Northwest Michigan apple maturity report – Sept. 13, 2017

Northwest Michigan apples are approaching maturity, but harvest is still not in full swing. Fruit quality looks excellent.

Potential boron deficiency in Honeycrisp.

Potential boron deficiency in Honeycrisp.

General apple harvest comments

This is the third Michigan State University Extension apple maturity report of the 2017 season. This week, we have seen a jump in maturity in our samples, and these results echo what growers have been seeing in their orchards. With the good color early this season, apples have seemed to mature slowly, but they are on target with the predicted harvest dates.

McIntosh and Honeycrisp varieties really moved along this week, while Gala has stayed consistent with its maturity compared to the past two weeks of testing. Based on our data, picking could begin in some blocks of these varieties sometime next week. Some growers have indicated Honeycrisp harvest will start this weekend. Take some samples of apples from your own blocks, as there is more variability in maturity between blocks this season compared to past years. We will also provide maturity testing here at the Northwest Michigan Horticulture Research Center if growers drop off the fruit—10 fruits of comparable maturity are ideal for testing. Overall, the apple crop looks good in northwest Michigan, both for quality and quantity of fruit.

Other areas of the state are reporting brown marmorated stink bug movement into orchards, which is likely influenced by the senescence of soybean crops in the landscape. We have not observed this pest in northwest Michigan at this time. Additionally, despite the excess rainfall this season and into fall, we have observed few disease issues. We do have what appears to be boron deficiency in a Honeycrisp block at the Northwest Michigan Horticulture Research Center (see photo), but we are sending tissues in for testing to confirm this diagnosis. However, overall tree health in most blocks throughout the region is also looking excellent.

Apple maturity in southwest Michigan for apples harvested Sept. 12

Variety

Firmness lbs. (range)

Starch (range)

Brix %

McIntosh

18.8 (17.2-21.6)

1.9 (1-2.4)

10.7

Honeycrisp

18.7 (18-19.3)

2.1 (1-2.7)

11.8

Gala

22 (20.8-22.6)

1

11.2

Jonagold (JonaPrince)

19.8

1

12.2

Individual variety results

McIntosh samples had variable maturity results among blocks, with some blocks having higher starch indices and others still reading fairly low on the starch index. Overall, we have observed improvements in color and brix percentages. We have not observed McIntosh pushing themselves off the tree in many blocks, and firmness appears to be holding in this variety pretty well. The predicted harvest date for McIntosh in northwest Michigan is Sept. 19, and this prediction seems fairly accurate compared with this week’s maturity data.

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

Sept. 12

18.8 (17.2-21.6)

1.9 (1-2.4)

10.7

Starch indices have remained low on Gala apples over the last three weeks. Brix percentages have increased steadily and firmness is holding well. There is color variability across blocks, but there is time for color to catch up, as these apples are not ready to be picked. Gala does seem behind other varieties for some reason this year. Growers may have to jump back and forth to different varieties this season given the variability between blocks and varieties. Growers on the Ridge have been moving from block-to-block and variety-to-variety more than in past seasons due to this season’s variability in ripeness.

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

Sept. 12

22 (20.8-22.6)

1

11.2

Honeycrisp have moved along quicker than expected in the last week, and some blocks may be ready to pick by next week. As mentioned above, some growers anticipate beginning spot-picking this weekend. Honeycrisp in four of the five blocks sampled this week had average starch indices at 2 or higher. Color has continued to improve with most blocks at above 80 percent. Honeycrisp quality looks excellent.

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

Sept. 12

18.7 (18-19.3)

2.1 (1-2.7)

11.8

We had one sample of Jonagold from Leelanau this week. Starch indices indicate this variety is not mature, but brix readings are high at 12.2; color was also excellent (98.5 percent) on this sample.

Jonagold maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 12

19.8

1

12.2

 

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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