Northwest Michigan apple maturity report – Sept. 6, 2017

Despite the beautiful color on apples, don’t be overly eager to start fall apple harvest.

A rainbow added to the beauty of harvest this week in Northwest Michigan. Photo credit: Nikki Rothwell, MSU.

A rainbow added to the beauty of harvest this week in Northwest Michigan. Photo credit: Nikki Rothwell, MSU.

General apple harvest comments

This is the second apple maturity report of the 2017 season. Gingergold harvest is ongoing at this time, and growers with SweeTango began picking in the last week. In addition to one sample of Gingergold, we tested the varieties McIntosh, Gala, and Honeycrisp. Apple maturity tests show that these fruit are moving in the right direction, but they are not ready for harvest yet. With the excellent color on most varieties, particularly for the beginning of September, growers might be eager to start fall apple harvest. However, our starch index readings are still in the 1-2 range, and firmness is 19-22lbs. Brix levels also seem good for this time of the year especially with all of the rain we have received across the region.

The Enviroweather station at the Northwest Michigan Horticulture Research Center recorded nearly an inch of rain since Monday, Sept. 4, and other Northwest Lower Michigan stations are recording well over an inch of rain. There is also more rain in the forecast for the remainder of the week. Excess rainfall later in the season could pose challenges, such as increases in bruising during picking. In past seasons, we have also observed cracking in the stem bowl in Galas and Honeycrisp, but we have not seen cracking yet this year. More importantly, Michigan State University Extension advises that for diseases and rots, particularly for apples that will be stored, use a late season fungicide application following this recent rain to minimize disease development. The fungicide Pristine is a good choice at this time.

We have had reports of hail with the recent heavy rains, but we have not observed damage as a result of this weather. Last night, Sept. 5, we had some great rainbows across the region.

Apple maturity in southwest Michigan for apples harvested Aug. 29

Variety

Firmness lbs. (range)

Starch (range)

Brix %

Gingergold

19.1

2.2

12.4

McIntosh

19.4 (18.1-20.5)

1.7 (1-2.2)

10.3

Gala

21.9 (20.4-22.6)

1

10.0

Honeycrisp

21.1 (19.7-22.7)

1.6 (1-2.8)

11.1

Individual variety results

Gingergold maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 30

19.7

1

11.8

Sept. 5

19.1

2.2

12.4

Some growers of Gingergold have wrapped up harvest of this variety, but there are a few blocks remaining that have yet to be harvest. These apples have maintained their firmness over the last week. Brix percentages have continued to improve and starch indices have risen. This variety tastes and looks great this season.

McIntosh maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 30

18.6 (18.5-18.6)

1.1 (1.0-1.2)

9.7

Sept. 5

19.4 (18.1-20.5)

1.7 (1-2.2)

10.3

McIntosh apples have continued to color up nicely over the last week, and maturity test results show that these apples are moving along with increases in brix percentages and starch conversion. Firmness is holding up nicely at this time, and these results are promising for apples that will be stored. We have observed some fruit pushed off the tree, but fewer than in past seasons.

Gala maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 30

21.2

1

8.8

Sept. 5

21.9 (20.4-22.6)

1

10.0

Gala apples are also showing nice color, and size on Gala in most blocks is excellent compared with past seasons. Other than increases in brix percentages, there has not been much movement in ripeness since testing last week. These apples have several weeks before they will be ready to eat fresh—starch index on our samples are still reading about 1.

Honeycrisp maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Aug. 30

19.5 (18.9-20.1)

1.3 (1.0-1.6)

10.7

Sept. 5

21.1 (19.7-22.7)

1.6 (1-2.8)

11.1

Honeycrisp are not ready for picking, but brix percentages increased this week and we observed slight increases in starch indices. Pressures also remained high, and most blocks have nice color.

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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