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Extension > Garden > Commercial fruit and vegetable production > Plant diseases > Gray mold of tomatoes

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Gray mold of tomatoes

Angela Orshinsky and Michelle Grabowski

Importance

Although rare in Minnesota field grown tomatoes, gray mold thrives in the high humidity found in high tunnel tomato production. The fungal pathogen infects all above ground plant parts and can be highly destructive when environmental conditions favor disease.

Tomato fruit infected by gray mold

M. Grabowski, UMN Extension

Tomato fruit infected by gray mold

gray mold on tomato plant leaf

M. Grabowski, UMN Extension

Gray mold infection on a tomato leaf

Pathogen

The fungus Botrytis cinerea.

Host range

More than 200 plant genera, primarily broad leafed plants.

Identification

gray mold on tomato plant stems

M. Grabowski, UMN Extension

Gray mold infection on tomato stems

Signs and symptoms

Environment

white rings on tomato fruit

A. Orshinsky, UMN Extension

Small white rings on tomato fruit indicate failed gray mold infections

Biology and disease cycle

fluffy gray spores on tomato plant stems

M. Grabowski, UMN Extension

Fluffy gray spores of Botrytis cinerea, the gray mold pathogen

  • The fungus survives on numerous weed hosts, as a saprophyte on dead plant material, and as hard resting structures (sclerotia) in plant debris and soil
  • Spores are spread short and long distances by wind and rain, equipment, and workers
  • Infections begin on weak, dying or wounded plant tissue
  • Management

    Resistant varieties

    There are no tomato varieties with resistance to gray mold.

    Cultural control

    Chemical control

    Fungicides are available for control of gray mold on tomato; however, they should only be used once cultural practices have been implemented. Fungicide-resistant gray mold has been reported on many crops. Apply fungicide according to label instructions. Rotate fungicide groups and/or tank mix fungicides to avoid producing fungicide-resistant isolates.

    For a current list of fungicides for gray mold management see the Midwest Vegetable Production Guide.

    2016

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