Cucumber Phytophthora Blight

1
Managing Phytophthora Blight of Cucumber
W. R. Stevenson UW - Madison Dept of Plant
Pathology
2
Phytophthora Blight - Key Points

• Pathogen Phytophthora capsici
• Symptoms
• Rapid wilting of individual plants, vascular
  browning
• Watersoaked areas on fruit
• Rapid enlargement of fruit lesions
• White fungal growth covers fruit lesion
• Rapid collapse of affected fruit
• Favored by warm and wet conditions
• Spread by rain splash, insects, workers
• May overwinter in crop debris and in soil

3
Phytophthora Blight

• Pathogen Phytophthora capsici
• Symptoms
• Rapid wilting of individual plants, vascular
  browning
• Watersoaked areas on fruit
• Rapid enlargement of fruit lesions
• White fungal growth covers fruit lesion
• Rapid collapse of affected fruit

4
Phytophthora Blight - Control Strategies

• Pathogen-free seed
• Crop rotation minimum of 3 years
• Plant in well-drained sites
• Avoid over-irrigation
• Do not enter fields with wet foliage
• Prompt tillage of infected debris at season end
• No known resistance
• Fungicide controls being evaluated

5
Cucumber Fungicide Trial, 1998 Control of
Phytophthora Blight
Incidence of Diseased Vines ()
6
Cucumber Fungicide Trial, 1998 Control of
Phytophthora Blight
Incidence of Diseased Fruit ()
7
Cucumber Fungicide Trial, 1998 Control of
Phytophthora Blight
Incidence of Diseased Fruit After 1 week storage
()
8
Cucumber Fungicide Trial, 1998 Control of
Phytophthora Blight
Yield of Fruit/10 row (lb)
9
Cucumber Fungicide Trial, 1999 Control of
Phytophthora Blight
Incidence of Diseased Vines ()
10
Cucumber Fungicide Trial, 1999 Control of
Phytophthora Blight
Incidence of Diseased Fruit ()
11
Cucumber Fungicide Trial, 1999 Control of
Phytophthora Blight
Yield of Fruit/10 row (lb)
12
Cucumber Fungicide Trial, 1999 Control of
Phytophthora Blight
Incidence of Diseased Fruit After 1 week storage
()
13
Cucumber Fungicide Trial, 2000Control of
Phytophthora Blight
Incidence of Diseased Vines ()
14
Cucumber Fungicide Trial, 2000Control of
Phytophthora Blight
Incidence of Diseased Fruit ()
15
Cucumber Fungicide Trial, 2000Control of
Phytophthora Blight
Yield of Fruit/10 row (lb)
16
Cucumber Fungicide Trial, 2000Control of
Phytophthora Blight
Incidence of Diseased Fruit After 1 week storage
()
17
Phytophthora Blight Summary

• Disease observed on cucumber, pumpkin, squash and
  pepper
• Problem is widespread and increasing
• Rotation at least 3 years to non susceptible
  crop - e.g. corn
• Chemical controls are effective for now
• Ridomil Gold at planting
• During fruit growth phase Acrobat MZ (Sect. 18
  label??)
• of sprays depends on weather

18
Phytophthora Blight Summary

• Proactive management of resistance to fungicides
  is critical
• Resistance to Ridomil Gold already observed in
  other states
• Use of Ridomil Gold as sole control is dangerous
• If use of Ridomil Gold, then should also use
  Acrobat MZ on foliage and fruit