Black root of cucurbit is caused by a soil fungus; it affects cucumbers
Black root of cucurbit (Phomopsis sclerotioides) is caused by a soil fungus. This fungus affects cucumbers, although melon and gherkin are also susceptible. Young plants lag behind in growth and wilt because water absorption is disrupted. The roots are underdeveloped and turn black due to the formation of fungal spores.
Symptoms may resemble those of Fusarium rot and Verticillium spp.
Control
Black root of cucurbit cannot be controlled; affected plants should be removed as soon as possible to prevent infestation of other plants.
Prevention
Do not plant cucumbers in areas where soil fungus may be suspected to be active; regular crop rotation helps prevent Black root of cucurbit.