Think you found hop powdery mildew in your yard?

Bill Weldon, a graduate student at Cornell University, is conducting research on hop powdery mildew for his PhD thesis. He is trying to collect as many samples of hop powdery mildew from around the country as he can, and is asking for your help should you encounter powdery mildew in your hopyard or in areas of wild hops this season. The goal of his project is to better understand the diversity found within powdery mildew populations around the country. There are two mating types (aka “aka genders”) of powdery mildew and knowing whether both genders are present within a given yard directly impacts how we manage the disease. This sample collection will also help take steps to monitor for the development of fungicide resistance in hop powdery mildew populations.

Should you find any hop powdery mildew, please e-mail Bill immediately at and he will overnight you a sample collection kit. The sample collection process is very quick and easy. Essentially, you are just using small stickers to peel off hop powdery mildew from the surface of the infected leaf and placing the sticker in a little tube. It’s important to choose powdery mildew colonies that have a distinct round edge and haven’t grown to the point where it is merging with other colonies on the leaf. Ideally, 12 samples should be collected from each yard, evenly distributed throughout the rows of affected plants, so that he can accurately look at the diversity within the yard. Feel free to contact Bill with any questions about his project.

For more information about powdery mildew management in hops, check out Michigan State University IPM educator Erin Lizotte discussing that very topic for our most recent Hops Power Hour (, and the following article on our website:

And if you did find powdery mildew in your yard, remember to keep calm and hop on…

Powdery mildew on hop leaf. Photo credit: David Gent, USDA Agricultural Research Service,

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