Michigan hop crop report for the week of June 7, 2021

Growers experienced hot and dry weather across the state.

Fuggle hops
Fuggle hops in northeast Michigan on June 8, 2021. Photo by Andrew Walawender.

Weather

Most areas of the state experienced above normal temperatures recently, which was quite a shift from the previous week’s below normal temperatures. Drought conditions persist across most areas. Areas in southwest and southcentral Michigan are well below the five-year precipitation average, although there is a chance of rain across southern Michigan over the next few days.

Temperatures are forecasted to drop by the end of the week, followed by more moderate conditions before climbing again. The 6-10 day forecast suggests a greater probability of above-normal temperatures and below normal precipitation for June 13-17, 2021.

Watch the most recent agricultural weather forecast from Michigan State University state climatologist Jeff Andresen.

June 7 hop rainfall
Accumulated rainfall summary for hop producing areas of Michigan on June 7, 2021, as compared to the five-year average. Data from MSU Enviroweather.
june 7 GDD Hops
Accumulated degree day (base 50 F) summary for hop producing areas of Michigan on June 7, 2021, as compared to the five-year average. Data from MSU Enviroweather.

Stage of production/physiology

With warmer weather over the last few days, hops have begun to grow rapidly across most areas of the state. Hops across Michigan are in Principal Growth Stage 3: Elongation of Bines (see chart). Most growers are actively watering and fertilizing.

Average Michigan hop growth stage chart.

Average Michigan hop growth stage based on date. Botanical drawings courtesy of Dodds, Kevin. 2017. Hops, a guide for new growers. NSW Department of Primary Industries.
Timing of hop production chart.
Timing of hop production management activities in northwest Michigan.

Hop growth stage chart.

Crop development

Southeast Michigan

Hot, humid conditions persist in southeast Michigan. Growers have seen some precipitation over the last week, but rainfall is still below the five-year average. Most hops are 12-14 feet, although some have hit the wire. Burndown herbicides are being applied and mites have been spotted.

Hops
Hops are 12-14 feet tall in southeast Michigan as of June 7, 2021. Photo by Rose Stahl.

Southwest Michigan

Hops are 6-12 feet up the string and growing quickly. Cascade and Saaz are into the 10-12 feet range and other varieties are 6-10 feet. Growers are actively irrigating and have begun fertilizing, which will likely continue through July 4. Growers have treated for European corn borer. Adult mites have been counted at two to five per leaf; growers may want to keep an eye on mite numbers and consider spraying. Halo blight has been spotted as well, which is earlier than usual.

East central Michigan

Hop height varies by cultivar from 6-10 feet. A few hard ahead of schedule and a few seem a bit behind schedule. Leaf hoppers and moths have been spotted as well as a bit of downy mildew on Centennial in particular. Quite a bit of deer browsing has been reported but doesn’t seem to be affecting growth. Everything is progressing well.

West central Michigan

Hop bines are averaging 6-8 feet in height but are variable by based on management and variety. Growers are irrigating and fertilizing.

Northeast Michigan

Most plants are 8-10 feet tall. Fertigation and irrigation are in full swing. Growers have preventatively sprayed for Downy mildew and sprayed for leaf hoppers since pressure has been moderate recently. Dry conditions persist.

Northwest Michigan

Growers are actively irrigating and fertilizing. Heights range from 6-10 feet. A little downy mildew and leaf hoppers have been spotted.

Low-trellis Summit hops
Low-trellis Summit hops in northwest Michigan on June 7, 2021. Photo by John Hardy.

Weeds

Growers should minimize competition from weeds, which can compete for water and nutrients. As a reminder, weeds are best controlled when they are small. 

Diseases

Downy mildew spikes have been seen in southwest Michigan for the past few weeks. Since we have rain in the forecast downy mildew will likely increase and develop into secondary downy mildew on lateral shoots if left uncontrolled. Most growers have made one to two chemical applications already. Several effective foliar fungicides are available and include products in FRAC codes 4, 11, 21, 40, 43, 45 and 49. See the MSU Extension article, “Managing hop downy mildew in Michigan,” for more information on management methods for downy mildew and refer to the Michigan Hop Management Guide. This is a critical time to control downy mildew to prevent the development of lateral downy mildew and additional spikes in the yard.

We observed a few flagged powdery mildew shoots in southwest Michigan on May 18. These are hard to spot shoots covered with white sporulation. In Michigan, because powdery mildew appears to be more sporadic, using clean planting material when establishing new hop yards can be a very useful strategy since it is readily spread via nursery stock. Please consult the MSU Extension article, “Managing hop powdery mildew in Michigan in 2020,” for more specific details about how to manage powdery mildew using other cultural practices and chemical applications.

Now is a great time of year to look for viral disease symptoms on new growth. On June 1, we observed a Centennial plant that is known to be infected with four viruses: 1) American hop latent virus, 2) hop latent virus, 3) hop mosaic virus and 4) hop stunt viroid. The best way to control viruses is to utilize sanitation practices prior to planting (e.g., using virus tested stock, destroy heavily symptomatic plants). For more information about hop viruses, please check this article Virus visible in Michigan hopyards.

