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Comparison of two strategies for use of translaminar and contact fungicide in the control of potato late blight in the highland tropics of Ecuador

Kromann, P., Leon, D., Taipe, A., Andrade-Piedra, J.L., Forbes, G.A.
Crop protection 2008 v.27 no.7 pp. 1098-1104
Solanum tuberosum, potatoes, tropics, Phytophthora infestans, blight, fungal diseases of plants, disease control, cymoxanil, spraying, Ecuador
Strategies based on using the translaminar fungicide cymoxanil for control of potato late blight, caused by Phytophthora infestans, were compared in the highland tropics of Ecuador in three separate field experiments. In one strategy, a commercial formulation of cymoxanil mixed with mancozeb was sprayed sequentially three times early in the season; this was then followed by three sequential sprays of a commercial product containing mancozeb alone. For the other strategy, the same commercial products were alternated. For each strategy, a spray interval of 14d was used after the contact/translaminar mixture and 10d after sprays containing mancozeb alone. Both strategies were evaluated with a manually operated knapsack sprayer but with two levels of application quality. High quality was achieved with a constant pressure valve and a new nozzle, while for low quality, fungicide was applied without a valve and using a damaged nozzle. All treatment combinations gave adequate disease control and no consistent effect of application strategy or application quality could be measured on disease severity or yield. However, approximately twice the volume of fungicide was applied using poor quality equipment, regardless of the application strategy. Advantages and disadvantages of the strategies and their potential effects on fungicide resistance are discussed.