Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Late blight caused by the fungus-like organism, Phytophthora infestans, was confirmed this week in DE, eastern shore VA, and the South Fork on Long Island, NY on potato. See the Potato Disease Advisory. Late blight was confirmed on tomato on Long Island, NY. Growers should be checking fields daily and maintaining preventative fungicide sprays. The weather conditions have been favorable the past few days but the hot weather forecasted for this weekend should help reduce the threat. The Delaware find was a small area at the end of a field next to woods and under power lines that obstructed the aerial application of fungicide applied to the whole field. Late blight specific fungicide has been applied.
For more information on controlling late blight on potato and tomato, see the 2011 Commercial Vegetable Recommendations. In addition to the information in the Commercial Veg Recs guide there is a very good table on fungicides for late blight on tomato and potato from Cornell University summarized by Dr Tom Zitter: http://vegetablemdonline.ppath.cornell.edu/NewsArticles/2011PotatoFungicide_emphasis_on_late%20blight.pdf
http://blogs.cce.cornell.edu/cvp/files/2011/06/2011-Tomato-Fungicide-Roster-and-Ratings-chart.pdf