Michigan Cucurbit update | July 26, 2023

  • Summer squash, cucumbers, pickles and melons are being harvested.
  • Watermelons and hard squash are setting fruit.
  • Late June high temperatures caused widescale fruit abortions that were noticed five to 10 days later.
  • Hot night time temperatures may also have a suppressive effect on fruit set.
  • Reports of virus symptoms in squash were received this week.
  • The first symptoms of cucurbit downy mildew disease on pickling cucumber plants in a commercial production field were verified by the MSU vegetable pathology lab.
  • Look for weekly spore trap updates and current downy mildew news on the Hausbeck Lab Downy Mildew News website.
  • Early season dry conditions likely delayed downy mildew development. More frequent dew periods and rainfall now is favorable for the pathogen (Pseudoperonospora cubensis) and a rapid escalation of the disease is likely if fungicide sprays are delayed.

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yellow fruits on left yellowing leaf on right

Symptoms caused by a potyvirus in both fruit and foliage of yellow squash. Photos by MSU Plant & Pest Diagnostics.