MSU Extension Grapes

Regional weather and seasonal progress

Seven-day forecasts for Michigan grape regions are as follows:

• Southwest Michigan: Benton Harbor | Fennville | Lawton | Watervliet
• Northwest Michigan: Old Mission | Suttons Bay| Traverse City | Leland | Northport
• Tip of the Mitt AVA: Petoskey | Harbor Springs | Charlevoix | East Jordan

Weekly in-season weather updates are provided to the MSU Extension fruit team by Jeff Andresen, PhD, MSU agricultural meteorologist. These reports offer timely insights into weather conditions affecting fruit production across Michigan. You can watch recordings of these agricultural weather outlooks.

Growing degree day (GDD) report

You can track vine development using the MSU Enviroweather Growing Degree Day Map. Visit the Enviroweather site to find your nearest weather station, create a free account, and monitor GDDs daily.

Biweekly GDD summary (base 50 degrees Fahrenheit)

The following table summarizes current GDD accumulation, last week's totals and the biweekly increase for each monitored location across Michigan:

Vine development

Southwest and southeast Michigan

Grape bloom is finishing. Some early hybrids are at Buckshot Berry. Vinifera wine grapes are between immediate prebloom and completing bloom, depending on variety and location. Juice grape bloom is almost complete in locations not damaged by spring frosts/freezes. In vineyards damaged by the spring frosts, secondaries are now blooming. A line of storms moved through the region early evening on June 16. Several reports of hail in multiple grape production locations have resulted in damage. The extent of damage is still being assessed, but additional fungicide applications are recommended while the vines recover in these locations.

In southeast Michigan, most grape cultivars are at fruit set, including juice grapes, table grapes, and hybrid wine grapes. Later cultivars and vines in cooler parts of the region are still in bloom.

Northwest Michigan

Across northwest Michigan, most Vitis vinifera cultivars are experiencing a period of rapid shoot growth, with lengths now averaging 8–10 inches. Given current environmental conditions, we anticipate the onset of bloom within the next seven to 10 days. Growers should remain vigilant as we approach this critical phenological stage, particularly regarding bloom-time disease management.

Tip of the Mitt

Hybrid cultivars have reached the 10- to 16-inch shoot stage, with clusters in the immediate pre-bloom phase. Meanwhile, Vitis vinifera cultivars are generally at the 4- to 8-inch growth stage, though some advanced shoots are pushing into the 10- to 16-inch range. Wild vines are currently in the early stages of bloom. Regarding pest and disease management, rose chafers have been observed in select vineyards, but Phomopsis and black rot pressure has fortunately remained light so far.

For reference, see MSU Extension’s grape growth stages chart.

Viticulture

Optimizing canopy architecture and maintaining robust soil health are foundational to sustainable vineyard performance, high fruit quality, and disease mitigation. The following is a consolidated guide to these essential early- and mid-season viticulture practices.

Early-season canopy and crop management

Timely interventions dictate the structural balance of the vine. In warmer regions, these practices begin at 10–15 inches of shoot growth, while cooler northern sites should prepare to execute them as pre-bloom development progresses.

• Shoot thinning: Removing weak, excess or non-count shoots establishes optimal canopy density. This improves light interception, enhances airflow and supports uniform cluster development. Read more.
• Shoot positioning: Promptly securing shoots vertically prevents tangling and guarantees effective spray penetration.
• Crop load assessment: While major thinning typically occurs post-fruit set, early removal of clearly excessive or poorly positioned clusters reduces resource competition and improves fruit set consistency.
• Pre-bloom leaf removal: In high-vigor sites, targeted early leaf removal in the fruiting zone improves the microclimate and reduces future disease pressure, particularly for compact-clustered cultivars.

Cool-climate optimization

Growers in regions with compressed growing seasons, such as northwest Michigan, must use strategic interventions to maximize ripening and counter harvest-season rot complexes.

Early hedging

Cutting shoots shortly after they surpass the top wire redirects vine energy away from vegetative expansion and toward fruit development. Research from Michigan State University (MSU) indicates this practice preserves highly photosynthetically active leaves and promotes beneficial lateral growth that drives late-summer ripening. Timing is critical: hedging too early can trigger an overly dense canopy, especially in vigorous cultivars.

Cluster-zone leaf removal and mechanization

Managing the microclimate directly around the fruit is the most impactful technique for protecting tight-clustered varieties like Pinot Noir and Riesling.

To bolster economic sustainability, the industry is transitioning to mechanical systems like the Collard compressed-air leaf remover. Beyond stripping leaves, targeted bursts of air blow out necrotic floral tissue. This critical secondary benefit eliminates the nutrient base where latent Botrytis spores typically overwinter before spreading post-veraison.

