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Fruit update – June 18, 2024

Madeline Wimmer- UMN Fruit Production Extension Educator

This fruit update contains information about…
  • Grapes- Growth stage, downy mildew symptoms, and second generation phylloxera issues.
  • Honeyberries/haskap- General information, and Blue Fruit Farm field day with fresh honeyberry tasting panel.
  • Blueberries- growth stage.
  • Black currants- sawfly management.
  • LINK FIXED: Minnesota Department of Agriculture IPM Fruit Update sign up form. 


Image: Grapevine cultivar Madeleine Angevine in bloom at the UMN Horticulture Research Center (Zone 5a; photo taken by John Thull UMN HRC Vineyard Manager.)

Downy mildew

Images: 1, 2) Grape upper leaves showing symptoms of downy mildew (Plasmopara viticola) infection and 3, 4) grape leaf undersides showing downy mildew sporulation. Photos taken at the UMN Horticulture Research Center (Zone 5a) by John Thull, UMN HRC Vineyard Manager.)

Downy mildew (Plamopara viticola) is one grape fungal pest that thrives in highly humid environments. It can infect both grapevine foliage and fruit clusters, in which fruit clusters become more resistant as they continue to develop. After leaf infections occur, secondary infection can result from spores dispersed through wind and rain splash.

When scouting for downy mildew infections on leaves, look for classic “oil spot” symptoms that look slightly yellow with unclear margins on the topside of leaves and then flip symptomatic leaves over to see the underside sporulation present. As mentioned in updates from previous weeks, the rainy growing season we’ve been experiencing has presented challenges for growers by decreasing the number of opportunities when pesticide application can be done as well as the efficacy of its adherence. To learn more about using adjuvants known as “stickers'' that can help with fungicide adherence to foliage, refer to “Fruit update - June 6, 2024: Note on applying fungicides during raining growing seasons.” For more information on appropriate fungicides for downy mildew management, refer to the grape section of the Midwest Fruit Pest Management guide, beginning on page 155.

Grape phylloxera

Images: 1-3) Advanced grape phylloxera (Phylloxera viticola) infection on grape leaves. Photos taken at the UMN Horticulture Research Center (Zone 5a) by John Thull, UMN HRC Vineyard Manager.)

I introduced grape phylloxera (Phylloxera viticola) as a major grape insect pest in the grape section of, “Fruit update - May 15, 2024.” The above photos show what can happen when early management is missed and grape phylloxera begins to get out of control. However, even these photo examples are somewhat mild compared to very extreme cases in which infection is severe to the point of inhibiting leaves from unfolding, which also drastically impacts photosynthesis. Whether or not photosynthesis is impacted by the current state of phylloxera infestation, it is still a good idea to manage vineyard populations and mitigate future outbreaks. For more information about developing a grape phylloxera management plant, refer to the Midwest Fruit Pest Management guide, beginning on page 154.


Images: 1) Honeyberries/haskap tasting presented at the Organic Fruit Grower’s Association field day at Blue Fruit Farm (Zone 5a) to test consumer flavor preferences; results from this tasting were added to the app, Seed Linked. 2) Nearly ripe honeyberries/haskap.

Honeyberries, also known as haskap, are considered an emerging crop in the Upper Midwest. Most of the research and cultivar development of honeyberries has been done at the University of Saskatchewan, which offers a rich library of resources to inform honeyberry growers. Honeyberry plants are unique in that they tend to bloom early and be one of the first fruit crops available for harvest. They also can tolerate extreme winter temperatures and are one of a few crops that can thrive in regions as cold as USDA hardiness zone 2. At this point in the growing season, most honeyberries have finished or are at the tail end of harvest.

The University of Wisconsin (UW) Extension’s emerging crops team has also been developing resources related to the latest honeyberry research, news, and information. Last week, the Organic Fruit Growers Association put on a grower field day in partnership with UW Extension to learn more about honeyberries and small fruit crops at Blue Fruit Farm, which was followed by a honeyberry tasting session. This event was open to fruit growers and provided a valuable opportunity to learn directly from growers' experiences in honeyberry production.

