Southwest Michigan apple maturity report – Sept. 2, 2020

Gala maturity is advancing rapidly. Recent rains are helping fruit to size.

General apple harvest comments

The May 9, 2020, freeze took its toll on the southwest Michigan apple crop. Varieties that have generally fared better include Golden Delicious and Jonathan. Irrigation has been very helpful this year to help size fruit on sandy sites. Southwest Michigan growers have been harvesting early season Wildfire Gala and Premier Honeycrisp varieties, Gingergold and Zestar.

The predicted harvest dates are based on temperatures from spring to 30 days after bloom and do not take into account summer temperatures which can push development earlier or later than predicted. Hot weather over the past 30 days has stimulated internal ethylene levels in apple fruit and pushed along apple development.

Brown marmorated stink bug numbers are slowly increasing. Fruit are generally clean, however sooty blotch and flyspeck disease symptoms are common on unprotected fruit in abandoned orchards, indicating that fungicide protection has been needed.

Samples collected for this report are from the central Berrien County region, targeting more mature fruit on the outside of the tree canopy. Fruit in the interior of the tree will be less advanced than shown here. Sites with heavier soils and greater crop loads will generally be less mature.

Apple maturity in southwest Michigan for apples harvested Aug. 31, 2020

Variety

Firmness lbs. (range)

Starch (range)

Brix %

McIntosh

16.0 (16.0-16.0)

3.3 (3.0-3.6)

12.1

Gala

20.6 (18.3-23.0)

4.3 (2.0-6.4)

11.5

Honeycrisp

19.0 (18.9-19.0)

1.3 (1.0-1.8)

12.1

Individual variety results

Zestar at the Southwest Michigan Research and Extension Center is testing 14 pounds firmness, starch test of 5.8, and 14.8 brix.

Kinderkrisp is averaging 19 pounds firmness, starch test of 6, and 15.5 brix.

McIntosh starch readings for the area average 3.3, below 5, the internal mature threshold. Firmness is averaging 16 pounds, the firmness recommended for long-term controlled atmosphere (CA) storage. Hot conditions have slowed blush development. The predicted harvest date for southwest Michigan in 2020 is Sept. 13.

Gala starch readings indicate some orchards have fruit that are internally mature (3 or above), but with excellent firmness that will allow harvest to be delayed to wait for better fruit size and sugar (brix). Dry conditions in many southwest area orchards have slowed fruit sizing. Skin color is generally good to very good, with some of the newer red strains nearly solid red. The predicted harvest date for southwest Michigan in 2020 is Sept. 11. Hot weather is apparently pushing maturity a few days earlier than predicted.

Honeycrisp starch readings are averaging 1.3 with a target mature starch index of 3.5 for this variety. The current average firmness of 19.0 is above the general guideline of 17 pounds for best long-term CA storage. The predicted peak harvest date is Sept. 15 for central Berrien County. The fungal disease bitter rot favored by hot conditions and is being detected again this year on this variety.

Normal and predicted 2020 peak harvest dates for apple varieties in central Berrien County in southwest Michigan based on weather data at the Southwest Michigan Research and Extension Center in Benton Harbor, Michigan.

Variety

Normal date

2019 Predicted peak harvest date

2020 Predicted peak harvest date

Paula Red

Aug. 22

Aug. 28

Aug. 25

Zestar

Aug. 22

Aug. 28

Aug. 25

Gingergold

Aug. 20

Aug. 26

Aug. 23

McIntosh

Sept. 10

Sept. 16

Sept. 13

Gala

Sept. 8

Sept. 14

Sept. 11

Early Fuji

Sept. 3

Sept. 10

Sept. 6

Honeycrisp

Sept. 13

Sept. 20

Sept. 15

Empire

Sept. 19

Sept. 26

Sept. 21

Jonathan

Sept. 22

Sept. 30

Sept. 24

Jonagold

Sept. 22

Sept. 30

Sept. 24

Golden Delicious

Sept. 25

Oct. 1

Sept. 27

Red Delicious

Sept. 28

Oct. 7

Sept. 30

Ida Red

Oct. 5

Oct. 15

Oct. 7

Rome

Oct. 5

Oct. 15

Oct. 7

Fuji

Oct. 20

Oct. 28

Oct. 22

Braeburn

Oct. 20

Oct. 28

Oct. 2

Goldrush

Oct. 26

Nov. 3

Oct. 28

 

Suggested firmness and starch index levels for long-term and shorter-term controlled atmosphere (CA) storage by variety.

Variety

Firmness (pounds)*

Starch Index*

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

*Firmness is measured with a mechanical 11-millimeter wide probe inserted into the pared flesh of a fruit to a distance of 8 millimeters. Starch index is measured on equatorial cross section of an apple stained with iodine solution and rated using the Cornell University starch-iodine index chart for apples on a 1-8 scale (Predicting Harvest Date Window for Apples by Blanpied and Silsbey, Cornell Extension Bulletin 221.)

Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.

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