Abstract:

The whitefly pest complex Bemisia tabaci (Gennadius. 1889) is one of the most devastating agricultural pests globally. Over the past two decades, increased abundance of B. tabaci populations throughout the cassava-growing regions of East and Central Africa has been reported. The recent outbreak of large B. tabaci populations intensifies its significance as a direct pest of cassava and also increases the prevalence of B. tabaci transmitted diseases. However, there are no practical B. tabaci management options available for smallholder farmers in the region. This is largely because previous research efforts focused on the development of virus disease resistant cassava genotypes with no special emphasis on the vector. The main aim of this study therefore was to understand the factors that influence B. tabaci population dynamics and fitness. To investigate the effect of cassava morphological traits, temperature, rainfall and relative humidity (RH) on the abundance of B. tabaci. five cassava genotypes (Alado alado. Njule Red, NAROCASS I. NASE 14 and NASE 3) with varying levels of resistance to B. tabaci vectored diseases and B. tabaci infestation were planted in three Ugandan agro-ecological zones in 2016 and 2017 in a randomized complete block design. Results have shown that B. tabaci Sub-Saharan Africa I (SSA 1) was the species on cassava in Uganda. The tallest genotype Alado alado supported the lowest number of B. tabaci adults. In areas with high B. tabaci prevalence, leaf area, leaf lobe and leaf lobe number exhibited significant positive effects (/?<0.001) on B. tabaci adult count across locations. Positive effects of relative humidity, and negative effects of temperature and rainfall, on B. tabaci adult and nymph counts were observed in 2016 and 2017. hence the low populations in the North Eastern Savanna grassland. Temperatures of 28-30 °C, rainfall of 30- 150 mm and RH of 55-70% and deployment of cassava genotypes of short stature with large leaf area and lobe width were significantly associated with increased B. tabaci populations.