Vegetable disease update, 8/19/15

Cucurbit downy mildew. Yesterday, the UNH Plant Diagnostic Lab confirmed the presence of downy mildew on a cucumber sample from Rockingham County. Cucumber and melon are susceptible to all pathotypes of this disease, while squash and melon cultivars vary in their reactions. Good photos of symptoms are found here, and management tactics and fungicide recommendations are found in the New England Vegetable Management guide, here. Fungicides vary in their effectiveness in combatting this disease; Meg McGrath from Cornell has published a very good description of the activities of different materials here. ***NOTE*** If you suspect that you have cucurbit downy mildew, please send it to Cheryl Smith in the Plant Diagnostic Lab for confirmation (there will be no charge for the sample), so we can track its’ movement.

Late blight. Late blight has been in Northern VT for several weeks, and many cases have been reported in central ME. Today it was reported in Franklin County, MA. It is all around us, so be vigilant for this disease. See this helpful page for a refresher on symptoms of late blight. If you are not sure whether something you see is late blight, please e-mail photos to the UNH Cooperative Extension Education CenterCheryl Smith, or Becky Sideman. The UNH Plant Diagnostic Lab will also confirm late blight samples at no charge.

Humid and overcast weather, especially if it rains over the next few days, is ideal for the spread of both of these diseases – please scout your crops and apply preventative fungicides if you plan to do so.

– The UNHCE Vegetable & Fruit Team

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