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2017-18 Michigan Grape Growing Seasons: A Year In Reflection And a Year in Projection
By Thomas Todaro
 
Michigan grape producers overcame the seasonal challenges in 2017. What are the upgrades to the Michigan State University research and Extension capabilities in 2018?
 
A year in reflection: 2017 growing season
 
Each season in 2017 brought challenges for Michigan grape producers. Spring frost in early May damaged 3-to-6-inch shoots and flower clusters of juice and wine grapes in southwest Michigan, while wine grapes grown in the northwest were still in early bud swell (Eichhorn-Lorenz phenological stage 02), and thus not as susceptible to frost damage. However, the northwest had their own spring challenge of apparent reduced fruit set induced by cool, wet conditions.
 
Thirty-six inches of snow insulate the trunks and cordons of grapevines grown on Leelanau Peninsula on Jan. 4, 2018. 
 
Spring and summer rainfall, measured from April 1 through Oct. 31, in both southwest (28.0 inches) and northwest (22.0 inches) Michigan, was 5 and 2 inches greater than their five-year averages, respectively. Similarly, the hours of rainfall in southwest (384 hours) and northwest (398 hours) Michigan were 52 and 43 hours greater than their respective five-year averages.
 
Specifically, grapevines grown in the two predominant American Viticulture Areas in the northwest—Leelanau Peninsula and Old Mission Peninsula—accumulated a relatively low number of growing degree-days, which is a measure of heat accumulation during the growing season. In fact, from April 1 April through Aug. 31, the American Viticulture Areas mentioned accumulated fewer growing degree-days than their five-year averages. This increased amount and time of rainfall coupled with a relatively cool growing season resulted in grape producers spending more time in the vineyard managing the vigorous rain-induced growth, and defending the grapes and leaves against fungal pathogens that thrive in moist and cool conditions.
 
Although the environment presented challenges, it also gave the grape producer’s fruit enough dry heat during the September and October months to reach maturity with clean fruit, and normal to above average tonnage per acre reported at harvest. This is supported by the late-season growing degree-day accumulation, measured from Sept. 1 through Oct. 31, in southwest (704 growing degree-days) and northwest (647 growing degree-days) Michigan, which was greater than their five-year averages, respectively. A real world impact of this late-season dry heat was that many grape producers in the northwest reported that Pinot noir, a “delicate,” thin-skinned red grape susceptible to cluster deterioration, was allowed to hang and ripen much longer than usual.
 
In the northwest, 2017 had a significantly shorter growing season (fewer frost-free days) by roughly two to three weeks, and earlier and colder minimum temperatures going into the winter than in 2016, resulting in a relatively short or non-existent post-harvest foliated period. It was reported that some grape producers had clusters on leafless vines, an occurrence that can have negative effects on the fruit and wood.
 
There have been no reports of significant bud and cane damage during the 2017-2018 winter in the northwest or southwest, as the lowest temperature to date recorded at the Northwest Michigan Horticulture Research Center was -0.1 degrees Fahrenheit on Jan. 5, 2018. However, the lowest temperature to date recorded at the Southwest Michigan Research and Extension Center was -7.6 F on Jan. 2, 2018, which is low enough to cause significant primary bud damage to cold tender Vitis vinifera grapevines in the southwest region. We will not know the severity of cold damage and injury until samples are assessed.
 
Again, each season brought its own list of challenges and each trial was met and overcome by Michigan grape producers. Specifically, in the northwest, there were conditions during bloom that were not conducive to a strong berry-set, but many have found normal to above average tonnage and quality at harvest. The cool and wet summer induced more rapid shoot growth, increased disease pressure and slowed grape ripening. However, the dry heat in September and first half of October yielded some exceptional fruit, so most varieties developed well and may produce exemplary wines. Very exciting when you consider that in mid-August, a mediocre season was expected.
 
A year in projection: 2018 growing season
 
In northwest Michigan, research and Extension efforts of 2018 will have two main objectives: 1) Successfully establish the new research vineyard, and 2) assist commercial grape producers by implementing research-based practices to enhance fruit maturity and quality and reduce insect and disease pressure in a sustainable and economical way.
 
We will plant at least one acre of wine grapes at the Northwest Michigan Horticulture Research Center in late May through early June. This new planting will be comprised of core cultivars: Cabernet Franc, Chardonnay, Pinot Blanc, Pinot Gris, Pinot Noir and Riesling. The purpose of this planting will be to monitor and subject these cultivars to protocols to enhance the quality and quantity in the grapes and ultimately in the wine. In other words, northwest Michigan has proven that it can produce excellent wines made from these popular cultivars, but more research-based information is needed to consistently ripen fruit annually to promote and expand the industry.
 
We will be purchasing grape maturity equipment to measure basic juice composition in multiple regions and vineyards in the northwest. With grant funds, we will also hire a summer research technician to assist in the early care of the research vineyard, collect fruit maturity and pest data—this information will be communicated back to the growers so they can make sound viticultural decisions. Michigan State University Extension efforts will work in tandem with research already underway by invasive insect pest and viticulture experts at the Northwest Michigan Horticulture Research Center and Michigan State University.
 
We are bringing fruit maturity technology and working with Michigan State University experts to bring the very best viticulture research and Extension to promote and improve the vibrant grape and wine industry of northwest Michigan!