Late Blight Found in Buncombe County, NC – August 25, 2016

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Tomato late blight, caused by the oomycete Phytophthora infestans, was reported to NCSU Extension Agent on August 25, 2016 from a conventional tomato field in Buncombe County, NC. Symptoms were first observed on the previous day. Samples are being submitted for genotyping to determine the isolate and senstivity to mefanoxam (Ridomil) and results will be posted on this alert. The sample submitted was identified as US-23 lineage which is reported to be sensitive to mefanoxam (Ridomil), is the predominant genotype in the eastern US, and is known to attack tomato and potato crops (Updated 9/2/2016).

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.

Late blight (Phytophthora infestans) on tomato leaf

Late blight (Phytophthora infestans) on tomato leaf

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 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.