Assessing the Impact of Varietal Resistance and Planting Dates on the Incidence of African Yam Bean Flower Thrips ( Megalurothrips sjostedti , Hochst. Ex. A. Rich) in Nigeria

摘要

African yam bean ( Sphenostylis stenocarpa , Hochst. Ex. A. Rich) is one of the underutilized leguminous crops in the tropics despite its nutritional potentials. One of the major reasons for the gross neglect of this crop in many parts of Africa is its low grain yield when compared to other grain legumes under monocrop. The infestation of the plant by flower thrips Megalurothrips sjostedti has been recorded as the major causes of low yield of the crop. M. sjostedti can cause yield losses of up to 100%. Following its current status as a minor crop, only very few researches have been undertaken in its production especially as it relates to insect control. Hence, in this study we assessed the effect of varietal resistance and three planting dates on the incidence of the thrips and crop yields in Nigeria during 2009/2010 farming seasons. The results indicated that all the varieties planted in May of each season were less infested by M. sjostedti and differed significantly from those planted in June and July of each season. Amongst the varieties assessed, TSs9 was the most resistance and differed significantly from the rest of the varieties. The results of the grain yield s showed that all the varieties performed better with higher grain yield s when planted in May than those planted later. The flowering and podding formation stages of AYB planted in July coincided with the peak population densities of M. sjostedti resulting in a considerable reduction in grain yield s. The highest grain yield s were recorded under a combination of early planting with resistant varieties. It could therefore be concluded that planting African yam bean earlier in the season has significant effect on M. sjostedti incidence and grain yield .