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Summer Squash Fruit Symptoms

Originally prepared for Vegetable MD Online by Thomas A. Zitter.

This page includes symptoms caused by:

Bacteria

Angular leaf spot | See factsheet for more information (LIHREC)

Symptoms: Brown spots, 1-4 mm in diameter, circular, water-soaked often with raised white center. Leaf symptoms also present.

Bacterial leaf spot | See factsheet for more information (LIHREC)

Symptoms: Brown spots varying greatly in size (up to a half dollar). Can develop into a water soaked rot that leads to fruit collapse. Leaf symptoms also present.

Fungi & Oomycetes

Anthracnose | See factsheet for more information (LIHREC)

Symptoms: Dark brown spots, circular, 2-5 mm, or larger in diameter, sunken with salmon-colored fungal growth under moist conditions or tiny black specks. Spots often develop in storage. Leaf and stem symptoms also present.

Choanephora fruit rot | See factsheet for more information (LIHREC)

diseased summer squash fruit
Photo courtesy of Meg McGrath, Cornell University, LIHREC, NY.

Symptoms: Symptoms usually start to develop at the blossom end of fruit touching the ground. Affected tissue develops a wet, soft rot. The pathogen’s growth is distinctive. It looks furry (hairy) and like a lot of pins in a pin cushion. Blossoms and leaves can also be affected.

Fusarium dry rot | See factsheet for more information (LIHREC)

Symptoms: Tan, circular spots that develop into a firm dry rot with white fungal growth. On surface side touching moist soil. Uncommon.

Gummy stem blight | See factsheet for more information (LIHREC)

close-up of diseased summer squash fruit
Extensive black rot infection on spaghetti squash (C. pepo). Photo courtesy of T.A. Zitter, Cornell University, Ithaca, NY.

Symptoms: Black spots, circular or irregular, can be large. Initially water-soaked, pinkish then turning black. Fruit often collapse due to other rotting organisms. Symptoms often develop in storage. Pycnidia often develop in storage. The foliar phase is called gummy stem blight black rot.

Phytophthora fruit rot | See factsheet for more information

three diseased squash fruit
Photo courtesy of Meg McGrath, Cornell University, LIHREC, NY.

Symptoms: Water-soaked or sunken spots which enlarge to encompass the entire fruit. White yeast-like fungal growth. Leaf and stem symptoms also present. Localized occurrence.

Plectosporium blight | See factsheet for more information (LIHREC)

two diseased summer squash fruit
Photo courtesy of Mary Ann Hansen, Virginia Polytechnic Institute and State University.

Symptoms: Light tan spots, small spindle-shaped, sunken, dry, scabby. Spots primarily on fruit handles, stems, and sometimes on leaves.

Pythium rot

diseased summer squash fruit
Photo courtesy of Meg McGrath, Cornell University, LIHREC, NY.

Symptoms: White spots, circular, 1-2 mm in diameter, raised like a rash. Leaf symptoms also present.

Scab

two diseased summer squash fruit
Fleshy fruit are especially susceptible to scab infections and subsequent crop losses. Photo courtesy of T.A. Zitter, Cornell University, Ithaca, NY.

Symptoms: Beige or brown spots, dry and corky, small, circular. Initially sunken but can become raised. Leaf and stem symptoms also present.

Sclerotinia white mold

Symptoms: Watery, odorless rot. The pathogen produces a white cottony mold with black, hard, pea-like bodies. Develops in field or in storage. Localized occurrence, especially where beans or cabbage were grown.

Septoria

Symptoms: White spots, circular, 1-2 mm in diameter, raised like a rash. Leaf symptoms also present.

Phytoplasmas

Aster yellows

diseased summer squash plant and fruit
Photo courtesy of T.A. Zitter, Cornell University, Ithaca, NY.

Symptoms: Fruit smaller and lighter in color than normal. Leaf symptoms also present.

Viruses

Watermelon mosaic virus | See factsheet for more information (LIHREC)

several diseased summer squash fruit
Photos courtesy of T.A. Zitter, Cornell University, Ithaca, NY.

Symptoms: Fruit mottled, discolored (e.g. green blotches), distorted, bumpy, malformed. The whole plant may be stunted. Leaf symptoms also present.

Papaya ringspot virus | See factsheet for more information (LIHREC)

two diseased and one healthy summer squash fruit
Photos courtesy of T.A. Zitter, Cornell University, Ithaca, NY.

Symptoms: Fruit mottled, discolored (e.g. green blotches), distorted, bumpy, malformed. The whole plant may be stunted. Leaf symptoms also present.

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