Potato Late Blight Update #6 – June 1, 2017

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

Late blight was reported 5/29 near the North Carolina and Virginia border. Weather has been conducive for disease. A protective fungicide application for late blight protection is recommended. I have included Early Blight P values as well. A P value of 300 is the threshold for early blight fungicide application.

Greenrow – May 1, 2017

Date DSV Total DSV P Value
5/30-6/1 5 22 244
5/25-5/30 3 17 225
5/23-5/25 4 14 179
5/15-5/23 7 10 161
5/4-5/15 3 3 104
5/1-5/4 0 0 30


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: http://extension.udel.edu/ag/vegetable-fruit-resources/commercial-vegetable-production-recommendations/

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.

Print Friendly, PDF & Email