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WA Potatoes at Risk for Late Blight

May 31, 2019
This agronomic image shows late blight

Recent weather conditions in WA are increasing the probability of late blight infection in potatoes. Late blight thrives in rainy weather, and under such conditions, can damage potatoes quickly.

The first symptoms of the disease usually appear on lower leaves as small, light to dark green, circular or irregular-shaped water-soaked spots. White cottony mildew develops on and around these foliar lesions. Stems, petioles, and tubers are also susceptible to late blight.

Preventive planning is a key aspect of protecting potatoes from this yield-robbing disease. Washington State University offers some tips for early-season management:

  • Restrict irrigation until the crop is fully emerged.
  • Form good sized hills over developing tubers.
  • Eliminate culls and tuber refuse.
  • Eliminate volunteer potato plants, especially in fields that had late blight last year or the year before. Volunteers in these fields run a high risk of being infected.
  • Begin monitoring fields for late blight when plants touch within rows and continue monitoring until harvest.
  • Good communications among growers when late blight is present is essential for minimizing outbreaks in the region.  This disease spreads very quickly.

While a dry spell can interrupt the disease cycle, the infection will continue where it left off when damp weather returns. To help protect your crop, we recommend Revus Top® fungicide. The unique LOK + FLOTM action in Revus Top creates excellent contact activity by killing non-germinated spores on the plant surface and creating a barrier to further infection. It locks tightly to the waxy layer of the plant surface and flows steadily into the leaf tissue.

We also recommend Omega® fungicide, which attacks pathogens to provide disease control without encouraging resistance. Through multi-site modes of action, Omega offers strong protection against potato diseases like late blight and white mold.

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