Cucurbit Wet Rot

Are your squashes rotting on the vine? It may be cucurbit wet rot.

Yellow summer squash infected with cucurbit wet rot (Howard F. Schwartz, CSU, Bugwood.org) CC BY 2.0 US

Cucurbit wet rot is caused by Choanephora cucurbitarum fungi. Also known as Choanephora fruit rot and wet rot, this fungal disease also affects melons, pumpkins, and other cucurbits, as well as beans and peas, and okra.


Cucurbit wet rot symptoms

Cucurbit wet rot first appears as a soft area on the blossom end of fruit or pods. Those soft spots can also appear around wounds in the fruit. Those softened areas become covered with soft white fungal growth that eventually turns purplish-black. Eventually, the entire fruit rots.

Cucurbit wet rot is often confused with blossom end rot and Rhizopus soft rot.

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Blossom end rot looks like leathery, dark areas on the flower end of your fruit. It happens most often on tomatoes. There’s really nothing soft or squishy about it. Cucurbit wet rot is wet and squishy and distinctly rotten. We’ll get to Rhizopus soft rot tomorrow.

Blossom end rot (Mark) CC BY 2.0

Cucurbit wet rot (David B. Langston, UGA, Bugwood.org) CC BY 3.0

Cucurbit wet rot management

Like most things that are rotting, cucurbit wet rot needs moisture to turn into a problem. You can prevent it with good drainage and by allowing the soil to dry out between waterings. Fungal spores can travel on the wind, with insects, or in splashing water. While there isn’t anything we can do about the wind, there are things we can do to prevent wet rot:

• keep insect populations in check
• avoid overhead watering
• space plants for good airflow and quick drying
• use crop rotation

Once a fruit is infected, it should be removed and tossed in the garbage.