P. Kantwatsa, E. Adipala, J.J. Hakiza and H.M. Kidanemariam
Late blight (LB), caused by Phytopthora infestans (Mont.) de Bary, is the most damaging disease of potato in the highlands of Uganda. Two types of studied were conducted at Kalengyere Research Station the objective of identifying the most effective and sustainable disease management options for development of an integrated disease management (IDM) package for LB in Uganda. The first study evaluated the effects of fungicide, planting date and variety on LB occurrence and severity. In the second experiment, the efficacy of 2 fungicides: Dithane M-45, Ridomil was evaluated singly and in combination to determine a suitable spray interval for controlling LB. Early planting of potatoes resulted in the highest disease severity levels in both season and late planting had the lowest disease severity levels. Higher yields resulted from early plantings of the second season, while late ones, had low yields. Yield gain due to fungicide sprays against LB, in the first and second seasons were in the range of 2-26.8 % and 12-75 %, respectively. In the study to establish the optimum spray interval for controlling LB, a spray interval of 7 days with Ridomil, and Ridomil first followed by Dithane M-45 was highly effective and resulted in high yields.