Weekly Fruit Update - Sept. 7, 2022

UNIVERSITY OF MINNESOTA EXTENSION - www.extension.umn.edu

This is peak season for harvesting fruit crops in Minnesota. Thanks for taking a moment to read this fruit update, which will hopefully help with the harvest.

Apples

Orchards are harvesting Zestar!, SweeTango, Paula Red, and Chestnut Crabapples. The new Juicy Jewel pear was also recently picked at the Horticultural Research Center.  

Review recommendations on deciding when to pick, here.

Splitting: Some orchards experienced fruit splitting after the series of rainfalls two weeks ago. Un-irrigated orchards have more troubles with this than irrigated orchards. This is because apples that are water-stressed or slower-growing are less prepared for a large influx of water that occurs during heavy rainfall. The same principle applies with potato hollow heart - potatoes exposed to prolonged dry weather are more susceptible to internal cracking if they experience a sudden, heavy rainfall.

Harvesting the apple hail netting project into field crates on August 30 and Sept. 1, 2022.

Last week, we harvested our apple hail netting project. The project used SweeTango trees, and tested how well hail netting can exclude key insect pests while maintaining marketability and yield. The data will be analyzed over the winter, but initial observations showed that the apples in the net had similar yields and marketability, while having none of the bird damage of the un-netting apples.

Grapes

Some vineyards are harvesting Itasca this week. The UMN Grape Breeding and Enology program recommends targeting a pH of 3.0-3.3 and brix of 24-28 for Itasca. 

Edelweiss and Brianna also been harvested in the last week. The brix target is lower, between 14-17, with a pH at or below 3.3. 

Phomopsis on Marquette. Photo submitted by grower.

Watch for rot diseases on the clusters. Use the symptoms to determine what the problem is before attempting to treat it. Know the pre-harvest interval, cause, and the cost & benefit of spraying, before spraying anything. Growers are welcome to send me photos to help with diagnosis (kloddann@umn.edu).

• Botrytis: The berries have gray fuzzy fungal growth and are turning soft. The pedicels and rachises (cluster stems) are green.
• Sour rot: The berries are rotting but do not have fuzzy growth. They may have holes, appear wet, and have a vinegar smell. Associated with bird feeding damage and fruit flies. The pedicels and rachises are green.
• Phomopsis (see photo above): The berries are soft and desiccating. The pedicels and rachises have black/brown lesions and are desiccating as well. The canes probably have lesions, too.
• Bunch stem necrosis: Some of the berries are soft and desiccating. They declined suddenly. The rachises and pedicels associated with the soft berries are dried up all the way around (as opposed to having brown spots and lesions). There are no disease lesions on the rachises or canes.

Strawberries 

Strawberry plants growing back after renovation in White Bear Lake, MN. Photo: Annie Klodd

If you have some time now, start considering a fall weed management plan. Late summer/early fall is a good time to pull thistles and quackgrass because they are relatively energy-depleted compared to the spring. If you have stubborn weeds like nutsedge in your strawberries and use herbicides, fall is one of the only times you can spray effective products for nutsedge. Please refer to the Strawberries chapter of the Midwest Fruit Pest Management Guide to see which products can be sprayed in the fall for strawberry weeds.

This is still peak season for day-neutral strawberries. 

Look for insect, slug, and disease damage. Fruit with minor damage can still be used for processing into value-added products by removing the damaged parts. 

Day neutral strawberries grown in the open field without low tunnels or high tunnels are likely to exhibit fruit rots unless controlled with fungicides. Rot diseases include anthracnose and botrytis. Anthracnose makes brown depressions on the fruit, and botrytis usually displays fuzzy gray fungal growth. 

To control these effectively, consider both product choice and timing. 

Product choice: The products that are highly effective on one disease are not necessarily as effective on the other. If both diseases are present, or if you don't know which disease you have, use a fungicide such as Luna Sensation that is effective on both. The Midwest Fruit Pest Management Guide compares the options - please refer to this guide.

Timing: Even the most effective fungicides can be ineffective if applied at the wrong time. Apply protectant fungicides like Captan or Captivate before a rain, and kickback fungicides like Luna Sensation in the day after a rain. The longer the wait, the less effective they typically are. 

Many of the more experimental biofungicides recommend applying them prior to a rainfall as a protectant.  Make note of pre-harvest intervals; while many products have very short PHIs, they can still create a challenge when harvesting every day.

Other fruits

Aronia berries were harvested this week at Wright Farms in Hutchinson. With 10 acres of aronia, they needed to mechanically harvest. See the video of their mechanical harvester on their Facebook page.

Aronia berries hang heavy and ripe on a small branch at Wright Farms in Hutchinson, MN. Photo: Annie Klodd

For questions on other crops not listed here, please contact me at kloddann@umn.edu or your local horticulture Extension Educator.