A groundnut pest occurring in South Africa and widely reported as Aproaerema modicella (Deventer) has recently been identified by mtDNA CO1 analysis as Aproaerema simplexella (Walker), a strain native to Australia. Two experiments were conducted during 2011–2012 growing season at five sites in South Africa. The first experiment examined the preference of A. simplexella between groundnut, soya bean, lucerne, pigeon pea and lablab (common known host crops for A. modicella). The second experiment examined the effect of cypermethrin on the control of the pest on soya bean and groundnut at two sites. Among the host crops tested, soya bean was the most preferred by the pest followed by groundnut at all sites. The pest was also observed on pigeon pea at all sites, but the infestation was very low. Lucerne was observed as the less preferred host for this species. No infestation was observed on lablab bean across the sites. Spraying cypermethrin in groundnut and soya bean reduced infestation in both crops to very low levels. In the unsprayed plots, the high infestation levels significantly reduced crop yields.