Jul 29, 2009
Downy Mildew Outbreak on Michigan Cucumbers, Onions

Downy mildew on cucumbers has been found in several counties across Michigan this week. In general, the number of plants infected has been low, but given the continued cool, wet weather, it will not take long for the disease to spread and cause rapid blighting and plant death.

It is crucial that growers protect those crops that are most susceptible. It is clear that cucumbers and melons are most susceptible to downy mildew, but we are getting reports from other states that the other vine crops are also at some risk of developing downy mildew.

At this juncture, all cucumbers and melons across the state must be protected with fungicides immediately. Do not wait for disease to develop because then it may be too late. All other vine crops must be watched very closely for anything that is peculiar and samples should be brought to an Extension office or to Michigan State University Diagnostic Services.

Although the pumpkins, winter and summer squash, zucchini and gourds have not readily developed downy mildew in past years, this summer’s weather is not typical and is extremely favorable for downy mildew development. I do not want growers of pumpkins, squashes, etc. to believe that their crops are immune from downy mildew. All bets are off as a result of this weather!

For more information about downy mildew on cucumbers, Click here. For information about downy mildew on onions, Click here.

Mary Hausbeck
Michigan State University Extension

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