On May 28, we began to observe foliar halo blight in hopyards. These infections are caused by a fungus. This fungus is a Diaporthe sp. and researchers at Michigan State University have been studying management methods for the past two years. Halo blight can be a serious disease in specific yards and lead to significant cone infections and ultimately shatter during harvest. It appears to have a wider geographic range than previously thought and has been recovered throughout Michigan on both leaves and cones. How the pathogen survives during the winter, spreads, causes new infections is still being investigated. The goal is to provide management tools that can be used to prevent foliar and cone infections in yards. 

Early symptoms of halo blight
Early symptoms of halo blight on leaves of on Chinook in southwest Michigan. Photo by Timothy Miles, MSU.
Typical symptoms of halo blight on leaves
Typical symptoms of halo blight on leaves of on Chinook in southwest Michigan. Note the chlorotic halo surrounding the lesion. Photo by Timothy Miles, MSU.

Insects

Twospotted spider mite activity has begun but remains at low levels and tough to spot. Twospotted spider mite is a significant pest of hop in Michigan and can cause complete economic crop loss when high numbers occur. Feeding decreases the photosynthetic ability of the leaves and causes direct mechanical damage to the hop cones. Leaves take on a bronzed and white appearance and can defoliate under high pressure. Intense infestations weaken plants, reducing yield and quality. Dry, hot weather provides ideal conditions for outbreaks.

Scout carefully for mites season long and treat while populations are at low levels when mites are most effectively managed. Refer to the Twospotted Spider Mite Factsheet for more information on identification and management.

Twospotted spider mite adult
Twospotted spider mite adult along hop midvein under magnification. Photo by Erin Lizotte, MSU Extension.

Potato leafhopper have arrived from Gulf states where they can overwinter but are still at low numbers. Like many plants, hops are sensitive to the saliva of potato leafhopper, which is injected by the insect while feeding. Damage to leaf tissue can reduce photosynthesis, which can impact production, quality, and cause death in baby plants. Refer to the Hop Potato Leafhopper Factsheet for more information on identification and management.

Adult potato leafhopper on hop leaf.
Adult potato leafhopper on hop leaf. Photo: Erin Lizotte, MSU Extension.

European corn borer remains a concern this year, particularly on sites with infestations in 2019-20. European corn borer has been a minor pest of hop in Michigan over the last decade. Other Midwestern states have experienced more substantial damage from this introduced moth. Unfortunately, damaging levels of European corn borer larvae were present in some Michigan hopyards for the last two years. The Enviroweather corn borer model has predicted adult moth emergence in all major hop production regions in Michigan at this time.

Regardless of location, scout for adults, eggs and larvae now. For more information on European corn borer, refer to the MSU Extension article, “Be on the lookout for European corn borer in hops.”

6-2 Hop report 9 web
European corn borer egg mass ready to hatch. May 31, 2021. Photo by Mike Reinke, MSU Extension.

Predicated emergence of European corn borer* 

Region

Date

Southwest

5/24/2021

Southeast

5/30/2021

West Central

6/2/2021

East Central

5/26/2021

Northwest

6/6/2021

Northeast

6/5/2021

*Based off Enviroweather forecasting. 

Gypsy moth larvae have been observed feeding on a number of agricultural crops and might event munch on a hop leaf. Growers with hopyards adjacent to oak-dominated forests may see increased pressure and should keep an eye out for this dark, fuzzy caterpillar. Insecticides containing Bacillus thuringiensis (i.e., Bt) will be effective, particularly when caterpillars are small. For more information on identifying gypsy moth and their lifecycle visit the MSU Gypsy Moth webpage.

Fertility

Hops now require supplemental nutrients and growers should be fertilizing. As a reminder, June-mid July is when hops uptake the majority of nutrients required for the season. please reference the Nutrient Management section (pages 22-26) of the Michigan Hop Management Guide for fertility recommendations. MSU recommends submitting soil samples each spring around the same time (now would be a good time if you have yet to do so). Please refer to lab sampling and submission instructions prior to sending in samples.

As hops approach 8 feet in height, consider pulling leaf plus petiole samples for nutrient testing. Many soil testing labs also offer plant nutrient testing as well. For more information on hop leaf plus petiole sampling, please refer to “The importance of testing hop fertility.”

Soil testing labs

Comprehensive soil health testing labs

Stay connected

For more information on hop production, visit the MSU Extension Hops website. Also, Michigan State University Extension is hosting a series of interactive Hop Chat Zoom meetings this 2021 season to allow easy communication between producers and MSU faculty. These informal weekly sessions run every Wednesday at noon from May 4 through Sept. 7 and include crop and pest updates from MSU Extension’s Rob Sirrine and Erin Lizotte. In addition, MSU faculty will drop in to address timely issues and provide research project updates. Bring your field notes, too! We want to hear what’s going on in your hopyard. Registration is free but required. Sessions will not be recorded. Register here!

This material is based upon work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2017-70006-27175. 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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