Temporal and spatial dynamics of Bemisia tabaci populations and cassava viral diseases on selected whitefly resistant cassava genotypes in Uganda

Abstract

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a pest that causes widespread damage on cassava (Manihot esculanta Crantz), a staple food crop for millions of households in sub-Saharan Africa. Bemisia tabaci also acts as a vector responsible for spreading plant viruses that cause two of the most economically damaging diseases in cassava; namely cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The objective of this study was to determine the population dynamics of B. tabaci on whitefly resistant cassava genotypes in different agro-ecologies in Uganda. Data were collected once a month, for six months on adult whitefly populations, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) incidence and symptom severity. The results obtained indicated that cropping season (2015 and 2016), agro-ecology, cassava age and genotypes strongly (P<0.001) influenced the population of adult whitefly. Moderate (47.44% ± 0.7821) and high (72.04% ± 0.6916) overall means incidences of CBSD recorded across agro-ecologies on the whitefly resistant genotypes in 2015 and 2016 trials, respectively, were likely due to use of cutting-infected planting materials that were not detected through visual inspection at trial establishment. The analysis further revealed that the interaction effect of genotype, agro-ecology and crop age (months after planting: MAP) had a highly significant influence (P< 0.001) on whitefly abundance and high significant effect (P<0.05) on CMD incidence and severity. The CMD and CBSD incidence as well as symptom severity increased with crop age from 3 months after planting across agro-ecologies. The study demonstrates that whitefly population dynamics and viral disease incidence are influenced by cassava genotypes, agro-ecological differences and crop age (MAP). Information generated could be used to guide the development of appropriate area-specific control strategies to mitigate the effect of whitefly and whitefly-transmitted viral diseases in cassava.