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Bacterial wilt of cucurbits

Quick facts

  • Bacterial wilt can cause severe losses in cucumbers and muskmelons. It is less common and less severe in pumpkins and squash.
  • Plants wilt in the field. They often recover overnight but continue to wilt each day.
  • Wilt is often isolated to a small area or individual plants. 
  • Wilt progresses down the vine until the entire vine wilts or dies.
  • Leaves eventually yellow and brown at the margins, then completely wither and die.
  • 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 cure a cucurbit plant infected with bacterial disease.
A field of pumpkin plants, with a yellow, wilting plant in the foreground.
Bacterial wilt in pumpkin

How to tell bacterial wilt apart from other cucurbit issues

  • 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.
  • The speed of wilting 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. This method is not always effective because the threads can be hard to see without a microscope. If you see the thread-like strands, you can assume that you are seeing bacterial wilt. However, if you do not see them, you may still have bacterial wilt.
A bisected cantaloupe vine being pulled apart to reveal threads of bacterial ooze between the two halves.
Bacterial streaming in a cantaloupe stem infected with bacterial wilt
Two yellow and black striped cucumber beetles feeding on a plant.
Striped cucumber beetle feeding and feces spread bacterial wilt.

Biology

  • 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. 
  • 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.
  • Bacterial wilt does not occur every year in Minnesota.

Managing bacterial wilt in the garden

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How to manage bacterial wilt on the farm

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Authors: Marissa Schuh, horticultural IPM Extension educator, and Michelle Grabowski

Reviewed by Annie Klodd and Natalie Hoidal, Extension educators

Reviewed in 2022

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