Plant Disease Management Handbook

Cause The fungus, Cladosporium cucumerinum, which overwinters in cucurbit debris in soil, in greenhouse cracks and corners, and on seed. It can infect and severely injure fruit at all growth stages, particularly when young. Spores can travel long distances in moist air and can also be disseminated by insects, clothing, and tools. They penetrate the host less than 9 hours after germination; infection is visible in 3 days, and spores may be produced in 4 days.

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Squash (Cucurbita spp.) - Damping-off

Cause Several Pythium spp. have been described. P. aphanidermatum causes a sudden wilt. Cool, wet soils favor these fungus-like microorganisms.

Cause The fungi, Golovinomyces cucurbitacearum (formerly G.

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Squash (Cucurbita spp.) -Blossom-end Rot

Cause Lack of pollen or inactive pollen.

Cause A fungus, Stagonosporopsis caricae (syns. Stagonosporopsis citrulli, Stagonosporopsis cucurbitacearum, Didymella bryoniae, Phoma cucurbitacearum), which overwinters in associaton with infected crop debris for at least two years. This fungus can also be seedborne. Numerous other cucurbits are affected, including cantaloupe, watermelon, cucumber, and pumpkin.

Cause The fungus, Fusarium oxysporum f. sp. cucurbitacearum, which lives in soil.

Symptoms Plants may wilt slowly as foliage yellows or may wilt suddenly without yellowing. Wilting is most severe during water stress. In cross-section, the lower stem shows darkened vascular tissue. May be confused with symptoms of Verticillium wilt.

Cultural control

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Cucumber (Cucumis sativus) - Downy Mildew

Cause The fungi or fungus-like microorganisms, Pythium spp., Fusarium spp., and Rhizoctonia solani, attack many vegetable seedlings including members of the genus Cucurbita. Seedlings are very susceptible to infection just before and just after they emerge from soil.

Cause The beet curly top virus, which is transmitted by the beet leafhopper.

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Squash (Cucurbita spp.) - Storage Rots

By Cynthia M. Ocamb and Hannah Rivedal