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Plectosporium blight (Plectosporium tabacinum), formerly called Microdochium blight, primarily affects pumpkin, but all cucurbits are susceptible. Symptoms include elongated, white lesions that are approximately 1/4-inch in size. Stems, petioles, and leaf vein lesions are diamond shaped; lesions expand and coalesce causing leaf death and blighting. Large circular patches of affected vines may be visible. Lesions on fruit are usually round and remain small, dry, and scabby.

Plectosporium blight on pumpkin fruit.

(Photo: William Nesmith, University of Kentucky)

Plectosporium blight on pumpkin foliage.

(Photo: Kenny Seebold, University of Kentucky)

Plectosporium blight on pumpkin stem.

(Photo: Kenny Seebold, University of Kentucky)

Management:

• Space plants for air circulation and rapid drying.
• Apply protectant fungicides beginning at fruit set.
• 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.

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