Potato Late Blight Update #8: June 2, 2016

Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu

Green row: April 29th, 2016

Note- Late Blight was discovered in a commercial greenhouse in Western MD on 5/17/16. Race is US-23. Also note that symptoms of blackleg have been appearing in some varieties. Please contact me if you notice wilting, black stems, or other symptoms of blackleg and see the article titled “Dickeya dianthcola Update” by Kate Everts in this week’s WCU for more information.

  Townsend Camden Leipsic Kenton
Date DSV Total DSV DSV Total DSV DSV Total DSV DSV Total DSV
4/29-5/5 3 3 11 11 10 10 13 13
5/9-5/12 3 9 6 17 2 14 4 17
5/12-5/18 2 11 0 17 3 17 0 17
5/18-5/22 2 13 2 19 2 19 2 19
5/22-5/26 2 15 0 19 2 21 2 21
5/26-5/30 5 20 5 24 5 26 5 26
5/30-6/2 2 22 4 28 5 31 3 29

Notes: Season severity of 18 severity values indicates the need for the first fungicide application. An accumulated severity of 7 after fungicide application identifies the need for a subsequent fungicide application.

You can personalize your late blight forecasts for specific fields, sign up for email or text alerts, and enter in management information at http://blight.eas.cornell.edu/blight/. Real time fungicide application timing tables for locations within Delaware can be accessed at http://blight.eas.cornell.edu/blight/DE

See the 2016 Commercial Vegetable Production Recommendations-Delaware for recommended fungicides.

Any suspect samples can be sent to the Plant Diagnostic Clinic or dropped off at your local extension office. Dr. Nathan Kleczewski can also be contacted at nkleczew@udel.edu or 302-300-6962.

The website USABlight tracks tomato and potato late blight across the nation and can be found here: http://usablight.org/. Information on scouting, symptomology, and management can also be found on this website.

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