Late Blight on Tomato Confirmed in Haywood County, NC (Aug 26, 2019)

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Late blight on tomato was confirmed in Haywood County on August 26, 2019, and confirmed by microscopic observation of the sporangia under the compound microscope. Samples will be sent to Cornell for genotyping and sensitivity to mefanoxam. An update will follow.

UPDATE (Sept. 3, 2019): This strain is US-23 which is known to be sensitive to mefenoxam, the active ingredient in Ridomil.

Late blight symptoms on tomato leaf

Late blight symptoms on tomato leaf

Growers should monitor frequently for symptoms of late blight and begin applying systemic fungicides. Tomato and potato are extremely susceptible to this disease and can be significantly defoliated within days if environmental conditions are conducive. Heavy morning dews and cool, wet weather favor this disease. Active scouting and preventive fungicide applications to protect tomato crops in NC from late blight is recommended.

For more information about late blight and how to manage it, see the tomato 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 tomatoes, please contact your local Extension Agent and send photos and/or physical samples to the NC State University Plant Disease and Insect Clinic. If late blight is confirmed in your samples by an expert, please submit a report to the USAblight website to alert other growers. The USAblight website also contains information about disease identification and control.