Michigan hop scouting report – May 18, 2016

Glyphosate damage and downy mildew are common sights in the hopyard this week.

Glyphosate-damaged hop bine. Note the strappy upper leaves, green leaf veins and stunted appearance. All photos: Erin Lizotte, MSU Extension.

Glyphosate-damaged hop bine. Note the strappy upper leaves, green leaf veins and stunted appearance. All photos: Erin Lizotte, MSU Extension.

Hops around Michigan are coming along nicely, with bines in the north measuring up to 4 feet. Growers have completed stringing for the most part and some have begun training on early varieties. Early sidedress applications of fertilizer have been completed and with dry weather in the forecast, irrigating and fertigating will pick up soon.

Most growers report having made multiple fungicide applications for controlling downy mildew already. There will be significant disease pressure early due to carryover from intense downy mildew infections in 2014-15. For more information on managing downy mildew, read “Controlling downy mildew on hop” by Michigan State University Extension plant pathologist Mary Hausbeck.

At this time of the season, it can be difficult to tell the difference between downy mildew spikes and growth damaged by glyphosate; they both appear yellowed and stunted. Shoots damaged by glyphosate are stunted and the leaves take on a strappy, thinned appearance, producing leaves that are yellow with green veins. Downy-infected spikes are stunted with cupped leaves and exhibit a general yellowing, including the leaf veins. The lower leaves on downy-infected spikes are often blackened and the gray-black mat of spores from the fungi may be visible on these lower leaves. Glyphosate damage from early spring applications is sporadic but not uncommon; downy mildew spikes are prevalent in some yards this spring.

Downy mildew-infected hop spike

Downy mildew-infected hop spike. Note the stunted appearance, cupped leaves, general yellowing and the blackened lower leaves.

Please continue to visit the MSU Extension Hops website and the MSU Hops News Facebook page for up-to-date information, as well as sign up for the MSU Extension Hop & Barley Production Newsletter for current news articles and events. Also, please sign up for the new MSU Hop listserv for a lively interactive discussion of all things hop-related. To subscribe:

  • Send an email to: .(JavaScript must be enabled to view this email address)
  • Leave the “subject” line blank
  • In the body of the email type: SUBSCRIBE Hops
  • You will receive a confirmation email directing you to click on a link (this is to avoid spammers). Click on the link.
  • To send an email to the list once you have joined, just send it to: .(JavaScript must be enabled to view this email address)

This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2015-09785. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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