Michigan hop crop report for the week of June 14, 2021

Hop nutrient and water demand remains high across the state.

hopyard
West central Michigan hopyard on June 11, 2021. Photo by Erin Lizotte, MSU Extension.

Weather

We had an unusually warm week (8-12 degrees Fahrenheit higher than average). With our higher-than-normal temperatures, we are about a week ahead in terms of growing degree days (GDD). Over the last week, there was precipitation across the state, but it was widely scattered. Some areas of the state received up to 2 inches, but most areas received less, especially near Lake Michigan. Twenty-nine percent of Michigan is under D2 severe drought, with the Upper Peninsula being the exception.

U.S. Drought Monitor

We will see fair, dry and seasonably cool temperatures across most of the state Tuesday and Wednesday before becoming warmer on Thursday. This weekend will likely be fair, dry and cool. The best chance for rain we have seen in several weeks will occur late Thursday into Friday afternoon. Overnight Sunday into Monday we may also see some precipitation.

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

june 14 hop rainfall
Accumulated rainfall summary for hop producing areas of Michigan on June 14, 2021, as compared to the five-year average. Data from MSU Enviroweather.
june 14 hop gdd
Accumulated degree day (base 50 F) summary for hop producing areas of Michigan on June 14, 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

Plants are at or close to the wire. Weed burnback is in progress. Growers are actively fertilizing and treating for leafhoppers. The weather has cooled off a bit with overnight lows in the 50s.

Hops hitting the wire.
Hops hitting the wire. Southeast Michigan. June 14, 2021. Photo by Rose Stahl

Southwest Michigan

Hops are 12-15 feet. Corn borer pressure has been pretty low since the last treatment. Mite pressure has been stable and doesn’t seem to be increasing. Growers are actively fertigating and conducting SAP analysis to determine plant nutrient needs. Some growers have foliar applied micronutrients. Laterals are pushing across the board and weed burnback will begin today.

Cascade hops
Cascade hops in southwest Michigan. Crushing it. June 14, 2021. Photo by Rick Kawalski

East central Michigan

Hop height varies by cultivar from 10-12 feet. Spider mites are active with the heat. Burnback is expected to happen near the end of the week. Everything is progressing well.

West central Michigan

Hops are 10-15 feet. Potato leafhopper is under control in treated yards. Some webbing from twospotted spider mites is visible on the underside of leaves from the lower foliage mat.

Northeast Michigan

Most plants are 10-12 feet tall with a few approaching the top wire. Fertigation and irrigation are in full swing. Hops are averaging 6 inches of growth per day at a minimum. Growers hilled for the final time of the season last week. Dry conditions persist.

Hops
Hops growing at least 6 inches per day in northeast Michigan. June 14, 2021. Photo by Andrew Walawender

Northwest Michigan

No update is available this week.

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

Basal spikes and lateral infections of downy mildew have been seen in southwest Michigan for the past few weeks. Downy mildew symptoms will likely continue to develop into secondary downy mildew on lateral shoots if left uncontrolled. Most growers have made 1-2 chemical application 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. 

Foliar symptoms of powdery mildew
Foliar symptoms of powdery mildew from July 2020 in southwest Michigan. Photo by Timothy Miles, MSU.

Insects

Twospotted spider mite activity is building around the state and growers finding mites during scouting should be treating. 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 numbers have continued to build in untreated yards. 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. 

Growers may also be seeing European rose chafer or will likely see them emerge soon. Rose chafers are considered a generalist pest and affect many crops, particularly those found on or near sandy soils or grassy areas conducive to grub development. The adult beetles feed heavily on foliage and blossom parts of numerous horticultural crops in Michigan and can cause significant damage to hop plants, particularly young plants with limited leaf area. Rose chafer skeletonize leaf tissue, giving them a fine lace-like appearance. Rose chafer cause simple mechanical damage so growers should consider that established plants can sustain a significant amount of leaf feeding from rose chafer with no negative implications to the plant or crop. Young plants with limited leaf area may require more aggressive management.

Chafer activity has typically subsided by the time burrs are present so flower damage that could have yield implications is not an issue. For more information, visit the European rose chafer page and refer to the Michigan Hop Management Guide.

Rose chafers
European rose chafer mating and feeding on hop foliage. Photo by Erin Lizotte, MSU Extension.

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

Plant-tissue 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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