Southwest Michigan apple maturity report – Oct. 7, 2020

Apple harvest is progressing rapidly in southwest Michigan due to sunny and dry conditions and light crops.

Red Delicious fruit in cross section
Red Delicious fruit in cross section showing watercore symptoms in the core and vascular bundle areas at the outer edge of the core. Note the holes at the outer edge of the apples are due from pressure testing. Photo by Bill Shane, MSU Extension.

General apple harvest comments

Golden Delicious is nearly all harvested in the area with growers working on Red Delicious, Romes and Ida Reds. Brown marmorated stink bug activity slowed over the past week due to cooler conditions. Adults are starting to move into buildings. San Jose scale can be seen here and there on fruit from older orchards where rough bark and abundant crevices make control of this insect more difficult.

Watercore symptoms are becoming more common in flesh of Red Delicious and Fuji, and some in Braeburn. Bright, sunny weather tends to increase watercore tendency. Watercore often reduces or disappears in storage but also is correlated with poorer shelf life. While watercore dissipates partially or even completely with storage, it tends to weaken fruit and cause future problems, including CO2 injury in storage. Orchards and varieties starting to show watercore should be higher priorities for harvesting, assuming they are sufficiently mature.

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 Oct. 5, 2020

Variety

Firmness lbs. (range)

Starch (range)

Brix %

Golden Delicious

15.9 (15.0–18.1)

5.8 (4.6–6.6)

14.9

Red Delicious

16.6 (16.2–17.0)

4.7 (4.2–5.6)

14.6

IdaRed

16.9 (15.4–18.4)

3.9 (2.8–6.8)

13.3

Fuji

18.2 (16.0–21.0)

4.3 (4.0–4.6)

14.0

Braeburn

23.7 (23.0–25.0)

2.4 (2.0–3.0)

11.9

Evercrisp

26.2 (25.4–27.0)

2.6 (2.2–3.0)

17.2

Rome

21.3 (20.0–22.1)

3.5 (3.0–4.6)

13.0

Individual variety results

Golden Delicious was sampled for the fourth week. Starch conversion this week is averaging 5.8, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 15.9 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 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

Sept. 28

16.8 (15.1-18.2)

4.5 (3.0-6.0)

14.1

Oct. 5

15.9 (15.0 – 18.1)

5.8 (4.6 – 6.6)

14.9

Red Delicious was sampled for the fourth week. Starch conversion this week is averaging 4.7, with 2.5 as the target for mature for this variety. Fruit firmness this week averaged 16.6 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. At least some watercore was seen in most fruit sampled in two orchards sampled.

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

Sept. 28

18.0 (17.1-19.0)

4.0 (3.2-4.6)

13.4

Oct. 5

16.6 (16.2 – 17.0)

4.7 (4.2–5.6)

14.6

Ida Red was sampled for the third week. Starch conversion averaged 3.9, with 3.5 as the target for mature for this variety. Fruit firmness this week averaged 16.9 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.

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

Sept. 28

18.4 (16.4-20.0)

2.5 (2.0-3.0)

11.9

Oct. 5

16.9 (15.4 – 18.4)

3.9 (2.8–6.8)

13.3

Fuji was sampled for the second week. Starch conversion averaged 4.3, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 18.2 pounds, with the general guideline of 17 pounds minimum firmness for best long-term CA storage. The internal starch readings indicates this variety is mature enough in some orchards to harvest. Newer strains of Fuji such as Aztec, Brak and Supreme with more red skin color are attractive enough to harvest. Harvest of older strains, particularly in cloudy autumns, is often delayed to wait for more red skin color development. Watercore symptoms are becoming easier to find in this variety.

Fuji maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 28

19.1 (19.0-19.2)

3.1 (2.4-3.8)

13.5

Oct. 5

18.2 (16.0 – 21.0)

4.3 (4.0–4.6)

14.0

Braeburn was sampled for the second 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. Watercore is starting to show up in some fruit.

Braeburn maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 28

24.0 (23.1-25.0)

2.4 (1.8-3.0)

11.6

Oct. 5

23.7 (23.0–25.0)

2.4 (2.0–3.0)

11.9

Evercrisp was sampled for the second time. Starch conversion averaged 2.6, with 3.0 as the target for mature for this variety. Fruit firmness this week averaged a very firm 26.1 pounds, the same as last week 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 lbs. (range)

Starch (range)

Brix %

Sept. 28

26.1 (25.2-27.0)

2.4 (1.8-3.0)

16.5

Oct. 5

26.2 (25.4 – 27.0)

2.6 (2.2–3.0)

17.2

Rome was sampled for the first time. Starch conversion averaged 3.5. All four sites tested averaged above 3.0 with 3.0 as the target for mature for this variety. Fruit firmness this week averaged 21.3 pounds, with the general guideline of 18 pounds minimum firmness for best long-term CA storage. Predicted peak harvest date for southwest Michigan is Oct. 7.

Rome maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Oct. 5

21.3 (20.0–22.1)

3.5 (3.0–4.6)

13.0

 

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* see Fuji section in report

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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