Downy Mildew Spores Identified in Michigan

4 views of downy mildew symptoms on cucumber

1-2: Early symptoms of downy mildew on cucumber with the yellow-brown tissue bordered by the leaf veins. 3-4: The dark spores of the cucumber downy mildew pathogen can be seen on the underside of the leaf. These spores move via air currents and infect unprotected plants. Photos by Mary Hausbeck, MSU.

The Hausbeck lab at Michigan State University reported that downy mildew spores have been detected in sport traps in Michigan.

“A cucurbit downy mildew disease outbreak on cucumber plants has not been reported in Michigan at this time. While it is concerning that an influx of sporangia has been detected, these sporangia must land on a suitable plant such as a cucumber or melon and then the weather conditions must allow the spore to germinate and infect. It is recommended that growers and scouts keep a close eye on cucumber and melon plantings that may have been established under low or high tunnels.”

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