Scab of Cucurbits
Cucumber with Lesions
Symptoms on Foliage
Lesions on Squash
Pumpkin with LesionsHOSTS
- Cucurbits
DESCRIPTION
Scab, caused by the fungus Cladosporium cucumerinum, can cause significant damage to the foliage and fruit of cucurbits. While all cucurbits can be affected, resistant cultivars are available for some crops, specifically cucumbers. Watermelons are considered highly resistant to this disease.
BIOLOGY
C. cucumerinum overwinters on infected crop debris. Spore production begins when temperatures warm (59 °F to 77 °F) and conditions are moist. These spores can be spread by the wind, water, or through contact with insects, equipment, or people. Once a spore reaches a suitable host, it can invade the plant in as little as 9 hours. Symptoms can appear within 3 days, a new spores will be produced within 4 days.
Secondary infections, such as soft-rot bacteria, are common with severe scab infections. The secondary infections will increase the rate at which the fruit rots.
SYMPTOMS
- Gray to brown, lesions with yellow halos on foliage.
- Foliar lesions with the center dry or fallen out, causing a ragged appearance.
- Small, sunken spots on fruit that ooze.
- Large, discolored cavities in fruit that may extend deep into the fruit.
- Raised, misshapen lesions on resistant fruits.
- Green or black fungal growth on fruit.
GENERAL MANAGEMENT
- Use certified disease-free seeds.
- Choose scab-resistant plant varieties when available.
- Rotate with non-cucurbit crops for 2-3 years.
- Avoid watering practices, such as overhead irrigation, that result in wet soil and plants for prolonged periods.
- Avoid working with plants when wet.