Southwest Michigan apple maturity report – September 9, 2015

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

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.

General comments for this week

A string of hot days over the Labor Day weekend has accelerated apple ripening, particularly Gala, Honeycrisp and early Fuji varieties. Gala and Honeycrisp harvest is going rapidly for many orchards in the area, particularly for sandy sites. Early Fuji strains are testing relatively mature. Red skin color development has been inhibited by recent hot weather, particularly warm nights.

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

The recent hot weather has pushed Gala development. Over the last week, fruit firmness dropped 2 pounds and the starch removal index jumped from 2.5 to 5.4. Target starch index is 3. The predicted long-term storage harvest date for 2015 for 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 excellent and is sufficient for long-term controlled atmosphere (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

22.0

3.6

13.1

9/8/2015

19.4

6.2

14.5

9/8/2015

17.0

7.6

11.5

9/8/2015

22.2

3.8

12.5

9/8/2015

21.0

5.8

13.3

9/8/2015 - Average

20.3

5.4

13.0

The predicted long-term storage harvest date for main season McIntosh in 2015 for SWMREC is Sept. 6. The recent warm weather has pushed Gala maturity ahead of Macs. The average target starch index this week for Mac was 3.9, compared to the target of 5 for good quality direct sales. Macs are close to 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

16.0

4.8

13.1

9/8/2015

16.0

4.0

11.9

9/8/2015

16.3

3.8

12.4

9/8/2015

16.2

3.0

10.5

9/8/2015 - Average

16.1

3.9

12.0

Honeycrisp firmness is currently averaging 16.1 pounds, about 0.8 pounds less than last week. Starch conversion jumped from an average of 3.0 for last week to 6.0 this week. The predicted long-term storage harvest date for 2015 Honeycrisp for central Berrien County is Sept. 9. Target starch index for Honeycrisp is 3.5. All three sites tested above the target starch index of 3.5 for maturity. Selective harvesting is warranted. Blocks with significant bitter pit symptoms are not good candidates for longer-term storage as even apparently clean fruit from the same block tend to have more problems with bitter pit. Amount of fruit with symptoms range from 1 to 40 percent, depending on the orchard.

Honeycrisp

Date picked

Firmness (pounds)

Starch

Brix

9/1/2015 - Average

16.9

3.0

11.3

9/8/2015

15.2

7.4

12.3

9/8/2015

17.1

6.6

11.6

9/8/2015

16.0

4.0

11.4

9/8/2015 - Average

16.1

6.0

11.8

This is the first week of Empire testing. The predicted long-term storage harvest date for 2015 in central Berrien County is Sept. 18. All six sites tested below the target starch index of 3.5. Background color is still relatively green. Harvest can be delayed waiting for better size, brix and internal maturity.

Empire

Date picked

Firmness (pounds)

Starch

Brix

9/8/2015

19.4

2.2

9.7

9/8/2015

19.0

2.0

10.0

9/8/2015

20.0

2.0

9.6

9/8/2015

18.0

3.0

10.3

9/8/2015

18.0

2.2

11.5

9/8/2015

19.4

2.0

10.7

9/8/2015 - Average

19.0

2.2

10.3

This group of early Fuji includes the varieties Early Auvil, September Wonder, Morning Mist and Nickell. Target starch index is 3.0 and the target firmness for long-term CA storage is 18 pounds. All four sites tested above the target starch index, indicating they are suitable for consumption. Apparently we need to revise the relative harvest date to be approximately the same as Gala. This is a direct sale-type apple and probably will not be stored in refrigerated controlled atmosphere storage.

Early Fuji

Date picked

Firmness (pounds)

Starch

Brix

9/8/2015

18.2

6.8

13.6

9/8/2015

16.3

7.2

12.5

9/8/2015

15.6

4.0

11.4

9/8/2015

17.8

3.8

11.2

9/8/2015 - Average

17.0

5.5

12.2

 

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

*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

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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