Article written by Madeline Wimmer, UMN Extension Fruit Production Educator
Blueberries
Growth stage: Fruit harvest for early hybrid and highbush varieties
SWD updates and exclusion netting
Disease: Anthracnose fruit rot
Grapes
Japanese Beetle: First sighting of the year and the winsome fly parasitoid
Optimal timing for basal leaf and lateral shoot removal
Pears
Variety highlight: Summercrisp
Black currant
Growth stage: Ripening
Blueberries
Growth stage: Fruit harvest for early hybrid and highbush varieties
Images: Blueberries are coming into harvest season at farms in southern Minnesota, including Blue Fruit Farm, near Winona and Little Hill Berry Farm in Northfield. Here pictured Northland (left) and Polaris (right), both hybrid blueberry varieties.
We’re coming up on the start of harvest season for blueberries in southern Minnesota where both hybrid (half-high) and highbush blueberries are planted. Blueberry production in these regions often requires monitoring of the soil pH as soils in these regions tend to have higher pH and calcareous water that, when directly used for irrigation, can raise the soil pH after a number of years. While both types of blueberries can grow in Minnesota, hybrid ones tend to have hardier buds that are more suitable for overwintering, especially in northern regions.
When a diverse number of blueberry varieties are planted, the harvest season can be stretched for a longer period of time. Early producing varieties include Northland and Patriot (highbush) as well as Polaris (hybrid), whereas varieties like Nelson (highbush) tend to be more mid-season, and Elizabeth and Elliot (highbush) are late season producers.
The University of Minnesota has bred and released a number of hybrid varieties, which include Polaris, along with others like Northsky, Pink Popcorn, Superior, and St. Cloud. I had a chance to try Polaris this week while I was at Blue Fruit Farm, which may become a new favorite as the berries had a lower tartness and jammy flavor even though the berries were on average smaller than other varieties. For more information and listings of UMN varieties, visit the UMN Minnesota Hardy website.
SWD updates and exclusion netting
Images: Exclusion netting is one method to manage spotted wing drosophila (SWD) from blueberries and other fruit crops (left). A map provided by the Vegetable Disease and Insect Forecasting Network can give insight for SWD population pressure in various regions in the Upper Midwest (right).
Right now, spotted wing drosophila (SWD) populations are forecasted to be at lower levels in southern Minnesota, and very low for regions that are north of St. Cloud. SWD has a multitude of options for managing various crops, including blueberries. One of these methods is exclusion netting, which is covered in more detail in this week’s article below.
Article: Spotted Wing Drosophila (SWD) season updates and exclusion netting
Disease: Anthracnose fruit rot (ripe rot)
Images: Anthracnose fruit rot leads to berries shriveling up, which concentrates the sugars within the fruit.
Anthracnose fruit rot is a disease that can impact blueberries in Minnesota caused by a combination of two different fungal species Colletotrichum acutatum and Colletotrichum gloeosporiodes. The two species can overwinter on twigs and buds and can cause infections during prolonged wet conditions with warm temperatures around 77 F. One thing unique to this disease is that after the pathogen gets under the fruit surface, it can remain latent until the fruit matures, after which point it uses enzymes to break down the fruit tissues.
This particular infection situation likely was worsened when exclusion netting was placed over the blueberry shrubs while they were still wet. Improving air flow in general can be helpful to reducing prolonged periods of wetness, which can be done by pruning the canopy to decrease its density. Growers should also use drip irrigation instead of overhead irrigation.
For those who use fungicides in their management, applications typically begin at full bloom until harvest, but should only be used when needed. Additional practices that can help include frequent harvesting and keeping equipment clean when going from infected shrubs to non-infected shrubs. For farms that pick their own fruit, cooling the fruit down within two hours of harvest can help slow down infections.
Resources cited:
Anthracnose fruit rot (ripe rot) of blueberries (North Carolina State Extension)
Grapes
Japanese Beetle: First sighting of the year and the winsome fly parasitoid
Image: Japanese beetles have a wide host range and are a common pest of grape leaves in Minnesota and the Upper Midwest.
