New Findings on Epidemiology and Management of Rice Yellow Mottle Virus Disease in the Southern Highlands of Tanzania

Three studies were conducted at Kyela district with the objective of adding knowledge on epidemiology and management of rice yellow mottle virus disease. The contribution of different weed management practices on disease transmission and effectiveness of Alvirus (C14H21O3N2), a botanical pesticide in disease control were each evaluated in a randomized complete block experimental design with three replications under two lowland and one upland rice cultures. Twenty elite rice genotypes were also evaluated for resistance to the virus and farmer acceptance in the same sites and on station at Kikusya upland ecology. The results indicated that the first hand weeding in seed broadcasted plots (farmer practice) led to 90% increase in disease incidence compared to 6% and 2% with hand hoe weeding in row planting and use of herbicides (Rilo 250EC 1.5l/ha and 2-4Damine4l/ha) respectively. Use of the latter resulted in 70 – 90% reduction of disease incidence and yield increase of 1.3 to 1.8t/ha or monetary gain of Tsh 614,000/= per hectare on average. Alongside capacity building, these practices were recommended to primary stakeholders. Alvirus achieved 100% disease control when used to soak seed 24 hours prior to planting followed by spraying 14 and 21 days after emergence or where only spraying was used. This new finding was useful for research purposes but warranted further studies to enhance applicability. Existence of differences in pathogen strains was evident between the locations where the genotypes were planted but nine appeared resistant across locations out of which 5 were new, highly acceptable and required promotion to farmers