Grand Rapids area tree fruit update – April 26, 2022

After a very warm weekend, expect a return to cold temperatures this week.

Gala, Honeycrisp and Fuji apple buds.
Gala, Honeycrisp and Fuji buds in Sparta, Michigan, on April 25, 2022. Photo by Anna Wallis, MSU Extension.

Weather and phenology update

What a difference a day or two can make! In the Grand Rapids, Michigan area, temperatures over the weekend were very warm, with highs in the upper 70s and low 80s and bud development was rapid. Usually, we can expect about three to five days between phenological stages. This weekend, we advanced one stage each day: green tip on Friday, 0.25-inch green on Saturday and 0.5-inch on Sunday.

As of April 25, the Michigan State University Sparta Enviroweather station has accumulated 195.9 growing degree days base 42 degrees Fahrenheit (GDD42). Despite the warm weekend, this is still below average, which is 221.8 GDD42. Significant rainfall was recorded across the region and fields continue to be wet. In most locations, approximately 1.5 inches were recorded on Thursday and Friday, and an additional about 0.2-0.4 inches were recorded on Sunday.

For the remainder of the week, expect a return to colder temperatures. Highs will be in the 40s and 50s, and little heat accumulation (GDD42) is expected. Low overnight temperatures on Tuesday and Wednesday evenings are expected to be in the upper 20s. Rainfall accumulation is expected to be minimal this week, with scattered showers possible on Thursday. Precipitation is expected again on Saturday evening into Sunday morning, with accumulation of approximately 0.25-0.5 inches.

Cold temperature concerns

As buds develop, they become more sensitive to cold temperatures and more susceptible to frost injury. You can find a table of critical spring temperatures for tree fruits from Michigan State University Extension. Keep in mind the temperatures reference for apples are averages based on Red Delicious, which is more sensitive to cold than many other varieties. Actual thresholds will be dependent on variety, specific trees and location.

Currently the low temperatures forecasted for Tuesday and Wednesday evenings are not predicted to reach the critical threshold for bud stages in most locations. Actual temperatures are likely to vary from the forecast and by specific location. For 0.5-inch green phenological stage, critical temperature thresholds for Red Delicious are 23 F for 10% and 19 F for 90% mortality. For tight cluster, the critical temperatures are 27 F for 10% mortality and 21 F for 90% mortality.

GDD table

Weather and GDD accumulation for Sparta, Michigan


Minimum temperatures

Maximum temperatures

Relative humidity

Rainfall (inches)

GDD42F (BE) since Jan. 1

GDD50F (BE) since Jan. 1

Sun, 05/01/2022 

46.0 F

58.8 F

72.8 %



Sat, 04/30/2022 

39.0 F

60.1 F

57.5 %



Fri, 04/29/2022 

36.1 F

56.8 F

59.9 %



Thu, 04/28/2022 

29.1 F

52.2 F

58.9 %



Wed, 04/27/2022 

27.0 F

46.0 F

61.7 %

0.02 in.



Tue, 04/26/2022 

34.9 F

40.1 F

69.3 %

0.10 in.



Mon, 04/25/2022 

46.9 F

55.5 F

74.0 %

0.03 in.



Sun, 04/24/2022 

55.3 F

71.9 F

75.0 %

0.33 in.



Sat, 04/23/2022 

44.7 F

81.6 F

70.2 %

0.00 in.



Fri, 04/22/2022 

38.0 F

50.2 F

78.5 %

1.43 in.



For these updates, we used averages for 1997-2021 from the Michigan Automated Weather Network (MAWN) to represent normal conditions. Weather data was gathered from MSU Enviroweather.

More information and reports on normal weather conditions and departures from normal can be found on the NOAA Climate Prediction Center website, NOAA U.S. Climate Normals website, NOAA Climate Normals Quick Access Page (which may be searched by region) and Midwest Regional Climate Center website.

Pest updates

Apple diseases

The primary apple scab game is underway and most weather stations in the general Grand Rapids area have had three or four wetting events, but most have not resulted in enough hours for infections. A few stations did have the first infection with the rain on Sunday, April 24. Primary apple scab spore numbers have been very, very low and we are not even to the 5% mature spore mark yet. From here on out until the end of primary spore release, maintaining adequate fungicide covers will be important.

Powdery mildew optimal conditions are warm and high humidity – it’s certainly too cold this week for mildew to be of concern.

Some insects to be thinking about now as you plan for monitoring and management.

Black stem borer – A few adults were active with the warm weekend weather. They will not be a worry until warm weather moves back in – temperatures above 60 F are needed.

Green fruitworm – This is a minor pest in tree fruit, but we still see some damage from larval feeding in any given year. Adult flight has been ongoing for about ten days in very low numbers.

Redbanded leafroller – Initial adult flight began late last week. Continue to monitor this minor tree fruit pest.

Spotted tentiform leafminer – The first adults began flying with the warm weekend weather. This insect hasn’t been a pest in many years, but if you’ve had high numbers, it’s best to trap for it to identify peak flight.

Obliquebanded leafroller - First overwintering larvae found in known hot spot. Colder weather will slow them considerably.

Aphids – A few apple grain aphids were found in non-managed apple terminals. Rosy apple aphids usually appear around pink.

San Jose scale - Overwintering scale are present. Management sprays should be considered for orchards where scale was present on fruit in the 2021 harvest and dormant oil is first management choice to consider.

European red mite – They are in the egg stage and not active in such cool temperatures. Monitor for overwinter egg mortality. If eggs look pale or clear instead of bright red, they are not viable.

Climbing cutworm – They will hang out in the soil until warmer weather and green tissue occur. While this is a very minor pest, we do see increased damage in a cool, drawn out spring as this year is.

Pear psylla - Adults could be present with the warmer weather of late. Expect increased adult activity near first green in pears and start management in high pressure blocks.

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