intercropping with maize as a visual barrier is commonly used by the smallholder farmers to reduce pest populations on cowpea. The use of host and no-host volatiles is another alternative method to reduce thrips pest populations in IPM strategy. The objective of this study was to evaluate the effect of semiochemical interactions between cowpea and two repellent plants, Cymbopogon citratus and Tagetes minuta, on the behaviour of M. sjostedti. Initially, we evaluated the attractiveness of vegetative parts and flowers of four cowpea varieties (KK1, K80, M66 and eL) to male and female M. sjostedti using Y-tube olfactometer. With the exception of flower of cowpea variety KK1 which were attractive to female M. sjostedti, all the varieties induced repellence or neutral responses to both sexes of the pest. Combination of KK1 flower with either C. citratus cut leaves or T. minuta plant were less attractive than cowpea flower alone (KK1) for females. However, the inhibitory effect of C. citratus cut leaves disappeared after 24hours. Overall, these results highlight the potential of exploiting volatile compounds from repellent plants to reduce M. sjostedti infestation in cowpea cropping systems. (Resume d'auteur)