Extension Logo
Extension Logo
University of Minnesota Extension
https://extension.umn.edu

Choanephora rot

Quick facts

  • Choanephora rot is a disease most commonly found on summer squash under wet conditions.
  • The blossom end of the squash is soft, rotted and covered with fluffy purplish black fungal growth.
  • The fungus survives from season to season in crop debris and moves 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.
  • Avoid overhead irrigation.
  • Space plants to provide enough air movement in the field to quickly dry flowers and fruit.

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 also infects other cucurbits including pumpkin and vegetable marrow.

Identifying Choanephora rot symptoms

  • White, then purplish black fungal growth, covers the flowers.
  • The blossom end of the squash is soft, rotted and covered with fluffy purplish black fungal growth.

What causes Choanephora rot

  • The fungus Choanephora cucurbitarum causes Choanephora rot.
  • The fungus survives from season to season in crop debris and moves 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 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.

Preventing and managing the disease

  • Fungicides are ineffective against Choanephora rot because new susceptible flowers open every day.
  • Rotate out of cucurbits.
  • Avoid overhead irrigation.
  • Space plants to provide enough air movement in the field to quickly dry flowers and fruit.
  • Raised plant beds and plastic mulch may limit fruit contact with moist soil and reduce moisture in the lower plant canopy.

Michelle Grabowski

Reviewed in 2018

Share this page:

© 2019 Regents of the University of Minnesota. All rights reserved. The University of Minnesota is an equal opportunity educator and employer.