Blight (Late)

Late Blight disease is an aggressive fungus-like pathogen that thrives in cool, damp weather.


Late Blight is an aggressive disease that thrives in cool, damp weather. It primarily attacks tomatoes and potatoes. Its spores can travel for miles o the wind, infecting gardens and farms far away. 

Late blight can affect all plant parts and wipe out a healthy-looking plant in days. Young lesions are small and appear as dark, water-soaked spots. These spots will quickly enlarge under cool, wet conditions and a white mold will appear at the margins. Complete browing and shriveling of leaves and stems can occur within 14 days from the first symptoms. 

Infected fruit develops shiny, dark or olive-colored lesions which may cover large areas and cause soft rots. The spores can also wash down into the soil. The fungus produces a foul odor when infection is severe.

What To Do

  • Choose varieties that are resistant to late blight and choose seed potatoes that are certified "disease-free."
  • Remove and destroy any infected plants -- this disease needs living tissue to survive the winter. Rotate your vegetables, especially potatoes and tomatoes -- do not plant them in the same spot as last year.
  • Use soaker hoses to water plants to keep the leaves dry, or water in the day so leaves have time to dry. Give you plants lots of space. Maximizing airflow and light helps the plants resist disease.