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Downy Mildew is Continuing to Spread Across the Eastern U.S.

Posted: July 22, 2015

Although there have been no new confirmed reports in Pennsylvania, reports of downy mildew are continuing to increase across the eastern half of the U.S.
Highlighted counties are where CDM outbreaks have been reported as of 22 July 2015. Red indicates that the reports were made within the past 7 days. Map source: Cucurbit Downy Mildew ipmPIPE website.

Highlighted counties are where CDM outbreaks have been reported as of 22 July 2015. Red indicates that the reports were made within the past 7 days. Map source: Cucurbit Downy Mildew ipmPIPE website.

The most recent and closest reports were on giant pumpkin and butternut squash in northern New Jersey. In PA, downy mildew has been confirmed on cucumber in Elk and Berks Co. and on butternut squash in Lancaster Co. Currently, we are following up on an unconfirmed report of downy mildew on cucumber in the Lawrence, Butler and Mercer Co. area.

The drier conditions forecasted of the next few days place the vast majority of Pennsylvania at minimal risk except for some very local spread in already infected fields.

If you are not already doing so, it is important to be regularly scouting your cucurbit fields. It takes several days for symptoms to develop after infection and conditions this past weekend were very favorable for disease development. Look at both the upper and lower leaf surface. If you have been applying protectant fungicides then the sporulation may not be as obvious.

For the latest information on outbreaks and to receive email or text alerts please visit the Cucurbit Downy Mildew Forecasting website. Updates will also be made to the 1-800-PENN-IPM hotline weekly or more frequently if needed to provide growers with information that can be used to help make timely management decisions. The forecasted risk maps are also based on knowing where there are downy mildew infected fields (sources of the pathogen) so it is important if you suspect downy mildew on your farm to let me know either by email or by phone at 814-865-7328 or contact your local Penn State Extension Office.

Contact Information

Beth K. Gugino
  • Associate Professor Vegetable Pathology
Phone: 814-865-7328