Southwest Michigan apple maturity report – September 16, 2015

This is the third weekly report of the MSU apple maturity program for southwest Michigan.

General comments for this week

Most larger Gala blocks have been picked and many Honeycrisp blocks have been spot picked at least once. Growers should keep a close eye on Jonagold and Jonathan which are testing relatively mature, and are ahead of the predicted harvest dates. First test of Golden Delicious shows some starch conversion, but has a ways to go before they are mature for fresh market. Red Delicious appears that it may mature before the predicted harvest date. We speculate the recent hot weather may have spurred the maturity to be earlier than predicted.

Detailed tests for this week – see suggested firmness and starch levels for harvest in Table 1

Most Gala blocks intended for controlled atmosphere (CA) storage have already been picked. Some of the remaining apple blocks are starting to develop waxy/slight greasy feel to skin that signals well mature Gala. The predicted long-term storage harvest date for 2015 for the Southwest Michigan Research and Extension Center (SWMREC) is Sept. 7. Five of five sites tested this week above the target index of 3 for sufficient starch conversion for good quality for immediate sales. Firmness is still very good and is sufficient for long-term CA storage, but the recent jump in starch conversion indicates firmness will be dropping steadily.

Galas

Date picked

Firmness (pounds)

Starch

Brix

8/26/2015 - Average

23.0

1.2

11.0

9/1/2015 – Average

22.4

2.5

12.0

9/8/2015 – Average

20.3

5.4

13.0

9/14/2015

18.0

7.2

13.6

9/14/2015

22.2

3.8

14.7

9/14/2015

19.0

7.0

12.8

9/14/2015 – Average

19.7

6.0

13.7

McIntosh predicted long-term storage harvest date for 2015 for central Berrien County is Sept. 6. The average target starch index this week for Mac was 4.6 compared to last week’s 3.9, with a target of 5 for good quality direct sales. Macs have generally dropped below the recommended minimum firmness for successful long-term CA storage.

McIntosh

Date picked

Firmness (pounds)

Starch

Brix

8/31/2015 - Average

16.5

3.7

12.0

9/8/2015 - Average

16.1

3.9

12.0

9/14/2015

15.4

4.6

11.0

9/14/2015

15.1

4.2

12.8

9/14/2015

16.0

5.0

13.0

9/14/2015 – Average

15.5

4.6

12.3

Honeycrisp firmness is currently averaging 15.0, down from last week’s16.1 pounds. Starch conversion moved from an average of 6.0 for last week to 6.5 this week. The predicted long-term storage harvest date for 2015 Honeycrisp for central Berrien County is Sept. 9. All three sites tested above the target starch index of 3.5 for maturity and at or below the 17 pound recommended firmness for successful long-term CA storage. Bitter pit and poor skin color are the primary problems in some orchards. Poor color seems to be associated with sites that have a thick canopy and vigorous tree growth.

Honeycrisp

Date picked

Firmness (pounds)

Starch

Brix

9/1/2015 - Average

16.9

3.0

11.3

9/8/2015 - Average

16.1

6.0

11.8

9/14/2015

14.4

7.4

12.8

9/14/2015

15.0

5.6

12.3

9/14/2015

15.6

6.4

10.9

9/14/2015 – Average

15.0

6.5

12.0

This is the second week of Empire testing. The predicted long-term storage harvest date for 2015 in central Berrien County is Sept. 18. All four sites tested below the target starch index of 3.5, but two were close. Fruit firmness averaged 17.7 pounds, about 1 pound less than last week and close to the target flesh firmness for long-term storage for some sites.

Empire

Date picked

Firmness (pounds)

Starch

Brix

9/8/2015 - Average

19.0

2.2

10.3

9/14/2015

19.0

2.0

10.7

9/14/2015

18.3

2.0

10.3

9/14/2015

16.4

3.4

10.3

9/14/2015

17.2

3.2

11.8

9/14/2015 – Average

17.7

2.7

10.8

This group of early Fuji includes the varieties Early Auvil, September Wonder, Morning Mist and Nickell. The four sites averaged 15.3 pounds and starch conversion of 6.6 pounds, testing well above the target starch index of 3.0. The relatively low firmness makes these apples suitable for short-term storage and more immediate consumption. Target starch index is 3.0 and the target firmness for long-term CA storage is 18 pounds.

