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Tomato Diseases | Powdery Mildew

Powdery Mildew



  • Symptoms differ for each species of powdery mildew.
  • A flat white moldy growth develops on the leaves.
  • Bright yellow or green irregular spots form on the upper sides of leaves from Leveillula taurica infection, and then sometimes develop into necrotic lesions surrounded by yellow circles.
  • A white mold develops on the undersides of the leaves from Leveillula taurica infection.
  • White or grey splotches form on the upper sides of leaves and progress to the stems from Oidium neolycopersici.
  • Rapid defoliation.

GH Powdery mildew 3 GH Powdery mildew 3-2 GH Powdery mildew


  • Fewer and smaller fruits.
  • Some fruits develop bright yellow spots.
  • Fruits are unaffected from Oidium neolycopersici infection.

Favorable Environmental Conditions

  • During the infection period, mild temperatures are more favorable.
  • High relative humidity is conducive to colonization of the plant.
  • Spore germination occurs from 50°F to 98°F, but the optimal temperature is about 70°F, and optimal relative humidity is 75 – 85%.

Often Confused With

powdery mildew

Scouting Notes

  • Look on the upper or undersides of leaves for yellow spots or white moldy growth.
  • Infected leaves should be removed and destroyed to prevent spread of powdery mildew.