Southern Blight of Cucurbit Crops
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Southern blight (Athelia rolfsii, syn Sclerotium rolfsii) occurs primarily on cucumber, melons, and pumpkin. Symptoms begin as wilting followed by plant death. Lesions or cankers develop at the base of infected stems near the soil line. White fungal growth and numerous small, round, tan-to-reddish fungal survival structures (sclerotia) develop at the crown. Fruit infections begin when the fruit comes into contact with the soil surface. Affected areas are soft, water-soaked, and covered with a dense mat of white, fan-like fungal growth; sclerotia may develop on fruit at the soil line.
Southern blight on pumpkin.
(Photo: Kenny Seebold, University of Kentucky)
Close-up of sclerotia.
(Photo: Kenny Seebold, University of Kentucky)
Management:
- Space plants for air circulation and rapid drying.
- Promptly remove and destroy diseased plant material during the growing season.
- Manage weeds and potential alternative hosts.
- Avoid movement of infested soil to clean fields.
- Promptly destroy crop residues after harvest.
- Deep plow to bury residual inoculum.
- Rotate with nonhost crops for at least 3 years.
- Limited fungicides are available, and efficacy of these fungicides can be variable.
