Late blight on tomato has been confirmed on an organic vegetable farm in Henderson County, NC on 7 Aug 2023. A sample has been submitted for genotyping analysis to identify the strain and sensitivity to mefenoxam (the active ingredient in Ridomil).

Growers should monitor frequently for symptoms of late blight and begin applying systemic fungicides.

Tomatoes and potatoes 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 North Carolina for 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 on 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.