Final Weekly Fruit Update of 2021

 

Customers walk through rows of U-pick SweeTango apples at Pleasant Valley Orchard in Shafer last weekend. Photo: Annie Klodd.

Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production 

In this week's update: Grapes, apples, fall raspberries, and day neutral strawberries (Webinar alert!)

While apple, grape, and fall raspberry growers are busy harvesting, the amount of relevant weekly alerts slows down at this point as fruit comes off of the trees and vines. 

Therefore, this will be my last weekly fruit update of the season, but I will continue to provide recommendations on post-harvest tasks through stand-alone articles this fall. I will also continue to field questions that come in via email (kloddann@umn.edu), phone, and text message.

 

Grapes

We just released a set of grape growing recommendation sheets for each of the UMN varieties and Edelweiss. Please click here to access these fact sheets, which include canopy management, pruning, harvest parameters, and more.

Rainfall impacts on ripening: 

• I received questions in the last week about brix stalling or decreasing after recent rains. Increased water temporarily dilutes sugar content in the berries and often has the effect of delaying harvest. As long as the fruit is still healthy and is not being heavily infested with wasps or birds, it should be left to hang until ripe. 
• Speaking of wasps, rainfall can also increase the frequency of wasps in the vineyard as they are attracted to split fruit. OxiDate can be sprayed to help dry up grapes that have split due to heavy rainfall. As mentioned in previous articles, no insecticides are labeled for control of wasps, but spraying for Multicolored Asian Lady Beetles may also kill wasps, depending on what is sprayed. These sprays are expensive, so consider the economic cost and benefit of spraying. Refer to this article on wasps from August 18 or more information.
• If ripening is going slowly, some growers may be tempted to remove leaves or shoots to expose the clusters to more sun. This is not advisable as it has multiple negative impacts this late in the season, including grape sunburn and reducing winter hardiness. Any leaf removal or shoot thinning should have been safely completed in May through July.
  

Grape harvest will be all but over in a handful of weeks, with the exception of the occasional ice wine harvest. Harvest dates for each variety have been highly variable from vineyard to vineyard, which is completely fine and expected.

• Many vineyards are harvesting Marquette sometime this week or this weekend, while others finished Marquette harvest last week. Of course this is earlier than the average year, as Marquette harvest usually happens the last week in September. Look for a pH of 2.9-3.3 and brix of 22-26.
  
• Most LaCrescent has come off of the vines at this point.
  
• Frontenac harvest is yet to come, and growers should wait until the pH is above 3.0 before harvesting. Frontenac wines are higher in quality and have less "green" or vegetal qualities when the fruit is allowed to lose some of its natural acidity. At the same time, we also understand the challenge of letting fruit hang if birds or splitting have become severe.
  
• Frontenac blanc: Harvest between 2.9-3.2 pH and 22-26 brix
• Frontenac gris: A good harvest pH is typically above 3.0, and 23-26 brix

I will follow up in the coming weeks about post-harvest sprays for powdery mildew, fall herbicides, and fall fertilizing. 

Apples 

UMN enology specialist Drew Horton uses a cold press juicer to process apples for our cider apple variety evaluation research, 9/3/2021. Photo: Annie Klodd

Apple harvest is going strong. We are currently in the in-between period after the "early varieties" like SweeTango and Zestar! and right at the start of the group of mid- and late-season varieties that includes Chestnut crabapples and Honeycrisp. 

• Honeycrisp harvest starts this week in southern locations of the state and for the earlier Honeycrisp sports. If you are interested in using the starch-iodine test for Honeycrisp, use this chart, which is designed specially for Honeycrisp. 
• Honeycrisp should not be sold if the undercolor is still predominately green. This runs the risk of diluting the reputation of the variety, as the flavor and texture will be sub-optimal.
• Honeycrisp storage has been heavily researched due to the finicky nature of Honeycrisp in storage. This article gives valuable information but much of it might be overkill for the Minnesota growers who are only storing fruit for a short period before on-farm sales. Importantly, they do recommend conditioning for 7 days at 50 degrees F followed by a final storage temperature of 37-39 degrees F. It may be helpful to remind customers to store Honeycrisp in the refrigerator for better longevity, as not everyone knows the importance of cooling for apples.
  

Rainfall impacts: The rainfall did cause some cracking, which was certainly more severe in some orchards than others. A heavy rainfall after a period of dry weather tends to increase cracking as the fruit take on more water than they have the capacity for.

I will follow up later in the harvest season with recommendations about post-harvest tasks.

 

Fall-Bearing Raspberries and Day Neutral Strawberries

Please consider attending our Oct. 21 webinar on constructing a tabletop strawberry growing system, with UMN graduate researcher Kate Fessler. Register here.

These two berry crops will continue producing berries until the first killing frost. Those growing in high tunnels or low tunnels still have a few weeks of harvest ahead of them. 

For those considering growing fall raspberries or day neutral strawberries, a recent questionaire distributed by the Minnesota Farmers Market Association received responses indicating that the demand for berries at fall markets is high. 

We recently released a detailed guide on growing high tunnel raspberries. Click here to download it.

Cane dieback on summer-bearing raspberries that had been diagnosed with phytophthora root and crown rot. Photo: Annie Klodd.

Last week, a couple of us made a trip to southwestern MN to help a raspberry grower brainstorm solutions for a field that was diagnosed with phytophthora root rot. If you suspect disease issues in your berries, you are welcomed to submit samples to the Plant Disease Clinic. It usually increases diagnostic success if you contact me or another Extension Educator first about what tissue to submit.