In laboratory, growth chamber, micro-plot and small-plot field trials, 53 copper-freeudpreparations (CFPs) were examined for their potential to control potato late blightud(PLB) caused by Phytophthora infestans (PI). In-vitro, 43% of the CFP inhibited theudgermination of sporangia or the mycelial growth of the pathogen completely. In growthudchamber trials, 21% of them reduced PI foliar blight of tomato seedlings by at leastud80%. In contrast, in small-plot field trials with potatoes under practice like applications,udnone of the CFPs sufficiently controlled the disease. Even in micro-plot field trials withudapplications twice a week the efficacies did not exceed 60%. With in-vitro tests weudshowed that the reason for the insufficient performance of the CFPs was due to theirudlack of persistence and rainfastness. However, applications of copper fungicides withudlow rates according to the decision support system Bio-PhytoPRE resulted in a goodudcontrol of late blight. We recommend using this strategy until CFPs are developed forudpractise application.
展开▼
