Tomato late blight, caused by the oomycete Phytophthora infestans, was confirmed today (July 11, 2014) in a tomato sample from Henderson County, North Carolina and confirmed by the Plant Disease and Insect Clinic and the Quesada Lab at NCSU.
Late blight was confirmed in the Eastern part of the state a few weeks ago on a potato sample indicating that the pathogen has been in North Carolina for some time. The cool and wet weather recently experienced in the Western part of the state favored the late blight pathogen allowing it to cause infection in a tomato field. Symptoms were scattered in the field and about 10% of the plants were affected. Only foliar symptoms with no sporulation were observed and control measures are already being implemented by the affected grower.
It is important to remember that the late blight pathogen can travel long distances and that once the pathogen is found in a neighboring state or one county in North Carolina, it is likely already in several counties in the state. Outbreaks may not be seen due to lack of scouting or because environmental conditions are not favorable for disease even when pathogen inoculum is available. Therefore, it is critical that growers actively scout their fields, use preventive chemical control if possible, get accurate diagnostics if you suspect your crop has late blight, and implement control measures if you have an outbreak in your operation.
Tomato and potato can become significantly defoliated due to late blight within days if environmental conditions favor the pathogen. Immediate action to protect susceptible crops in NC from late blight is recommended, especially in the Western part of the state since wet and cool weather is conducive to disease. For more information about tomato late blight and how to control it see our tomato and potato late blight fact sheets, which list 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 and/or 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.