Developing ecological management strategies for virus diseases of tomato in Uganda

Tomato (Lycoperscum esculentum) is one of the priority crops considered to drive development and food security in Uganda. However, severe levels of viral diseases have been found to constrain productivity in Uganda: A survey found mean incidence of 60% for cucumber mosaic virus (CMV), 56% for tobacco mosaic virus (TMV), 39% for tomato mosaic virus (ToMV) in farmers’ fields. Kasese district was highest ranked (73%) with 85% as mixed infections. As such studies were implemented to i) establish the key channels of infection and devise ways to plug them, ii) promote management approaches that are applicable in smallholder farming systems. As part of efforts to address these objectives a longitudinal biological monitoring activity of tomato farms in Kasese districts was implemented in a drive to find the factors influencing the increasing occurrence of viruses on tomato in the district. Laboratory virus analyses of seed from farms and seed companies were also done. Other activities conducted as part of the project were intended to: i) assess effect of row covers, resistant germplasm on virus incidence and severity, and ii) determine effect of seed treatment and seedling protection on virus incidence and severity were conducted. Preliminary results indicate that cropping system and water management did not influence insect vector and virus disease occurrence on tomato but seed source significantly affected virus disease incidence. Also, infected seed and weeds are sources of inoculum for ToMV and CMV on tomato. From the field trials, row covers as a physical barrier for insect vectors, and resistant varieties have potential in reducing virus severity. The studies are ongoing to generate more conclusive results.