![]() EfficacyĬopper fungicides can be highly effective if applied prophylactically (before infection) and with complete coverage of all plant foliar surfaces, including the undersides of leaves where the pathogen typically sporulates. Farmers applying copper products should periodically soil test for copper to track trends in soil copper contents. Specific preventive and alternative measures would include destruction of cull piles, planting of disease resistant cultivars, roguing/destruction of diseased plants, irrigation management, and wide row spacing. Like any other synthetic pesticide used in organic agriculture, a farmer must first adopt all available alternative management practices and show that those practices are not sufficiently effective. They are regulated for use as disease management tools, with the restriction that they must be used in a manner that minimizes copper accumulation in the soil. This is estimated to result in between 10 and 40% higher yields compared to crops not protected by copper (in which the foliage has to be destroyed earlier)." (Leifert n.d.)Ĭopper fungicides are on the National Organic Program National List as synthetics. ![]() "Copper fungicides are estimated to extend the growing period (before the potato foliage has to be destroyed to prevent the spread of blight to the tubers and neighbouring fields) by between 2-4 weeks. As required by the certification process, farmers must use all available alternative practices to manage late blight, and describe these in the Organic System Plan, before deciding to apply a copper product. In regions of the world where late blight epidemics occur frequently, prophylactic copper applications are applied. Once late blight is initiated in a field, disease progress can occur very rapidly, killing all aboveground plant tissues within one or two weeks. However, in some regions, even when all best organic management strategies are adopted, if inoculum is blowing in from off-farm sources, potato cultivars are not resistant, and weather conditions are conducive to disease development, a late blight epidemic can occur. Organic farmers should practice best cultural management to manage this disease. Late blight (causal agent Phytophthora infestans) is a very difficult disease to control organically in regions where potatoes are grown on large acreage and rain occurs during the production period. New York State Agricultural Experiment Station. ![]() Cornell University College of Agriculture and Life Sciences. Resource guide for organic insect and disease management. ![]()
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