Southwest Michigan apple maturity report – August 21, 2024

Bill Shane<shane@msu.edu>, Michigan State University Extension - August 21, 2024

The mild winter and warm spring has pushed apple maturity earlier this year with apples up to 2 weeks ahead of normal, depending on the variety and location.

Pressure testing apples — Apple flesh firmness is tested by determining the pressure needed to sink a metal probe a set distance into a peeled apple. Photo by Bill Shane, MSU Extension.

This is our weekly southwest region apple maturity report. Reports are sent out following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning. View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.

2024 Overview

Crop loads in southwest Michigan are generally good, with some light crops due to poor pollination conditions during bloom. In general, apples in central southwest Michigan are predicted to mature as much as two weeks ahead of normal due to warm temperatures before and in the month after bloom. Crop maturity monitoring will be especially important this year to avoid storage problems. The Michigan apple crop forecast for 2024 is above average, as given at the USApple Outlook meeting on Aug. 16.

Gala (Standard)

Early season Gala strains such as Wildfire and Foxtrot are already mature and generally have already been harvested. The table gives a summary for main season gala varieties sampled from 5 orchards in Berrien County. Gala shows a range of maturities, testing immature to mature according to the starch and firmness tests, depending on the site. The predicted harvest date for 2024 for central Berrien County is Aug. 24, which is approximately two weeks ahead of the normal date of Sep. 8 for the region.

Collection Date	Red Color (%)	Firmness (lbs)	Starch (1-8)	Soluble Solids (°Brix)
Aug. 19	86 (70-98)	18.9 (16-22)	5.0 (2.8-7.4)	11.6 (11-12.3)

*Starch values according to the 1-8 scale developed by Cornell University.

Mac

Strains tested include Ruby and Linda Mac. Starch indices are in the immature range, below the mature threshold of 5. However, fruit firmness is relatively low, averaging 15.3 lbs, in the mid-range storage category. This is not ideal, indicating a potential for shorter shelf life for this variety in 2024. Predicted harvest date for central Berrien County in 2024 is August 25.

Collection Date	Red Color (%)	Firmness (lbs)	Starch (1-8)	Soluble Solids (°Brix)
Aug. 19	60 (20-98)	15.3 (14.4-16)	4.1 (4-4.2)	11.8 (11.3-12.8)

Early Fuji

Strains tested include Auvil Early Fuji and Daybreak Fuji. Starch indices are relatively high, with one site over the mature threshold of 3. Fruit firmness is averaging 20.0, relatively firm. Harvest can be delayed waiting for higher sugar content and better skin coloration.

Collection Date	Red Color (%)	Firmness (lbs)	Starch (1-8)	Soluble Solids (°Brix)
Aug 19	46 (30-67)	20.0 (17.7-22.2)	3.8 (2.8-4.8)	11.8 (11.3-12.8)

Honeycrisp

This variety is averaging 1.9 for the starch test--the mature starch threshold is 3.5. The current average firmness reading is 15.7 pounds, compared to the long-term CA target value of 16 pounds. The predicted peak harvest date for Central Berrien County is August 29. This variety should be watched closely—the relatively soft fruit and low starch test is not ideal. Use this link to see an article by MSU researcher Randy Beaudry for Honeycrisp harvest and storage recommendations.

Collection Date	Red Color (%)	Firmness (lbs)	Starch (1-8)	Soluble Solids (Brix)
Aug. 19	48.0 (45-55)	15.7 (14.3-16.4)	1.9 (1.4-2.8)	10.8 (10.3-11.4)

*Starch values according to the 1-8 scale developed by Cornell University.

Apple maturity sampling parameters

Color % = the visual percentage of red color (blush) from 0 to 100; range shown is for the orchard averages.
Firmness in lbs pressure, skin off, as measured with a FT Penetrometer; range is for the site averages.
Starch: 1 = all starch (solid blue staining), 8 = no starch (white); range is for the site averages. Starch Iodine Index Chart.
Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

Suggested firmness and starch index levels for long-term and shorter-term controlled atmosphere (CA) storage by variety
Variety	Firmness (lbs)*			Starch Index*
Variety	Short CA	Mid-CA	Long CA	Mature	Over mature
McIntosh	14	15	16	5	7
Gala	16	17	18	3	6
Honeycrisp	15	16	17	3.5	7
Empire	14	15	16	3.5	6
Early Fuji	16	17	18	3	7
Jonagold	15	16	17	3.5	5.5
Jonathan	14	15	16	3.5	5.5
Golden Delicious	15	16	17	3	6.5
Red Delicious	16	17	18	2.5	6
Idared	14	15	16	3.5	6
Fuji	16	17	18	3	7
Rome	15	16	18	3	5.5
Braeburn	16	17	18	2.5	7

See the following helpful resources for more information:

Predicted apple harvest dates for 2024 from MSU Extension.
More information on harvest management tools and timings from MSU Extension.
Post harvest treatments to extend apple life.
Guidelines from MSU Extension to check for apple maturity in your own orchard, including specific pressure and starch recommendations by variety.
Predicting apple maturity and starch chart from Cornell University.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).