Recommended reading from MSU Extension:

• Early hedging for healthier canopies and better ripening in cool climates
• Cutting to the core: Michigan State research leads a canopy innovation in cool-climate viticulture

Soil health

A resilient soil structure ensures consistent vine performance and nutrient use efficiency under volatile weather conditions.

• Cover cropping: Row-middle cover crops reduce surface erosion, build soil organic matter, and stimulate beneficial microbial activity.
• Organic amendments: Incorporating compost improves the soil's water-holding capacity and establishes a slow-release nutrient reservoir throughout the growing season.
• Compaction prevention: Avoiding heavy machinery traffic on wet soils preserves soil aeration and protects root integrity. This is especially vital during periods of rapid root growth and peak nutrient uptake.

Pest management

Diseases

Fungicide programs should prioritize materials with strong protectant and systemic activity, while rotating modes of action to manage resistance. Products in FRAC groups 3 (DMIs) and 11 (QoIs), often used in premixes, remain key options for powdery mildew and black rot, while multi-site protectants such as captan (M4) or mancozeb (M3) provide additional coverage and help reduce resistance risk.

For downy mildew, materials in FRAC groups 40, 45, 21 and 11, as well as phosphorous acid products, are effective choices when conditions favor infection. Careful selection and rotation of these chemistries, combined with thorough coverage during bloom, are essential to protect developing clusters and limit early-season disease establishment.

Insect pests

Insect activity is picking up with rose chafers, potato leafhoppers, leafrollers and berry moth found in vineyards in the last week. Berry moth traps indicated high activity of male moths across southern Michigan (Photo 4). Monitoring clusters in southwest Michigan recently identified some larvae that were berry moth larvae and a few that were leafroller larvae. Feeding on young clusters has limited effect on later yield, but continued scouting through the next few weeks will indicate if egglaying and larval infestation is starting in your specific sites.

Insect control in the post-bloom period can target a range of insects found during scouting if the right product selection is made. Consult MSU Extension publication E-154 for the available insecticide options and their ratings against different pests.

Grape tumid gallmaker symptoms were observed in a few vineyards this week (Photo 5). This can be isolated to a few vines, where infested leaves and clusters can be removed and destroyed. Widespread infestation may require treatment to protect leaves and clusters. Assail is one effective option that can protect from further infestation. However, application at first sighting of the pest’s symptoms will be best for control, so plan ahead for affected areas in 2027.

Weeds

Early-season weed management is important in vineyards to reduce competition for water, nutrients and light, especially in young or newly planted blocks. Maintaining a relatively clean undervine strip during early shoot growth can support vine establishment, improve nutrient uptake and reduce competition during a critical period of vine development.

Scout vineyard floors now to identify winter annuals, emerged summer annuals and perennial weeds. Winter annual weeds may already be flowering or setting seed, so timely control can help reduce seedbank inputs. Summer annual weeds such as pigweed, lambsquarters, foxtails and annual grasses will continue emerging as soils warm.

Several herbicide options are listed in the 2026 Michigan Fruit Management Guide. In established vineyards, the first step is to determine whether weeds have already emerged.

If the vineyard floor is clean, a residual herbicide such as Chateau, Prowl H2O, Surflan, Princep, Karmex, Zeus XC, Zeus Prime XC or Alion may be used, depending on vine age, soil type and label restrictions.

If weeds are already present, include a labeled burndown herbicide such as glufosinate, paraquat, glyphosate, Aim or Venue with the residual product. Examples include glufosinate + Chateau, glyphosate + Prowl H2O, glufosinate + Zeus XC or Zeus Prime XC, glyphosate + Princep, or Karmex + Prowl H2O or Surflan, where labeled and appropriate. Apply Zeus XC and Zeus Prime XC to weed-free soil or with a burndown partner if weeds are present. They should not be tank-mixed with Chateau.

For grass-only problems, Fusilade DX, Poast or Assure II may be used when grasses are actively growing. Organic growers may consider caprylic plus capric acid products where labeled.

Apply all postemergence herbicides as directed sprays to the vineyard floor and avoid contact with green shoots, leaves, green bark, suckers, and young vines. Always follow the label for crop age restrictions, rates, adjuvants, preharvest intervals, and tank-mix compatibility. Rotate herbicide sites of action and integrate mowing, cultivation, cover crops, or other nonchemical tactics to reduce herbicide-resistance risk.

Scouting and recordkeeping tools

The growing season is an ideal time to implement efficient scouting, spray planning and recordkeeping systems. The Sustainable Agriculture Management (SAM) Tool, developed for Michigan grape growers, provides a user-friendly platform to support spray and non-spray task management.

