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Protect Cucurbit Crops Against Alternaria Leaf Blight

May 25, 2018
This agronomic image shows a cucumber field.

As the growing season heads into summer, it’s important to look out for potential crop diseases like Alternaria leaf blight. Also known as target leaf spot, this disease initially appears as small circular lesions on the upper leaf surface. Early lesions are yellow-brown with surrounding green halos and turn darker brown as they grow larger. Lesions often merge; leaves become cupped and die. The causal fungus penetrates plants either directly or through leaf pores and wounds. Severity of the disease increases with longer periods of leaf wetness, from 2 to 24 hours over temperatures ranging from 53 to 86 degrees Fahrenheit, and leads to reduced quality and yield.

According to the University of Maine, Alternaria leaf blight often survives through the winter months, infecting crop debris and serving as a primary source of infections, so proper fall management is crucial to preventing the fungus from re-infecting crops the following year.

There are several ways to get ahead of the disease:

  • Clean equipment at the end of each season.
  • Plow and bury excess crop debris.
  • Rotate crops.
  • Choose seed with tolerance to Alternaria leaf blight.
  • Manage nutrients in-season.
  • Apply fungicides.

If disease pressure persist, we suggest Aprovia® Top fungicide. A broad-spectrum product containing 2 fungicides, it has preventive and curative properties that provides excellent disease control of many leaf spots and powdery mildews.

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