Late blight on tomato has been confirmed in Henderson County as of Friday, August 21.

UPDATED 9/1: Genotyping results suggest that the lineage found in Henderson county is unique to the US. This means that we do not know how this strain will respond to fungicides, if it may overcome some host resistance, and how easily it spreads, reproduces, and survives the winter. Because of this, we are looking to collect samples throughout the region. If you have late blight, call (540) 577-8607 or email myself (ereeves2@ncsu.edu).

Original advice still applies based on our knowledge of how previous strains have behaved. That being said, if you see control failure with fungicide use, please let us know. This disease can spread rapidly and over long distances under favorable conditions (high humidity, frequent rainfall, moderate temperatures), so growers in the western region should begin preventative sprays on susceptible varieties of tomato. Spray programs should include a rotation of 2 or 3 active ingredients alternated with chlorothalonil. If you're in harvest, Orondis Opti, Orondis Ultra, Presidio, and Ranman all have PHIs of 0 to 2 days. Revus Top is another product with a PHI of 1 day that will also protect against early blight. Of these, the Orondis products have shown excellent efficacy in trials in the southeast. Revus Top and Zampro have performed well. Ridomil Gold Bravo also performed excellently but has a PHI of 5 days.

Symptoms of late blight on leaves include grayish-brown, irregularly shaped lesions that expand rapidly. The edges of the lesion appear water-soaked after rainfall or morning dew, and white sporulation is often evident on the edges of the lesion. Symptoms on fruit appear as dark brown, expanding lesions that are firm.

For more information about this disease, including varieties that are resistant and fungicide recommendations, see this disease factsheet.