Recent updates have improved functionality, including streamlined task planning, easier editing and duplication, improved activity tracking and enhanced communication features. The tool also offers a redesigned mobile interface and supports grower-participatory research.

The SAM Tool is free to use and suitable for vineyards of all sizes. Growers are encouraged to incorporate it into their operations to improve efficiency, organization and decision-making throughout the season.

Personalized onboarding and support are available through the SAM Tool team. For assistance or to schedule a walkthrough, visit the SAM Tool website or contact the team directly at SustainableAg@anr.msu.edu.

Frequently asked question: Why does a completed spray task still appear as "Yet to Be Completed"?

This may occur when the manager creates a "Both" task (Mixing/Loading + Spraying) for the same worker.

Although the worker sees a single task, SAM Tool processes it as two separate tasks. After completing the Mixing/Loading portion, the worker must tap Completion. A new Spray task will then appear in the task list.

The worker must select the Spray task, tap Start, and then tap Completion again after spraying is finished. Otherwise, the spray portion will remain marked as incomplete.

If you continue to experience this issue, please contact the SAM Tool support team and provide the task details.

Events and announcements

We are pleased to share the upcoming schedule for this season’s P45 Third Thursday events. These sessions are designed to provide timely, field-based insights and practical demonstrations aligned with current vineyard conditions. More details will be shared as the season progresses. We encourage growers and industry members to mark their calendars and plan to attend.

June 18 – Mawby Vineyard | Compost Tea

Join us at Mawby Vineyard for a discussion on compost tea applications and their role in soil health and vineyard management. This session will focus on practical considerations, potential benefits and integration into existing vineyard programs.

July 23 – Northwest Michigan Horticulture Research Center | Sap Analysis

This session will highlight using sap analysis as an in-season tool for monitoring vine nutrient status. Discussion will include interpretation of results and how to incorporate sap data into nutrient management decisions during the growing season.

August 6 – Northwest Michigan Horticulture Research Center | Spray Efficacy Workshop

This workshop will focus on improving spray efficacy in vineyard systems. Timothy Miles, PhD, and Mike Reinke, PhD, will lead discussions on optimizing spray programs, coverage and disease control. The session will also feature demonstrations of drone-based sprayers and newly available autonomous spray technologies. Additional expertise from an invited out-of-state speaker is anticipated.

More details will be shared as the season progresses. We encourage growers and industry members to mark their calendars and plan to attend.

37th annual Michigan Viticulture Field Day and Enology Experience

Registration is open for the 2026 Michigan Viticulture Field Day and Enology Experience.

The Michigan Viticulture Field Day program will highlight new technologies for grape growers with demonstrations of autonomous and smart spraying systems and electric weeders. Sustainable viticulture practices will also be showcased, such as non-chemical weed management strategies, sheep grazing and the new MSU regenerative and organic demonstration vineyards.

The Michigan Enology Experience will include discussions on innovative winemaking technology, a hands-on tasting workshop and guided tastings of experimental wines from Lake Michigan Vintners and other wineries from southwest Michigan. The day will conclude with a blind comparative wine tasting pitting Lake Michigan Shore wines against international standards.

Register for the 37th Annual Michigan Viticulture Field Day and Michigan Enology Experience

2026 Dirt to Glass Conference

Registration is open for the fifth annual Dirt to Glass Conference, taking place Aug. 20–21 in Traverse City, Michigan. Early bird pricing is available for a limited number of registrations.

Register for the 2026 Dirt to Glass Conference

The program features 23 speakers covering vineyard management, winemaking, soil science, vine physiology and wine evaluation, combining Michigan expertise with national and international perspectives. The conference is designed as a working forum with moderated panel discussions focused on practical, vineyard-to-winery decision-making.

Highlighted speakers include:

• Nick Dokoozlian (E. and J. Gallo) – vineyard-to-wine quality benchmarks
• Jacopo Miolo (Simonit and Sirch) – pruning and vine longevity
• Tom Plocher – disease-resistant varieties
• Madeline Triffon – sensory evaluation
• Bruno Basso (MSU) – soil health and site-specific management

The program also features applied sessions on scouting, soil biology and vineyard establishment.

A key focus this year includes collaboration with E. and J. Gallo to pair sensory evaluation of Michigan wines with advanced chemical analysis, supporting improved quality assessment and production strategies.

The conference includes a two-day format:

• Day one (Aug. 20): technical sessions, panel discussions and guided tastings at the Cathedral Barn at Historic Barns Park
• Day two (Aug. 21): field tours of vineyards and wineries with visiting experts

Space is limited. Day two participation requires day one registration.

This work is supported by the Crop Protection and Pest Management Program [grant no 2024-70006-43569] from the USDA National Institute of Food and Agriculture. 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.