Evaluation of Fungicide Frequency and Rotation for Tomato Late Blight Management in Rain-Fed and Irrigated Conditions

Tomato late blight is among the major constraints that limit production in most tomato-growing areas. The field experiment was conducted in the Ambo Agricultural Research Center on-station and Toke Kutaye district in 2020/22 to evaluate fungicide application frequency and rotation and determine the economic cost of fungicide application for the management of late blight under rain-fed and irrigated conditions of tomato production. Cochoro, the tomato variety that is well adapted to the area, was used in the experiment. Five frequencies and rotations of fungicide application were arranged in an RCBD design with three replications. The result showed that the rotations of fungicide Victory 72 WP, Mancozeb 80% WP, and Ridomil Gold MZ 68 WP spray were found to have the lowest disease incidence (39.57%), percent severity index (25.02%), AUDPC (66.82% days), and highest marketable yield (29.75ton ha-1) in all locations as compared to the untreated plots that exhibited the highest percent disease incidence (100%), percent severity index (56.2%), and AUDPC (147.47%). Therefore, from the present study, the application of fungicides in the alternating order of Victory 72 WP to Mancozeb 80% WP to Ridomil Gold MZ 68 WP at a 7-day interval is recommended to reduce the late blight damage on tomato crops. In addition, the present finding has suggested that the planting of tomatoes should start during the mid-summer (late July or early August) to avoid the high-risk conditions for the late blight epidemic and reduce the frequency of fungicide sprays in the main rainy season.