Southwest Michigan apple maturity report – Sept. 30, 2020

Apple firmness and sweetness is excellent and U-pick operations have been especially busy this year.

Cut fruit being dipped in iodine solution
Cut fruit are dipped in iodine solution to test for internal maturity. As fruit mature, the interior stains less blue. Photo by Bill Shane, MSU Extension.

General apple harvest comments

Golden Delicious harvest is the main focus over the past week. Red Delicious is next in line. Harvest is progressing rapidly. Use of harvest management aids such as ReTain and Harvista have helped growers manage fruit drop and maintain good fruit firmness. Checking trees for signs of fruit dropping tendency is important to avoid loss. If fruit drop easily when a branch is struck with the hand, use stop drop.

Brown marmorated stink bug activity continues to increase with aggregation on buildings beginning the past week. Stink bugs are more active on sunny days. Perimeter sprays may be sufficient where this pest is detected. Statewide trap catch totals have been lower this year compared to the previous two seasons.

Codling moth catches over the past week have been near zero. Oriental fruit moth catch has declined to less than 10 per week.

Full rates of fungicides effective for flyspeck will protect fruit for about 21 days but less if removed by rain and is estimated to be removed completely by approximately 2 inches of precipitation. Infections established on apples can continue to develop during storage whenever temperatures are above 45 degrees Fahrenheit.

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. 28, 2020

Variety

Firmness pounds. (range)

Starch (range)

Brix %

Golden Delicious

16.8 (15.1-18.2)

4.5 (3.0-6.0)

14.1

Red Delicious

18.0 (17.1-19.0)

4.0 (3.2-4.6)

13.4

IdaRed

18.4 (16.4-20.0)

2.5 (2.0-3.0)

11.9

Fuji

19.1 (19.0-19.2)

3.1 (2.4-3.8)

13.5

Braeburn

24.0 (23.1-25.0)

2.4 (1.8-3.0)

11.6

Evercrisp

26.1 (25.2-27.0)

2.4 (1.8-3.0)

16.5

Cornell University starch test rating diagram.
Cornell University starch test rating diagram.

Individual variety results

Golden Delicious was sampled for the third week. Starch conversion this week is averaging 4.5, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 16.8 pounds, with the general guideline of a minimum of 17 pounds firmness for best long-term controlled atmosphere (CA) storage. The predicted peak harvest date is Sept. 27 for central Berrien County, which seems to be on target.

Golden Delicious maturity sampling for the harvest season

Sample date

Firmness pounds. (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

Sept. 28

16.8 (15.1-18.2)

4.5 (3.0-6.0)

14.1

Red Delicious was sampled for the third week. Starch conversion this week is averaging 4.0, with 2.5 as the target for mature for this variety. Fruit firmness this week averaged 18.0 pounds, with the general guideline of a minimum of 17 pounds firmness for best long-term CA storage. Based on these data, harvest for CA storage could begin in some sites. 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 pounds. (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

Sept. 28

18.0 (17.1-19.0)

4.0 (3.2-4.6)

13.4

IdaRed was sampled for the second week. Starch conversion averaged 2.4, with 3.5 as the target for mature for this variety. Fruit firmness this week averaged 18.4 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. Good firmness will allow delay of harvesting to wait for more starch conversion.

IdaRed maturity sampling for the harvest season

Sample date

Firmness pounds. (range)

Starch (range)

Brix %

Sept. 21

19.0 (18.0-21.0)

1.6 (1.0-2.2)

12.3

Sept. 28

18.4 (16.4-20.0)

2.5 (2.0-3.0)

11.9

Fuji was sampled for the first time. Starch conversion averaged 3.1, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 19.1 pounds, with the general guideline of 17 pounds minimum firmness for best long-term CA storage. The predicted peak harvest date is Oct. 22 for central Berrien County. The internal starch reading indicates that this variety may be ready before the predicted peak harvest date. This variety tends to soften slowly, taking away the urgency to harvest.

Fuji maturity sampling for the harvest season

Sample date

Firmness pounds. (range)

Starch (range)

Brix %

Sept. 28

19.1 (19.0-19.2)

3.1 (2.4-3.8)

13.5

Braeburn was sampled for the first time. Starch conversion averaged 2.4, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 24 pounds, with the general guideline of 18 pounds minimum firmness for best long-term CA storage. The predicted peak harvest date is Oct. 28 for central Berrien County. This variety has quite a way to go before it is mature.

Braeburn maturity sampling for the harvest season

Sample date

Firmness pounds. (range)

Starch (range)

Brix %

Sept. 28

24.0 (23.1-25.0)

2.4 (1.8-3.0)

11.6

Evercrisp was sampled for the first time. Starch conversion averaged 2.4, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged a very firm 26.1 pounds, with the general guideline of 18 pounds minimum firmness for best long-term CA storage. Firmness was probably higher than measured because some apples maxed out the penetrometer. Brix is already averaging 16.5, with one orchard averaging over 18. This variety is harvested late in October to early November.

Evercrisp maturity sampling for the harvest season

Sample date

Firmness pounds. (range)

Starch (range)

Brix %

Sept. 28

26.1 (25.2-27.0)

2.4 (1.8-3.0)

16.5

 

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. 22

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 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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