Bacterial wilt

Quick facts

  • Bacterial wilt can cause severe losses in cucumbers and muskmelons.
  • Leaves eventually yellow and brown at the margins, completely wither and die.
  • Wilt progresses down the vine until the entire vine wilts or dies.
  • The bacteria overwinter in the gut of striped and spotted cucumber beetles. It cannot overwinter in Minnesota in plant debris.
  • Managing cucumber beetles provides the most effective control of bacterial wilt.
  • Pesticides will not help in managing a cucurbit plant infected with this bacterial disease.
Plant infected by bacterial wilt; collapsed and wilted vines, leaves and flowers
H.F. Schwartz, Colorado State University, Bugwood.org

The bacterium Erwinia tracheiphila causes bacterial wilt. This pathogen can cause severe losses in cucumbers and muskmelons. It does not affect squash and pumpkins as much. Bacterial wilt does not affect watermelon. Bacterial wilt does not occur every year in Minnesota.

Vine infected by bacterial wilt
Vine infected by bacterial wilt; G. Holmes, CA Poly Tech State University, Bugwood.org

Identifying bacterial wilt symptoms

  • Leaves first appear dull green, wilt during the day and recover at night.
  • Leaves eventually yellow and brown at the margins, completely wither and die.
  • Wilt progression varies by crop.
    • Cucumbers and melons wilt and die rapidly.
    • Pumpkins take up to two weeks to wilt completely
    • Summer squash may continue to produce for several weeks even when infected.
  • Wilt progresses down the vine until the entire vine wilts or dies.
  • Striped or spotted cucumber beetles will be present in the garden.
  • If infected vines are cut close to the crown of the plant and the cross sections pressed together, thread-like strands of bacterial ooze are visible when the two halves are gently pulled apart again.

What causes bacterial wilt

The bacteria overwinter in the gut of striped and spotted cucumber beetles. Not all beetles carry the bacteria. Beetles that feed on infected plants pick up the bacteria. They then move to new plants, creating wounds through feeding. The bacteria are on the mouthparts or in the fecal matter of the beetle and enter the plant through the feeding wounds.

The bacteria multiply rapidly within the plant and plug the vascular tissue, resulting in wilting of the vines. Once bacterial wilt infects a plant, there is no way to control the disease. The bacteria cannot transmit in seed, does not survive in soil, and only survives in plant debris for a short period. It cannot overwinter in Minnesota in plant debris.

Preventing and managing the disease

  • Managing cucumber beetles provides the most effective control of bacterial wilt.
  • If disease appears in a few plants, rogue and bury these plants to prevent further spread of the disease.
  • Pesticides will not help in managing a cucurbit plant infected with this bacterial disease.

Michelle Grabowski

Reviewed in 2018

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