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Ministry of Agriculture, Food and Rural Affairs

Bacterial Wilt

Bacterial Wilt Bacterial wilt Bacterial Wilt
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Beginner

Scientific Name
Erwinia tracheiphila

Identification

  • Bacterial wilt infections first develop as dull green patches on the leaves
  • As the vascular tissue becomes blocked with bacterium, the runners (and eventually the whole plant) become wilted
  • Plants ultimately turn yellow and die

Often Confused With
Fusarium wilt
Verticillium wilt
Drought stress

Period of Activity
Bacterial wilt overwinters in the stomachs of adult cucumber beetles.  Peaks in beetle activity, caused by high overwintering populations or hot, dry growing conditions will also result in higher levels of bacterial wilt in the crop.

Scouting Notes
While monitoring for other diseases, take note of any wilted plants.  If an infection is suspected, cut the infected runner close to the crown; touch the 2 cut surfaces together, slowly drawing them apart.  Under humid conditions the bacteria will cause sticky strands to appear between the 2 cut ends.

Thresholds
None established.

Advanced

Scientific Name
Erwinia tracheiphila

Bacterial wilt is a significant disease of all cucurbits.  Cucurbit species and cultivars differ in their susceptibility to bacterial wilt.  Generally speaking, cucumbers and melons are very susceptible

The striped and spotted cucumber beetles are the main vectors of this disease.  Once a plant is infected, there is no cure for bacterial wilt.  Early season infections result in the highest yield loss.  Vines that are still actively growing at the time of infection will often die without producing any marketable fruit.

Identification
Bacterial wilt infected leaves develop dull green patches followed by wilting, chlorosis and necrosis.  Bacterial wilt will often start on one leaf, spreading one leaf at a time back towards the main crown.  Plants may temporarily recover during cooler night-time temperatures, however, eventually the whole plant will become infected and die.

If the cut ends of an infected runner are placed together and slowly drawn apart, sticky strands of bacteria are sometimes visible (especially during humid conditions, or early in the day).

Often Confused With
Fusarium wilt
Verticillium wilt
Drought stress

Biology
Bacterial wilt overwinters in the intestines of the striped and spotted cucumber beetle.  As the beetles feed, they transmit the bacteria into the plant.  Once inside the plant, the bacteria multiply and colonize the vascular tissue, preventing the transport of water and nutrients to the growing tips of the infected runners.

While aphids and other insects may also transmit bacterial wilt, the cucumber beetles are considered to be the primary vector.  This disease does not survive on residue in the soil or on seed.

Period of Activity
Peaks in beetle activity, caused by high overwintering populations or hot, dry growing conditions will also result in higher levels of bacterial wilt in the crop.

Scouting Notes
While monitoring for other diseases, take note of any wilted plants.  If an infection is suspected, cut the infected runner close to the crown; touch the 2 cut surfaces together, slowly drawing them apart.  Under humid conditions the bacteria will cause sticky strands to appear between the two cut ends.

Thresholds
None established.

Management Notes

  • Control cucumber beetle feeding to prevent the spread of this disease.
  • The percentage of cucumber beetles harbouring bacterial wilt tends to increase dramatically over the course of the summer. 
  • Early season infections, while the plants are still actively growing, may result in substantial yield losses.