I spotted my first Japanese beetle for the year in SE Minnesota on Tuesday 06/30. Japanese beetles have been an invasive pest in Minnesota since the late 1960s and have increasingly become a pest in vineyards for the past 10-15 years. They have over 300 known host plants, commonly impacting the foliage and occasionally fruit for some crops like peaches and raspberries...
To read the full article and learn more about Japanese beetles, check out the article link below:
Article: Japanese Beetle: First sighting of the year and the winsome fly parasitoid
Basal leaf removal, or removing leaves to expose developing grape clusters to sunlight, is one of the simplest and quickest ways to improve fruit quality in climates where the growing season is short. This week’s article goes into the research and best practices for post-bloom leaf removal, and highlights more recent research done in Michigan on the practice of pre-bloom leaf removal, which can promote looser clusters as a result.
To learn more, check out the following article.
Article: Optimal timing for basal leaf and lateral shoot removal
Summercrisp is one of four cold-hardy pear varieties released in 1986 from the University of Minnesota. An earlier UMN document, “Summercrisp Pear” mentions that its original introduction to the UMN Horticulture Research Center was in 1933 by John Gaspard of Caledonia, Minnesota, and the parentage for Summercrisp is still mostly unknown to this day. Summercrisp trees are reliably hardy up to USDA hardiness zone 4. They can reach as tall as 15-20 feet with canopies that can grow as large as 20 feet wide, site and rootstock dependent. Summercrisp also is known for having decent resistance to fire blight as compared to many European pears.
Summercrisp pears are an earlier-season pear best harvested when the fruit is slightly under ripe with a crisp texture and a modest amount of color, which often coincides with mid-August timing in southern Minnesota.
Recommendations for optimal post-harvest handling for Summercrisp pears include refrigeration shortly after harvesting to uphold its texture and prevent it from ripening off the tree. Culinary uses for Summercrisp include preparation by grilling or searing slices, and/or adding it as an addition to a summer salad, using it for baked goods, or simply enjoyed as it is in its original fresh state.
Black currants are a fruit crop that are slowly emerging back into commercial production. Many varieties have some resistance to white pine blister rust, which is an invasive disease brought to the U.S. from Europe that previously led to the eradication of currants and prohibition of production in America.
The Savanna Institute is one organization leading the way with research related to black currants as they acquired the rights to propagate black currant varieties in 2022 bred by Richard McGinnis. The cultivars that are expected to be released first are named Savanna Zing and Savanna Zap and are for sale at a number of online nurseries.
I had an opportunity to sample both varieties at an event earlier this year that had been preserved by freezing. One of the varieties had flavors that reminded me of orange peel essence. Both were unique from other black currants I had previously tasted and also had fairly large berries. Most nurseries list these varieties as available by joining a waitlist. Savanna Zing is described as having an upright growth habit with fruits that have pleasant grape notes, with moderate rust resistance, and hardy from USDA zone 3-8. Savanna Zap has a spreading growth habit, has greater rust resistance, and resistance to powdery mildew. Both varieties are self-fertile.
To learn more information about black currant production, you can visit the Savanna Institute website where they have a pdf available for download.
Web page with pdf: Black Currant (Savanna Institute)
Last week was National Pollinator Week in the U.S.. With so many mid-season pollinator supporting plants currently in bloom, it’s a good time to celebrate the role pollinators play in our ecology and the diverse fruit crops grown in Minnesota.
Many fruit crops either require or benefit from insect-facilitated pollination. Supporting pollinators combines practices that encourage their populations on site and protects them from pesticides and habitat destruction.
The planning process to create pollinator habitat is most successful when it’s centered around crop-specific pollination goals, utilizing plants that attract specific pollinators and being aware of other site-specific factors like soil type and USDA growing zone to direct plant selection and site preparation choices.
To learn more about pollinator-friendly habitat installations, check out this week’s UMN Fruit and Veg News article.
