Weekly Fruit Update - May 11, 2022

SweeTango at tight cluster in Hastings, MN on May 9, 2022

 

Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production. kloddann@umn.edu

Welcome to the first weekly fruit update of the year! 

Apples

Apple trees around the Twin Cities are primarily at tight cluster this week. They are progressing quickly due to the warm weather.

Diseases: Potential apple scab infection event today, 5/11 in areas of the state impacted by tonight's predicted storms. This includes the Twin Cities metro. Check the NEWA website to check the chance of ascospore infection in your region. https://newa.cornell.edu/apple-scab

If you missed the opportunity to spray a protectant fungicide such as mancozeb for apple scab today, you may spray a fungicide with post-infection activity once the storms pass. Effective fungicide options are listed in the Apple Spray Program section of the Midwest Fruit Pest Management Guide (MFPMG).

Insects: If mites and/or aphids have been a problem, stylet oil or another horticultural oil like SunSpray or M-Pede (insecticidal soap) may be applied. They must actually contact the insects at application to be effective; they are not preventative and have no residual activity. This application should be skipped at this time if these insects have not been an economic problem in the past: Mite insecticides also harm beneficial mites, and there is little research quantifying the efficacy of these materials. Read more in the MFPMG v. 2021, page 52.

Other: We had a lovely pruning discussion at Carpenter Nature Center in Hastings last Monday. Thanks for the invitation, Sverre! 

 

Apple growers discuss pruning strategies on 5/9/22.

Grapes

Grapes are generally in bud swell around the metro - I have not seen reports from other areas of the state this week. Because of the slow bud progression so far, growers are advised to scout their vineyards for grape flea beetles from now until bud break. However, things will probably pick up quickly.

Diseases: If black rot, phomopsis, or anthracnose have been problematic in the recent past, lime sulfur may be applied during bud swell. This product must be applied before the buds show any green.

Insects: Grape flea beetle feed on grape buds as they swell. Bud swell is a critical time to scout for them, to prevent them from consuming important parts of the buds and reducing cluster formation. A small amount of feeding is ok, but severe feeding can cause noticeable yield reduction. Flea beetle damage tends to be worse in years with slow bud break, because the buds remain in a swollen state for longer.

Flea beetles only need to be sprayed in some years. There is no such thing as a preventative spray for flea beetles; do not spray unless populations are above the economic threshold. Read this article to decide if and when to spray.

Other: This is a good time to plant new grapevines. In my opinion, it is best to plant them before June 1 so that they have plenty of time to grow and harden off before winter. There may also be less watering required if they are planted during a rainy month.

Strawberries

Strawberries have been uncovered and are coming out of dormancy.

Diseases: Once blossom buds are visible, some growers may choose to do a fungicide application for powdery mildew, leaf diseases, and anthracnose if these diseases have been problematic in the past. However, the most critical period for disease control is a couple weeks away, after 5-10% bloom. 

Insects: Begin scouting for tarnished plant bug once the first blossoms start to open.

Other: 

• Hold off on nitrogen: Generally speaking, fertilizing mature strawberry fields with nitrogen before harvest is not advised, as excess N can increase vegetative growth at the expense of fruit production and quality. New strawberry fields not yet in fruit production can have N applied at this time or immediately before planting. 
• Watch the weather forecast for potential freeze and frost events as we enter this critical period.
  

Blueberries, honeyberries, etc.? For information on other fruit crops not listed, or for more information on these, please email Annie Klodd at kloddann@umn.edu.