Submitted to: Crop Protection Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/23/2004
Publication Date: 11/1/2004
Citation: Namanda, S., Olanya, O.M., Adipala, E., Hakiza, J.J. 2004. Fungicide application and host resistance for potato late blight management: benefits assessment from on-farm studies in s.w. uganda. Crop Protection Journal. 23: 1075-1083 Interpretive Summary: Late blight of potato is a significant constraint to potato production in tropical and temperate regions of the world. Fungicide management in combination with host-resistance is among the options readily available to growers for late blight management. The cost effectiveness of fungicide application regimes when used on potato varieties with different levels of late blight resistance was evaluated in replicated on-farm experiments. The fungicide application intervals were: weekly, 14 day intervals, IPM, no spray control and growers' practice. Based on late blight disease monitoring, the application of Dithane M-45 was significantly reduced when a moderately resistant variety was used. High tuber yield and significant economic gains as measured by the marginal rates of return and net benefits were obtained in IPM treatments compared to other fungicide application intervals.
Technical Abstract: Late blight caused by Phytophthora infestans, is one of the most significant constraints to potato production in Uganda and other regions of the world. Fungicide management and host resistance are among the most efficient control options available to potato growers in low-input farming systems. Field trials were conducted in 1999 and 2000 in Southwestern Uganda to evaluate the cost effectiveness of fungicide application regimes on potato varieties with various levels of resistance. A factorial experiment consisting of five fungicide application intervals (weekly, fortnightly, IPM, no spray and farmers' practice), and five potato varieties was established during 1999 and 2000. Late blight infection was prevalent in both years, and significant levels of disease was detected (P<.05). Application of fungicides considerably reduced late blight progress with a corresponding increase in tuber yield. The Results of the study showed that based on monitoring of disease occurrence and weather variables, two applications of the contact fungicide Dithane M45 on a moderately resistant variety was the most economical. Similarly, marginal rates of return and net benefits were significantly affected by fungicide applications. In the IPM treatment, late blight disease monitoring or scouting prior to first fungicide applications resulted in significant economic gains compared to scheduled applications (weekly / biweekly) or no application (control) treatments.