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| Attendees of the MN Apple Grower's Association annual tour say a demonstration of hail netting being applied and removed at Pine Tree Apple Orchard, August 6, 2021. Photo: Annie Klodd. |
Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production. kloddann@umn.edu
In this week's fruit update:
- Japanese beetles
- Apples
- Grapes
- Day-neutral strawberries
- June-bearing strawberries
Help direct research and Extension priorities for Japanese beetles:
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| Japanese beetles feeding and mating on an apple leaf. Photo: Annie Klodd |
Apples
For the most part, recommendations in last week's fruit update also apply this week. When I did starch-iodine testing on First Kiss and SweeTango on Friday, neither variety was anywhere near ready to pick. However, First Kiss can ripen up quickly toward the end.
To-do list:
- Order iodine solution and do starch-iodine testing for ripeness. For early varieties (First Kiss and Zestar!) bi-weekly testing is best at this time. For SweeTango, test weekly, as this variety will likely ripen within the next 4 weeks. For later ripening varieties, you can wait to start testing for another couple of weeks.
- Apply a stop-drop spray on First Kiss if you haven't already. This should be done 2 weeks before anticipated harvest. First Kiss is usually harvested in the second 2 weeks of August.
- Continue scouting for apple maggot (AM) and codling moth (CM), both of which are still quite active. Pheromone traps are the best way to quantify CM and AM pressure. Spray if necessary. Monitoring and economic thresholds for codling moth are discussed in this article. The economic threshold for apple maggot is set at one fly per trap per week with unbaited traps or five flies per week on baited traps. Source.
- Evaluate tree health and disease while out in the field. Good record keeping helps in planning for next year. This photo below is of cedar apple rust infection on fruit. Note the lack of a characteristic orange rust, meaning that this infection may be relatively fresh.
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| Cedar apple rust infection on an apple, August 4, 2021 near Excelsior, MN. Photo: Annie Klodd. |
Grapes
As we know, veraison was about 2-3 weeks early in Minnesota this year, depending on variety. Yesterday, I spoke to two growers who said their Marquette brix were at 16 and 19, respectively.
Be sure that bird netting goes on this week if it hasn't already. Bird netting is still the most reliable method for managing birds, according to multiple studies. Several studies have also tested bird repellent sprays of methyl anthranilate and found it ineffective at repelling birds; therefore we do not recommend these products. See our publication Comparing Bird Management Tactics for Vineyards and Berry Crops where we discuss all of this in detail.
To do-list:
- Scout for powdery mildew. Captan is an effective preventative for PM. If a PM infection is already present and visible, use a systemic fungicide that will stop the spread of existing infections. Use the Midwest Fruit Pest Management Guide's Grape Spray Program for a list of effective products for PM.
- Apply bird netting
- Spray for Japanese beetles if needed
- Test brix and pH of berry samples at least weekly. Use the Growing Grapes in Minnesota guide to see brix, pH, and TA targets.
Day Neutral Strawberries
August has been shown as a peak harvest time for day neutral strawberries, in research conducted by University of Minnesota. Hopefully the temperatures will continue to stay below 85 degrees the next few weeks, allowing us to get lots of berries.
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| Tarnished plant bug damage to strawberries. Photo: University of Maine. |
Tarnished plant bug (TPB) - This insect pest remains throughout much of the day neutral strawberry growing season. It is responsible for "catface" deformation on fruit, rendering the fruit unmarketable for fresh-eating but still usable for processing.
Since day-neutrals are continually in bloom from June to October/November, growers should choose insecticides with low pollinator risk and spray in the very early morning or late at night when pollinators are less active. This goes for both organic and conventional insecticides.
- The organic insecticides with the best documented efficacy against TPB contain nullachtin (i.e. Azera, Ecozin Plus, others). Azadirachtin is relatively low risk for bee.
- The conventional products with the lowest pollinator risk, that are still effective on TPB, are Beleaf and Rimon. Again, it is still best to spray during non-peak times of day for bees in order to minimize risk.
- Scout regularly to know whether or not spraying is necessary; also, keep weeds down in and around the field to reduce TPB populations.
For full information, read this week's article Managing Tarnished Plant Bug on Day-Neutral Strawberries
For more information on managing day-neutral strawberries, see: Day-Neutral Strawberries
June-bearing Strawberries
Aside from weeding and watering, you may choose to do soil testing around this time. This will prepare you to amend the field appropriately this fall if needed. While fertilization is usually done at renovation, many nutrients like phosphorus (P) and potassium (K) can still be applied safely this fall.
Soil pH amendments (sulfur and lime) can also be incorporated if needed. While it's too late to cultivate safely in the rows, growers can cultivate between rows to incorporate sulfur or lime.
It is best to avoid applying nitrogen (N) at this time. Late-season N can cause the plants to put on excess growth at a time when they should instead be moving resources down to the roots for overwintering. The result is reduced winter survival.
Please visit our Strawberry Nutrient Management page for nutrient recommendations.
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