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Why Does Yellow Squash Rot on the Vine?

By Irum Sarfaraz ; Updated September 21, 2017
Squash belongs to the cucurbit family.
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Squash is a warm-season vegetable from the cucurbit family that also includes pumpkins, watermelons and cucumbers. Squash comes in a variety of shapes and colors, including yellow, and grows on prostrate vines with bright yellow flowers. A fungal disease causes the vegetable to start rotting on the vine.


Squash is susceptible to black rot disease, a phase of gummy stem blight, caused by Didymella bryoniae. The fungus infects the vegetable both prior to harvest in the field and while in storage.


The disease starts with yellow, irregular spots on the vegetables. With time the spots become grayish-brown and water-soaked and eventually turn black. Rotting areas become wrinkled and dark dots form fungal fruiting bodies. As spots enlarge, they take on a sunken look.


Use well drained soil for planting and avoid overhead irrigation as excessive moisture favors fungal growth. Control powdery mildew fungus on the vegetables as this makes plants prone to black rot fungus. The University of Connecticut Extension recommends curing harvested squash at 85 degrees Fahrenheit for two weeks prior to storage.


About the Author


Irum Sarfaraz is a freelance writer with over 20 years of nonfiction writing experience in newspaper op-eds and magazine writing, book editing, translating and research writing. Sarfaraz is originally from Pakistan and has been published in both American and Pakistani newspapers and magazines. She holds a Bachelor of Arts in English literature, and diplomas in nonfiction writing.