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M. Grabowski, University of Minnesota
Choanephora Rot, also known as blossom end rot or wet rot, is a disease most commonly found on summer squash under wet conditions. This disease has been seen occasionally on other cucurbits including pumpkin and vegetable marrow.
- Flowers are covered with first white then purplish black fungal growth
- The blossom end of the squash is soft, rotted and covered in fluffy purplish black fungal growth'
Choanephora rot is caused by the fungus Choanephora cucurbitarum. The fungus survives from season to season in crop debris and is spread to new flowers by insects, splashing water, or wind. Infection most commonly occurs on flowers, although the fungi can also infect through wounds on the fruit. Infected flowers are soft, rotted and quickly become covered with first white then purplish black fungal growth. In female flowers, the infection progresses into the fruit and results in soft water rot of the blossom end of the squash. The fungus thrives in wet conditions.
- Fungicides are ineffective against Choanephora rot because new susceptible flowers open every day.
- Rotate out of cucurbits.
- Avoid overhead irrigation.
- Space plants to provide adequate air movement in the field to quickly dry flowers and fruit.
- Raised plant beds and plastic mulch may be of help to limit fruit contact with moist soil and reduce moisture in the lower plant canopy.