Weekly fruit update July 28, 2021

Veraison on Marquette grapes. Photo: Annie Klodd

 

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

In this week's fruit update:

• Upcoming webinars
• Grapes
• Raspberries
• Blueberries
• Strawberries
• Honeyberries

Upcoming webinars:

• August 4 @ 1:00pm: What to Do Now in the Vineyard: Preparing for Harvest Season. Register here.
  
• August 5 @ 1:00pm:  Alternative Berry and Bush Crops to Boost Your Bank Account. Register here.
  

 

Apples

Attend next week's Minnesota Apple Growers Association Summer Tour. Friday, August 6th at 9:00am at Pine Tree Apple Orchard in White Bear Lake. Registration includes lunch. Register here.

Grapes

Veraison came incredibly early this year. We have a webinar next Wednesday, Aug. 4 to talk about preparing for harvest (see link above). It will also include an update on what the UMN Grape Breeding Program does during harvest.

An abbreviated list of veraison considerations:

• Finish any remaining foliar nutrient sampling, as it should be done at veraison and not long after
  
• Check pre-harvest intervals on fungicides, since harvest is approaching
• Bird pressure tends to be worst in dry years, because birds have less to eat in their natural habitat. If you typically put up bird netting in mid-August because it is ~2 weeks after veraison, it is time to put it up soon.
• Review last year's webinar on grape bunch rot diseases - make sure you can distinguish between fruit rots and know how to manage them
• Dig out your fruit sampling supplies (pH meter, pH buffers, refractometer, etc.) and make sure they still work
  

Raspberries 

I am not aware of anyone still picking summer-bearing raspberries at this time. Some fall-bearing raspberries are beginning to ripen, particularly in high tunnels and early varieties. 

What to keep an eye out for amid heat stress:

• Lower than average fruit set due to interrupted pollination
  
• Sunburn appears as white, hard spots on the side of the fruit that is directly exposed to sunlight.  
• Heat stress can also cause small, crumbly, or misshapen fruit
• Some varieties will also produce some double berries due to heat stress. Source.
  

Blueberries

Blueberry U-pick season is starting to wind down on farms around the Twin Cities. Little Hill Berry Farm in Northfield posted on their Facebook page that their last day for U-pick is today, July 28. Even after peak season, blueberry growers can choose either to reduce operations to pre-picked orders only, or handle U-pick business on a reservation-only basis to help ensure enough berries for each customer.

Strawberries

June-bearing strawberries may look like they are resting right now, but as long as they are being watered and weeded, they are actively growing leaves and next year's fruiting buds. Be sure to keep up on maintenance to support a big 2022 crop.

Day neutral strawberries are mid-season and will continue producing fruit through the fall. The relentless hot temperatures are causing lower than average yields as a result of reduced flower production and fruit development in temperatures above 85 degrees F. 

If yields are low right now, some patches may exhibit larger flushes of fruit later in the season once temperatures cool down. 

Much like myself, the optimal temperature range for day neutral strawberries is 45-85 degrees F.

Honeyberries

A honeyberry grower in northern Minnesota asked "Since harvest is over, is this a good time to apply foliar fertilizers for honeyberries?" 

Since minimal production recommendations exist for honeyberries, it took me a while to find an answer to this. I needed to know: 

1) Are foliar fertilizers recommended for honeyberries? Foliar sprays are not always helpful for fruit crops. And,

2) If a honeyberry grower wishes to apply them, is post-harvest a safe time to do that? 

I came across a small PDF guide from Dr. Bob Bors at University of Saskatchewan - one of the crops he specializes in is honeyberry. The guide recommends against applying any fertilizers to honeyberries after the springtime. Spring is the best time to fertilize, and fertilizer rates should be based on foliar and soil tests. Bors says that applying fertilizers in the summer or fall can result in late new growth, which impedes the plants' ability to harden off for the winter.

The guide is not dated, but I am unaware of any more updated recommendations since it was released.

A challenge for fertilizer application to honeyberries is that there are no well-established optimal nutrient values for this crop. Those recommendations are developed from research, and Bors' group seems to have been working on this but no formal optimal ranges were made.