Michigan hop crop report for the week of May 10, 2021

Hop growth is in a holding pattern as cool, dry weather persists across most of the state.

Healthy hop shoots.
Photo 1. Healthy hop shoots on May 8, 2021, in west central Michigan. Photo by Rob Sirrine, MSU Extension.

Weather

Currently, moderate drought conditions persist for most of the Lower Peninsula. Temperatures have been cooler than normal over the past week, although it appears as though temperatures will gradually increase close to normal over the next week.

Temperatures were 2-3 degrees Fahrenheit below normal in northern Michigan and 2-4 F above normal in southeast Michigan. There was a growing degree day GDD (GDD) surplus of seven to 10 days in some southern Michigan growing areas, a smaller surplus in northern Michigan and GDD were near average in the Upper Peninsula.

Some precipitation fell in northern Michigan over the last few days, whereas southern and central Michigan continue to experience a moisture deficit.

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

Graph

Graph

Stage of production/physiology

Because of the cool weather over the past week, not much has changed from the May 3, 2021 report. Hops across Michigan are in Principal Growth Stage 1: Leaf Development (see chart below). Growers continue to string or have completed stringing. Irrigation systems are coming back on-line. Most growers who prune did so across the state between April 18-25, though some may have pruned earlier due to the unseasonably warm temperatures in early April. Unpruned yards in west central Michigan have up to 4 feet of growth.

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

Southwest

Several yards are fully strung (Photo 2). Several yards that were treated with herbicides have started to push new growth (Photo 3).

Strung hopyard.
Photo 2. Strung hopyard in southwest Michigan. Photo by Tim Miles, MSU.

East central

Preemergent was on March 31. Weed badger mechanical prune on some took place on April 20 (early varieties), April 25 (mid) and April 30 (late). Mechanical pruning is not ideal but more effective than chemical prune. Chinook cut two times this year. Will train in about 20 days (May 25). Tying 675 strings per hour. Four acres of 17.5 left to string.

No fungicide spray as of May 5, but likely was applied May 6 or soon. Training on early varieties will begin in around May 15. Preemergent seemed to do well, but grass and thistle always persist. Spot spraying with herbicide will be done prior to discing or opening soil and spreading weeds. Granular application of about one-third phosphorus and potassium as well as some gypsum and calcium. Shoots are anywhere from just cut to 14 inches (centennial).

Northwest

Many growers have focused on getting irrigation systems up and running. Like other areas of the state, they are also planning to spray susceptible cultivars at the end of this week and other cultivars early next week.

Northeast

Northeast Michigan is in a holding pattern due to the cool weather. Growers will finish stringing this week. Of note, stringing has been difficult with windy, cool conditions.

Weeds

With increased precipitation, grass weeds are taking off and need to be treated when small for optimal control. 

New hop growth.
Photo 3. New growth following herbicide treatments is beginning to push. Photo by Tim Miles, MSU.

Diseases

Downy mildew spikes were observed in southwest Michigan on May 11 (Photo 4). Some growers are considering making a chemical application. Once herbicide burndowns are completed, consider a drench or banding treatment for downy mildew using effective chemistries (Ridomil Gold SL, FRAC 4). Other effective foliar fungicides include products in FRAC codes 4, 11, 21, 40, 43, 45 and 49. See the Michigan State University 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.

Due to the long preharvest interval (PHI), growers might want to utilize a Ridomil/FRAC 4 drench. When considering a drench application, the goal is to get the Ridomil down to the roots so it can be taken up by the plant's other tissues. If it is only applied to the above-ground parts, it will not move down because of the chemical nature of this product. Moist soil can help get the product dispersed around the root zone but avoid applications immediately before very heavy rain, or you risk the fungicide being washed below the root zone, where the plant cannot take it up.

Downy mildew spike on hop.
Photo 4. Downy mildew spike observed May 11, 2021, in southwest Michigan on 'Cashmere' hops. Photo by Tim Miles, MSU.

Insects

No significant insect pest observations this week.

Nematodes

Recently, the MSU Applied Nematology Laboratory determined that young hop plants infected with two plant-parasitic nematodes can result in significant damage to the plant. Infection by the hop cyst nematode and the northern root-knot nematode reduced bine growth by 40.4% and 69.4%, respectively, when compared to control plants. So far, the hop cyst nematode has only been documented once in Michigan. However, in a recent grower questionnaire, 15 of 16 participating Michigan growers indicated they have never sampled their yards for nematode pressure.

For this reason, the MSU Applied Nematology Laboratory will conduct a statewide survey of hopyards this month in an attempt to document the most encountered plant-parasitic nematodes in Michigan hopyards and monitor hop cyst distribution. After this information is collected, we will further investigate how infestation by the most encountered pests potentially impacts hop plant growth.  

Growers are encouraged to submit soil sampling to MSU Plant & Pest Diagnostics prior to planting new rhizomes, especially if the hopyard was used to grow hops previously. Obtaining clean plant material is also vital to reduce the spread of infected rhizomes to clean yards. Some species of cyst nematodes have the capability to lie dormant in fallow soils for over 10 years, so it is unlikely that crop rotation or leaving yards fallow for years will alleviate pressure from this pest. Because hop cyst nematode has no known method of control and populations can rise quickly under optimal conditions, prevention is the best course of action.

Fertility

Most growers using granular fertilizers have already applied them or are planning to apply them soon. As a reminder, please reference the Nutrient Management section (pages 22-26) of the Michigan Hop Management Guide for fertility recommendations. Also, 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.

Soil testing labs

Comprehensive soil health testing labs

Hopyard.
Photo 5. West central Michigan hopyard on May 8, 2021. Photo by Rob Sirrine, MSU Extension.

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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