Vegetable Disease Updates – June 10, 2016

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland;

Late Blight Update
Late blight has been confirmed in both western Maryland, Garrett County on tomato and on the eastern shore in Accomack, VA on potato. The genotype of both outbreak strains is US23. This genotype is pathogenic on both tomato and potato. In our past experience, the strain has usually been sensitive to mefenoxam, which means Ridomil products are effective.

Cucurbit Downy Mildew Update
No downy mildew has been reported on any cucurbit crop in Maryland or Delaware. The closest outbreaks are on cucumber in Duplin County North Carolina. Downy mildew is present in Georgia on cantaloupes, acorn squash, yellow squash and cucumber. I don’t think the threat of downy mildew in Maryland is imminent, but growers should scout their cucurbits frequently for symptoms. Follow the progress of the epidemic online at

New Disease on Potato – Dickeya spp. Update
Earlier this year, Nathan Kleczewski at the University of Delaware, alerted all to a “new” bacterial disease of potatoes that is similar to, but more aggressive than black leg. He wrote an excellent article on the disease for the UD Weekly Crop Update on April 1 During the past two weeks, symptoms of black leg have shown up in potatoes in Delaware and Maryland. The potatoes were infected with the pathogen Dickeya.

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