West central Michigan small fruit update – April 27, 2021

An update on freeze/frost effects on small fruit production including strawberries and blueberries in west central Michigan.

Bluecrop terminal flower clusters affected by freezing temperatures.
Bluecrop terminal flower clusters affected by freezing temperatures on April 12 and 22, 2021, in Covert, Michigan. Photo by Carlos Garcia-Salazar, MSU Extension.

During the past two weeks, west central Michigan experienced several days with temperatures below freezing. This sudden drop in daily minimum and maximum temperatures put plant growth on hold, and development was very slow in all small fruit crops including blueberries, strawberries and raspberries.

The early spring in west central Michigan advanced plant growth and development in strawberries, raspberries and blueberries by more than two weeks in the southern part of the state, and up to seven day in counties in west central Michigan. However, weather conditions changed starting April 17 when we observed a series of freeze/frost events whose effects had a slight impact on strawberries, raspberries and blueberries. Overnight temperatures dropped below freezing and remained in the mid 40-50s until April 21 and 22 when we experienced a new cold front that once again dropped nightly temperatures below freezing (Table 1).

Table 1. Overnight temperatures (degrees Fahrenheit) at selected MSU Enviroweather stations in west central Michigan at midnight April 20 to early morning April 21, 2021.

 Station

10-11 p.m.

11 p.m.-midnight

Midnight-1 a.m.

1-2 a.m.

2-3 a.m.

3-4 a.m.

4-5 a.m.

5-6 a.m.

6-7 a.m.

Allegan

31.1

29

27.5

26.6

26.1

26.1

25.9

27.4

28.1

Fennville

31.1

28.9

27.2

26.6

29.3

28.1

26.2

32.5

32.5

Grand Junction

28.5

26.2

26.6

26

26

26

27.1

28.3

27.5

South Haven

30.8

28.8

27.4

26.4

26.1

27.1

28.1

34.7

36.7

Hudsonville

29.6

27.8

26.4

25.7

25.2

23.9

23.6

24.2

27.7

West Olive

30.7

28.3

27

27

25.2

24.7

24.1

27

31

The weather information from Enviroweather indicated that freezing temperatures started at midnight on April 20 and continued for several hours until 7 a.m. on April 21. Only at Hudsonville did nightly temperatures drop to 23-24 F for a short period of time. The same condition occurred on April 22 with similar temperatures.

On April 22, 23 and 26, we conducted inspections of blueberry and strawberry fields from Covert, Michigan, to Belding, Michigan, and at fields around Fennville, Michigan, and West Olive, Michigan. We inspected the main blueberry varieties which were in the more advanced growth stages: Duke, Bluecrop and Elliott. At selected fields, we collected shoot samples and dissected the terminal flower buds to investigate the conditions of flowers cluster after the freeze/frost events.

Our evaluation found little damage in most varieties. At the time of the freeze/frost events, blueberries were at growth stages that can tolerate freezing temperatures above 24 F. Only in one Bluecrop blueberry field close to Lake Michigan in Covert did we find terminal flower buds that were in the early pink stage and sustained more damage than blueberries at fields around Grand Junction or at northern locations, i.e., Allegan, Ottawa and Ionia (see photo at beginning of article). It is too early to determine the effect of those freeze/frost events on blueberry production at those affected fields or across the industry. More will be known about the crop potential for 2021 after bloom in mid-June.

On the other hand, strawberries were in an early developmental stage and only slight damage was observed at fields that were inspected at Ionia and Ottawa County. It is necessary to continue this evaluation to have a better picture of the effect of those weather events on small fruit production in west central Michigan.

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