Late blight (Phytophthora infestans) is a water mold that can cause complete loss of potato and tomato crops in as little as 7 to 10 days after infection. So what can you do to stop the disease in 2013? Many growers’ crops survived the 2013 outbreak, but again at great expense. There were even a few farms using the stronger fungicides that reported finding LB, but as far as I know, the fungicides prevented extensive crop loss in all cases. In early September with more rain and cooler temperatures, conventional farms that had not switched to the stronger LB fungicides began reporting crop losses. By late July many more organic farms that did not use copper reported LB outbreaks, and by late August most organic farms had infected tomatoes and potatoes. I also recommended that all conventional farms begin preventative applications of the stronger, mobile, late blight-specific fungicides on their tomato and potato crops. It was recommended that these farmers destroy their infected field tomatoes and potatoes to help prevent further spread of the disease and to save high tunnel tomatoes at these sites from becoming infected. On July 13, two organic farms reported outbreaks of LB in both the eastern and western portions of the state. However, LB can spread when relative humidity nears 100%. Late blight spread is usually favored by cool temperatures and frequent precipitation, and July was the warmest month on record and completely dry through most of the state for the first three weeks. I recommended that all organic farms begin to apply preventative applications of copper, and all conventional farms start their early blight fungicide program to stop low levels of LB spores. We could only assume that there were plenty of gardens with infected tomato plants around Prospect. Since LB is not listed as a restricted pest in CT, the state has no authority to force a vendor to stop selling infected plants or to reveal where they purchased infected plants, so that a future epidemic might be avoided by cleaning up the problem at the source. The homeowner had purchased the plants from a local supermarket, but when contacted, the supermarket management did not provide the source of the infected plants. By Jude Boucher, Extension Educator, Commercial Vegetable Cropsĭuring the week of June 20, 2012, a Prospect, CT homeowner brought late blight (LB) infected tomato plants to the CT Ag Experiment Station diagnostic center.

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