Early Fuji

Date picked

Firmness (pounds)

Starch

Brix

9/8/2015 – Average

17.0

5.5

12.2

9/14/2015

16.0

4.4

12.1

9/14/2015

15.0

6.2

12.6

9/14/2015

15.3

7.8

11.8

9/14/2015

15.0

7.8

13.2

9/14/2015 – Average

15.3

6.6

12.4

This is the first report for the Jonagold variety. Fruit firmness tested 17.2 pounds with starch removal index of 4.3. Jonagold are ahead of the predicted harvest date of Sept. 23 for long-term CA storage. The target firmness for long term storage is at least 17 pounds, and recommended starch index for direct sales is 3.5

Jonagold

Date picked

Firmness (pounds)

Starch

Brix

9/14/2015

17.0

4.8

12.2

9/14/2015

17.1

5.4

12.5

9/14/2015

16.5

4.6

11.1

9/14/2015

18.0

3.8

11.6

9/14/2015

17.4

3.0

12.8

9/14/2015 – Average

17.2

4.3

12.0

This is the first report for the Jonathan variety. Fruit firmness this week tested 18.6 pounds with starch removal index of 3.6. It appears that Jonathan are maturing ahead of the predicted harvest date for long-term storage of Sept. 23 for Berrien County. Golden Delicious has a target firmness of at least 16 pounds for long-term CA storage and minimum starch index of 3.5 for more immediate successful direct sales.

Jonathan

Date picked

Firmness (pounds)

Starch

Brix

9/14/2015

18.3

3.6

12.4

9/14/2015

20.0

3.0

11.4

9/14/2015

19.2

4.0

12.1

9/14/2015

17.0

3.6

12.9

9/14/2015 – Average

18.6

3.6

12.2

This is the first report for the Golden Delicious variety. Fruit firmness this week tested 18.6 pounds with starch removal index of 1.8. Golden Delicious has a predicted harvest date for long term storage of Sept. 28 for Berrien County. Golden Delicious has a target firmness of at least 17 pounds and starch index of 3 for successful long-term CA storage. Goldens are not at the point for picking for long-term CA storage for fresh sales.

Golden Delicious

Date picked

Firmness (pounds)

Starch

Brix

9/14/2015

18.1

1.6

11.9

9/14/2015

17.3

2.2

12.9

9/14/2015

19.0

2.2

11.7

9/14/2015

20.0

1.0

11.4

9/14/2015 – Average

18.6

1.8

12.0

This is the first report for the Red Delicious variety. Fruit firmness this week tested 17.9 pounds with starch removal index of 2.3. Red Delicious has a target firmness of 18 or more pounds and starch index of 2.5 for successful long-term CA storage. It appears this variety is running ahead of the predicted harvest date of Oct. 4 for Berrien County for long-term CA storage.

Red Delicious

Date picked

Firmness (pounds)

Starch

Brix

9/14/2015

16.5

3.4

10.0

9/14/2015

19.0

2.2

9.1

9/14/2015

18.0

2.0

8.5

9/14/2015

18.2

1.6

9.9

9/14/2015 – Average

17.9

2.3

9.4

 

Table 1. 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

*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.)

Normal and 2015 peak harvest dates for varieties for the Berrien County area in southwest Michigan

Variety

Relative days -/+ Redchief

Normal date

2015 predicted date

Lodi

-60

July 23

N/A

Pristine

-55

July 28

N/A

Williams Pride

-50

Aug. 2

N/A

Gingergold

-32

Aug. 20

Aug. 20

Paulared

-30

Aug. 22

Aug. 18

Zestar

-30

Aug. 22

Aug. 18

Gala

-23

Sept. 8

Sept. 7

Early Fuji strains

-23*

Sept. 3*

Sept. 3*

McIntosh

-20

Sept. 10

Sept. 6

Honeycrisp

-15*

Sept. 13

Sept. 9

Empire

-10

Sept. 18

Sept. 18

Jonathan

-10

Sept. 22

Sept. 23

Jonagold

-10

Sept. 22

Sept. 23

Golden Delicious

-4

Sept. 25

Sept. 26

Red Delicious

0

Sept. 28

Oct. 4

Idared

+5

Oct. 5

Oct. 5

Rome

+10

Oct. 5

Oct. 5

Fuji

+15

Oct. 20

Oct. 20

Braeburn

+15

Oct. 20

Oct. 20

Goldrush

+21

Oct. 26

Oct. 26

* Indicates revised dates

The samples for these reports are collected primarily in Berrien and Van Buren counties – the maturity is only a broad indication of trends for this area. Sites north of here, closer to Lake Michigan, on heavier soils or with heavier crop loads will generally harvest later.

Contact Bill Shane at the Southwest Michigan Research and Extension Center (SWMREC), 269-944-1477 ext. 205 or 269-208-1652, if you would like to have samples from your farm tested for maturity. Statewide reports will generally be available on the Michigan State University Extension Apple Maturity page by Wednesday afternoon each week.

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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