Images: Photo and flavor profile results for honeyberry cultivar Boreal Beauty. Photo and chart originate from the Seed Linked website, which provides information to growers about cultivar production knowledge and consumer perception preferences.

What do honeyberries taste like?
Due to their blue fruit color, many growers and consumers who have yet to try a honeyberry might guess that they taste similar to a blueberry, but the two fruits taste very different. Honeyberries tend to be sweet and tart, and exhibit complex, deep flavor profiles. Similar to how growth habits and bloom times vary in honeyberry cultivars, not all honeyberries taste the same. They vary in size, texture, sweetness, acidity, and overall flavor profiles and complexity. This is why the software program Seed Linked has made an effort to collect consumer perception experiences related to eating honeyberry cultivars to inform growers and positively influence grower cultivar selection. Seed Linked also provides fruit production knowledge for growers based on input from plant breeders and other growers.

Allowing berries to fully ripen will also contribute to their flavor profile. Growers can use a refractometer to measure brix, or soluble solids levels in their honeyberries in combination with taste testing, color, and ease of fruit separation from the shrub to know when to harvest. Most honeyberries are ripe enough to harvest between 16-20 brix.

Culinary uses for honeyberries:

Image: A waffle drizzled with honeyberry sauce and side of maple syrup. Sauce created by simmering frozen honey berry fruits with a small amount of added sugar, followed by blending and straining into a sauce bottle for precision sauce application.

Honeyberries can be eaten fresh, frozen and used in smoothies, and incorporated into other value added goods like sauces, jams, and additions to ciders and mead. 


Image: Hybrid blueberries in the “late green” blueberry growth stage at Blue Fruit Farm near Winona, Minnesota (Zone 5a.)

Blueberries are in the “late green” growth stage and will soon begin transitioning into the “fruit coloring” in which the oldest, largest berry will be the first to change color. At the fruit coloring stage, the berries will also begin to soften and continue to expand until they are ready for harvest.

Sawflies and black currants

Image: A black currant plant that has been harmed by sawflies (either Nematus ribesii or Pristophora sp.), showing heavy defoliation and early fruit ripening.

Oftentimes direct pests that feed on fruits seem to be more concerning than indirect pests that may affect foliage or other plant anatomy. In the case of a severe defoliation from an insect pest like sawflies, such damage can majorly impact plant health, and a plant’s ability to overwinter and thrive in future growing seasons.

The currant sawfly, also known as the imported currant worm, is a major insect pest of currants. The adults lay their eggs on the underside of currant leaves during the spring and the leaf damage is caused by larvae, which emerge from the eggs and rapidly consume currant leaves. Growers can scout for sausage-shaped eggs to detect their presence and then look for early defoliation symptoms, which look like small brown patches on foliage.

Currant sawflies are not in the lepidopteran family like moths are, which means their larvae are not caterpillars and they are not susceptible to Bt applications. The Pacific Northwest Pest Management Handbooks provides more information related to chemical management options for currant sawfly; however, knowing which development phase populations are in is key to their management. Oftentimes, when severe damage has been detected, many larvae are already beginning to pupate and, after their emergence, a second generation can continue to pose issues for growers. Currant sawflies can go as many as three generations per growing season.

Growers who are looking for more general information related to currant production can refer to the Minnesota Institute for Sustainable Agriculture (MISA) publication, “Perennial Fruit: Currants,” as well as the “Black currant grower’s guide for the Midwestern US,” published by the Savannah Institute.

LINK FIXED: Minnesota Department of Agriculture IPM Fruit Update sign-up form.

For those who are not familiar, the MDA has been keeping reports on insect pest trapping incidences for apples and putting out an IPM newsletter for years. The newsletter complements information presented in the UMN fruit updates and has been valued by many Minnesota fruit growers.

If you are interested in subscribing to the MDA IPM Fruit Update series, follow the link below to sign up.

MDA IPM Fruit Update sign up form.  


The University of Minnesota Extension fruit production program would like to extend a thank-you to the growers who make these reports possible.

Non-credited photos in these publications were taken by the author, Madeline Kay Wimmer, M.S.

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