Scout Potatoes for Late Blight Due to Recent Reports

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Late blight, caused by the oomycete Phytophthora infestans, was reported this week from a tomato sample from Maryland. Further analysis of the sample by USAblight has determined that it belongs to P. infestans US-23, a strain that can infect potato and tomato.

Potato and tomato are susceptible to this disease, and can be significantly defoliated within days if environmental conditions favor the pathogen. Active scouting of potato fields for late blight is recommended. While there are no nearby sources of inoculum, the pathogen is airborne and timely detection of any infected plants is key for successful disease control. Preventive fungicide applications to protect potato crops in NC from late blight should be initiated if infected plants are detected, and if the weather will be wet and cool, which is conducive to disease.

For more information about potato late blight and how to control it see our potato late blight fact sheet, which lists effective products against late blight. Control recommendations are also available in the USAblight website, where you can register to receive text and/or email alerts when new disease outbreaks are reported.

If you think you have late blight in your potatoes please contact your local Extension Agent and send photos and/or physical samples to the Plant Disease and Insect Clinic. If late blight is confirmed in your samples by an expert, please send a report at the USAblight website to alert other growers. The USAblight website also contains information about disease identification and control.

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