Michigan State University Extension released its latest grape scouting report on May 5, summarizing vineyard conditions, pest and disease activity, and upcoming events for growers across Michigan.
The bi-weekly report aims to keep grape growers informed about seasonal progress and practical management strategies. The update highlights slow vine development in northern Michigan due to cool weather, while southern regions have experienced frost events causing damage and loss of primary shoots. Early-season disease risk is rising in the south, with protective programs recommended.
According to the report, “Northern Michigan vine development is progressing slowly due to recent cool conditions, as grapes remain dormant to pre-bud swell.” It also notes that “Southern Michigan has seen several frost and freeze events resulting in damage and loss of primary shoots in many locations.” The team advises that insect activity has begun—particularly grape berry moths—and recommends monitoring young vineyards closely. A critical management window for early disease protection, shoot thinning, and nutrient planning is underway.
The report provides detailed growing degree day (GDD) summaries by region. In southwest Michigan, GDD accumulation stands at 327.4 (base 50 F), with a forecast of continued slow growth due to persistent cool temperatures. Northwest Michigan remains behind typical development schedules; most Vitis vinifera cultivars are still dormant or just beginning sap flow. In the Tip of the Mitt region, hybrids may soon show signs of bud swell as temperatures rise.
MSU Extension offers ongoing support through resources such as weather outlook recordings from Jeff Andresen, PhD; guidance on nutrient management based on soil tests; pest management recommendations for diseases like phomopsis cane spot and black rot; updates on insect pests including flea beetles; and weed control strategies for young vineyards.
Upcoming events include P45 Third Thursday sessions focused on compost tea applications (June 18), sap analysis (July 16), spray efficacy workshops (August 6), the annual Viticulture Field Day featuring technology demonstrations and sustainable practices, as well as the Dirt to Glass Conference scheduled for August 20–21 in Traverse City with speakers covering vineyard management through wine evaluation.
Michigan State University Extension Agriculture addresses challenges in food systems, health outcomes, environmental stewardship through education initiatives statewide—including facilities such as research centers and farms—and maintains collaborative research programs across all counties according to the official website.
This work is supported by a grant from the USDA National Institute of Food and Agriculture’s Crop Protection and Pest Management Program.
