Caged colonies (approximately 200 individuals, nymphs and adults) of flower bud thrips (Megalurothrips sjostedti Tryb.) were given 48 h acquisition feed on cow pea (yellow) mosaic virus (CY M V)-infected plants of cow pea (Vigna unguiculata (L.) Walp.) after the presence of virus in the reproductive structures had been confirmed by serology (Elisa technique). Thrips inoculation of test plants, involving the serial transfer of thrips for ten days at 48 h intervals, in no case led to the development of virus symptoms though, in the ELISA tests, a positive reaction was obtained with one plant when pods were assayed. This suggests that flower bud thrips are unlikely to be significant vectors of CYMV in the field, especially since populations of M. sjostedti do not build up until cowpea plant begin reproductive growth when virus infection may have little effect on cowpea seed yield.