Article: Planning for a pollinator-friendly habitat installation
To read the full article and learn more about Japanese beetles, check out the article link below:
Article: Japanese Beetle: First sighting of the year and the winsome fly parasitoid
Optimal timing for basal leaf and lateral shoot removal
Basal leaf removal, or removing leaves to expose developing grape clusters to sunlight, is one of the simplest and quickest ways to improve fruit quality in climates where the growing season is short. This week’s article goes into the research and best practices for post-bloom leaf removal, and highlights more recent research done in Michigan on the practice of pre-bloom leaf removal, which can promote looser clusters as a result.
To learn more, check out the following article.
Article: Optimal timing for basal leaf and lateral shoot removal
Pears
Variety highlight: Summercrisp
Images: Summercrisp pear coloration can vary based on whether fruits develop exposed to the sun (bottom), or are in the shade (top).
Summercrisp is one of four cold-hardy pear varieties released in 1986 from the University of Minnesota. An earlier UMN document, “Summercrisp Pear” mentions that its original introduction to the UMN Horticulture Research Center was in 1933 by John Gaspard of Caledonia, Minnesota, and the parentage for Summercrisp is still mostly unknown to this day. Summercrisp trees are reliably hardy up to USDA hardiness zone 4. They can reach as tall as 15-20 feet with canopies that can grow as large as 20 feet wide, site and rootstock dependent. Summercrisp also is known for having decent resistance to fire blight as compared to many European pears.
Summercrisp pears are an earlier-season pear best harvested when the fruit is slightly under ripe with a crisp texture and a modest amount of color, which often coincides with mid-August timing in southern Minnesota.
Recommendations for optimal post-harvest handling for Summercrisp pears include refrigeration shortly after harvesting to uphold its texture and prevent it from ripening off the tree. Culinary uses for Summercrisp include preparation by grilling or searing slices, and/or adding it as an addition to a summer salad, using it for baked goods, or simply enjoyed as it is in its original fresh state.
Black currant
Growth stage: Harvest
Image: The black currant variety Crusader is ready for harvest at Blue Fruit Farm, located near Winona, Minnesota.
Black currants are a fruit crop that are slowly emerging back into commercial production. Many varieties have some resistance to white pine blister rust, which is an invasive disease brought to the U.S. from Europe that previously led to the eradication of currants and prohibition of production in America.
The Savanna Institute is one organization leading the way with research related to black currants as they acquired the rights to propagate black currant varieties in 2022 bred by Richard McGinnis. The cultivars that are expected to be released first are named Savanna Zing and Savanna Zap and are for sale at a number of online nurseries.
I had an opportunity to sample both varieties at an event earlier this year that had been preserved by freezing. One of the varieties had flavors that reminded me of orange peel essence. Both were unique from other black currants I had previously tasted and also had fairly large berries. Most nurseries list these varieties as available by joining a waitlist. Savanna Zing is described as having an upright growth habit with fruits that have pleasant grape notes, with moderate rust resistance, and hardy from USDA zone 3-8. Savanna Zap has a spreading growth habit, has greater rust resistance, and resistance to powdery mildew. Both varieties are self-fertile.
To learn more information about black currant production, you can visit the Savanna Institute website where they have a pdf available for download.
Web page with pdf: Black Currant (Savanna Institute)
General fruit
About: Pollinator installations and support
Images: Pollinator resources often recommend planting three species of pollinator friendly plants, specific to your crop and region, for each bloom period (early, mid-season, late).
Last week was National Pollinator Week in the U.S.. With so many mid-season pollinator supporting plants currently in bloom, it’s a good time to celebrate the role pollinators play in our ecology and the diverse fruit crops grown in Minnesota.
Many fruit crops either require or benefit from insect-facilitated pollination. Supporting pollinators combines practices that encourage their populations on site and protects them from pesticides and habitat destruction.
The planning process to create pollinator habitat is most successful when it’s centered around crop-specific pollination goals, utilizing plants that attract specific pollinators and being aware of other site-specific factors like soil type and USDA growing zone to direct plant selection and site preparation choices.
To learn more about pollinator-friendly habitat installations, check out this week’s UMN Fruit and Veg News article.
Article: Planning for a pollinator-friendly habitat installation
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