Author: Annie Klodd, UMN Extension Educator - Fruit and Vegetable Production
This week's update includes information on: judging apple ripeness, grape harvest parameters and lady beetle management, and day neutral strawberry disease control.
Apples
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| Using the starch iodine test on First Kiss apples shows the correlation between a calyx color and level of ripeness. Photo: Annie Klodd. |
First Kiss harvest is going on this week. To determine if your First Kiss apples are ready for harvest, check out this article.
Zestar! apples may be ready now or in the next week. They should ideally have a yellow background color, not a green background color, when ripe.
SweeTango apples were still too starchy to harvest in southeast Minnesota and the Twin Cities metro this week. If you are harvesting for long-term storage, a higher starch content is acceptable, but apples meant for direct sales to customers (i.e. eaten shortly after purchase) should be left on the trees for at least another week to sweeten and improve in mouthfeel.
The most precise way to judge ripeness is to use the starch-iodine test. It can be done in the field in a few minutes, with a knife and spray bottom of iodine. This involves spraying a starch solution on the cut surface of an apple and looking for a blue stain. The amount of blue stain is correlated to the amount of starch in the apple, with riper apples having less staining. Refer to this article for information on conducting this simple test.
Codling moth and apple maggot are still active; traps we monitor in Preston contained anywhere between 0-15 codling moths on Tuesday. If fungicide or insecticide sprays are still needed, make sure that the products have short pre-harvest intervals.
Grapes
As harvest approaches, we get questions about what brix and pH numbers to target. Last year, the grape team created 1-page recommendation sheets for each modern UMN grape variety that contain our recommended harvest parameters. Find them all here: https://enology.umn.edu/growing-grapes/cultivars
Netting should ideally be on at this point, or other control measures like bird speakers and cannons should be operating to protect fruit. Netting remains the most reliable bird control method.
Look out for Multi-colored Asian lady beetles before harvest. If present, they should be controlled prior to harvest so that they do not get crushed with the juice. This article provides more information: https://fruit.wisc.edu/2018/09/07/multicolored-asian-lady-beetle-a-harvest-time-grape-pest/
Strawberries
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| Day-neutral strawberries. Photo: Gigi DiGiacomo |
We are still in peak harvest season for day-neutral strawberries. This means a lot of picking every day!
I have received a few photos of rot spots on fruit. 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 both anthracnose and botrytis. Anthracnose makes brown depressions on the fruit, and botrytis usually includes 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 is extremely important as well: Even the most expensive 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.
This is why a standard spray schedule such as "every 10 days" may not be effective even though it is very diligent. A lot 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.
For questions on other crops not listed here, please contact me at kloddann@umn.edu or your local horticulture Extension Educator.
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