Gray Leaf Spot

Gray leaf spot tomato disease, which in the U.S. occurs mainly in the southeastern states, exhibits small gray-brown spots on the underside of leaves. Eventually, leaves turn yellow and drop off.

Gray leaf spot doesn't directly affect fruit, but damage to foliage will reduce the quality and yield.

How to Identify Gray Leaf Spot

Gray Leaf Spot
Clemson University - USDA Cooperative Extension Slide Series,
Bugwood.org
Gray leaf spot
Clemson University - USDA Cooperative Extension Slide Series,
Bugwood.org
  • Small, brownish, circular specks on lower leaves.
  • Sometimes the spots grow together and kill large areas of the leaf.
  • Infected leaves die quickly and drop from the plant.
  • Infections are common in seedbeds or greenhouses when plants are young.

Causes

  • Caused by three different fungi of the genus Stemphylium.
  • Fungal spores are spread by the wind, or by splashing water.
  • The fungus survives for a long time on plant debris, weeds, and alternate hosts such as gladiolas.

Preventative Measures

  • Plant only high quality transplants, discarding any that show any sign of disease or stress.
  • Practice crop rotation on a three-year cycle with non-hosts.
  • Remove crop debris, volunteer tomato plants, and weeds that can host the disease.
  • Avoid wetting the leaves when possible by watering the base of the plant.
  • Plant resistant varieties (many are available).

Treatments

Natural remedies

  • No biological control strategies have been discovered yet.

Chemical treatments

  • Fungicides are very effective at controlling the disease.
  • Consult the technical references for product recommendations.

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Credits for technical content

  1. High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State University and Montana State University.



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