Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
Unfortunately late blight has continued to appear in tomatoes over the past week. Locally, a second high tunnel outbreak in St. Mary’s County, MD was confirmed last week. This is the second confirmation in Maryland and is about one mile from the first outbreak. So far no other outbreaks in Maryland and none in Delaware have been reported. In other states, an outbreak in a Pennsylvania greenhouse was confirmed on May 17 (that crop was destroyed).
In northern Kentucky on May 27, infected transplants were found in one home garden and several box stores. These transplants had been grown outside of Kentucky and shipped to the box stores for sale. The stores involved are national chains. The transplants, which are destined for home gardens, pose a huge threat because they would provide widespread dispersal of inoculum. We hope to avoid a recurrence of this scenario, which caused widespread commercial losses in 2009. Everyone is encouraged to be vigilant. If late blight is suspected – please contact your extension educator.
Again I am recommending that commercial tomato growers apply a protectant fungicide such as chlorothalonil (Bravo), Gavel, or mancozeb. Scout aggressively for symptoms and switch to more targeted translaminar products when late blight is found.