Southwest Michigan apple maturity report – Sept. 23, 2020

Gala harvest is winding down with Honeycrisp continuing and Golden Delicious and Red Delicious right around the corner. Weather conditions have been excellent for working in orchards.

Honeycrisp apples
Honeycrisp apples have excellent quality this year. Photo by Bill Shane, MSU Extension.

General apple harvest comments

Southwest Michigan growers are finishing up harvests of Gala and Honeycrisp. Growers are putting out bulk boxes in Red Delicious and Golden Delicious blocks as the next varieties to be harvested.

Brown marmorated stink bug trap catch numbers increased markedly over the past week. Aggregation of this insect on sunny sides of buildings has not started yet. Stink bugs are more active on sunny days like those in the last and coming week. Trap catches for codling moth are dwindling, oriental fruit moth catches are still significant and obliquebanded leafroller catch is nearly done in southwest region orchards.

Problems with flyspeck disease usually develop after late summer rains remove fungicide protection, followed by approximately 270 hours of leaf wetting prior to harvest. Full rates of fungicides effective for flyspeck will protect fruit for about 21 days but less if removed by rain—estimated to be removed completely by approximately 2 inches of precipitation. Storage of fruit above 45 degrees Fahrenheit will allow active infections to continue to develop.

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.

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.

Apple maturity in southwest Michigan for apples harvested Sept. 21, 2020

Variety

Firmness lbs. (range)

Starch (range)

Brix %

Gala

20.6 (19.0-22.0)

4.7 (3.2-5.6)

14.5

Empire

17.7 (17.3-18.4)

3.4 (2.0-4.2)

11.0

Jonagold

17.1 (`6.-19.0)

5.0 (4.0-6.4)

13.7

Golden Delicious

17.1 (14.4-18.2)

2.2 (1.0-4.0)

13.7

Red Delicious

18.1 (17.4-19.0)

2.9 (2.6-3.0)

11.9

Ida Red

19.0 (18.0-21.0)

1.6 (1.0-2.2)

12.3

Individual variety results

Gala harvest is nearly done in the area with relatively good firmness readings, similar to last week, and brix averaging 14.5. Starch readings for individual orchards were over 3 with the overall average of 4.7, all considered internally mature. This has been a good quality year for Gala. The predicted harvest date for southwest Michigan in 2020 is Sept. 11, which was pretty much on target.

Gala maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 31

20.6 (18.3-23.0)

4.3 (2.0-6.4)

11.5

Sept. 7

22.6 (22.0-23.0)

4.2 (3.6-5.0)

13.8

Sept. 14

21.1 (18.2-22.4)

4.1 (2.0-6.6)

13.4

Sept. 21

20.6 (19.0-22.0)

4.7 (3.2-5.6)

14.5

Empire was sampled for the third week. Firmness has dropped over 2 pounds over the past week to 17.7 pounds and the starch conversion index increased to 3.4, close to the target starch test 3.5 for mature apples destined for fresh market or fresh apple slices. The target is 16 pounds firmness or more for long-term controlled atmosphere (CA) storage. Predicted harvest dates for fresh market for central Berrien County is Sept. 21, which seems to be about on track.

Empire maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 7

20.4 (18.0-23.0)

2.0 (1.4-2.4)

11.7

Sept. 14

20.1 (19.0-24.0)

2.1 (1.6-3.0)

12.6

Sept. 21

17.7 (17.3-18.4)

3.4 (2.0-4.2)

11.0

Jonagold was sampled for the third week. Starch conversion this week is averaging 5.0 with 3.5 as the target for mature for this variety. Fruit firmness this week averaged 17.1 pounds with the general guideline of a minimum of 17 pounds firmness for best long-term CA storage. The predicted peak harvest date is Sept. 24 for central Berrien County.

Jonagold maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 7

19.4 (18.2-21.0)

2.0 (2.0-2.0)

12.0

Sept. 14

18.2 (16.4-21.0)

3.2 (2.0-4.6)

12.9

Sept. 21

17.1 (`6.-19.0)

5.0 (4.0-6.4)

13.7

Golden Delicious was sampled for the second week. Starch conversion this week is averaging 2.2 with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 17.1 pounds with the general guideline of a minimum of 17 pounds firmness for best long-term CA storage. The predicted peak harvest date is Sept. 27 for central Berrien County. Decrease of firmness is ahead of starch conversion development.

Golden Delicious maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 14

18.4 (17.0-20.0)

1.3 (1.0-1.8)

12.2

Sept. 21

17.1 (14.4-18.2)

2.2 (1.0-4.0)

13.7

Red Delicious was sampled for the second week. Starch conversion this week is averaging 2.9 with 2.5 as the target for mature for this variety. Fruit firmness this week averaged 19.0 pounds with the general guideline of a minimum of 17 pounds firmness for best long-term CA storage. This is a good situation when the fruit are internally mature while the fruit firmness is still relatively high. The predicted peak harvest date is Sept. 30 for central Berrien County—fruit maturity development looks to be slightly earlier than the predicted date.

Red Delicious maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 14

18.7 (18.1-19.0)

2.1 (1.8-2.4)

11.9

Sept. 21

18.1 (17.4-19.0)

2.9 (2.6-3.0)

11.9

Ida Red was sampled for the first time. Starch conversion averaged 1.6 with 3.5 as the target for mature for this variety. Fruit firmness this week averaged 19 pounds with the general guideline of 16 pounds minimum firmness for best long-term CA storage. The predicted peak harvest date is Oct. 7 for central Berrien County.

Ida Red maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 21

19.0 (18.0-21.0)

1.6 (1.0-2.2)

12.3

 

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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