Northwest Michigan apple maturity report – Sept. 26, 2018

Honeycrisp harvest is moving along quickly, and some growers are finishing this variety. McIntosh and Galas are next on the list for harvest.

General apple harvest comments

Temperatures dropped today, Sept. 26, and it seemed as if fall is upon us. The weather conditions in the past week have remained more summer-like, and daytime temperatures have been in the high 60s and into the 70s; yesterday, the Northwest Michigan Horticulture Research Center Enviroweather station recorded a high of 78.5 degrees Fahrenheit.

Conditions have also been dry in the past few weeks. We had rainfall Sept. 20 and 21, and it rained again last night. So far this morning, the Northwest Michigan Horticulture Research Center recorded 0.12 inch of rain. The weather is predicted to be cooler with daytime highs in the 50s and 60s. We may see warmer temperatures early next week. These conditions will be good for apples.

Overall, apple quality is looking good across the region. Honeycrisp matured quickly this season, and this variety has been the focus for harvest in the past week. We are finishing Honeycrisp harvest here at the research center and fruit quality remains quite good. Color has improved with the cooler temperatures, and the fruit is quite juicy for eating. Most growers are moving to the next variety, and a few blocks of McIntosh have been harvested. For the McIntosh samples we tested, the fruit is still starchy and still eating pretty green.

Gala is slower to mature this season, but this slower maturity has helped improve color of this variety. Some growers have had concerns with Gala size due to the dry conditions over the growing season. We tested a few other varieties and they all still need time to ripen. It seems we are into the heart of the fall season, but it is only Sept. 26, and we have a lot more apple harvest ahead.

This is the fifth 2018 apple maturity report for northwest Michigan. The following varieties are definitely moving along in maturity, but the Galas and McIntosh are still eating on the green side. However, brix levels are increasing, and the fruit tastes sweeter than last week. Fruit firmness has also decreased since we last tested these varieties. We have seen few apple pests in the past week. We can detect past damage from San Jose scale in our apples at the research center. We have had few reports of damage from brown marmorated stink bugs this season.

Apple maturity in northwest Michigan for apples collected on Sept. 25

Variety

Firmness lbs. (range)

Starch (range)

Brix

Color %

McIntosh

16.0 (15.5-16.7)

3.6 (3.2-3.9)

12.7

90.8

Gala

18.7 (18.5-18.9)

1.6 (1.5-1.9)

12.7

87

Individual apple variety results

McIntosh firmness has moved very little since last week, but we did see a jump in starch removal from 2.6 to 3.6. The brix levels are exactly what they were last week: 12.7. Color has also improved in the last week. The normal harvest date for McIntosh is Sept. 22, and from the samples we tested, this variety is not yet mature. Some McIntosh have been harvested for storage.

McIntosh maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Aug. 27

19.4

1

10.4

71.5

Sept. 4

17.7 (17.6-17.8)

1.2 (1.1-1.3)

11.3

73.8

Sept. 11

16.8 (16.6-16.9)

1.9 (1.9-1.95)

11.8

79.3

Sept. 18

16.2 (15.2-17.1)

2.6 (1.9-4)

12.7

84.3

Sept. 25

16 (15.5-16.7)

3.6 (3.2-3.9)

12.7

90.8

Gala fruit loss firmness in this past week, and brix was higher than last week. Starch indices have not changed much in the five weeks we have tested Gala. The starch removal was 1.0 on Aug. 27 and 1.6 on Sept. 25. Gala fruit are ripening slowly but again we are only at the end of September.

Gala maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Aug. 27

22.65 (22.6-22.7)

1.0

9.85

39.2

Sept. 4

21.6 (21.3-21.9)

1.03 (1.0-1.05)

10.15

54

Sept. 11

20.2 (20.1-20.3)

1 (1.0-1.0)

10.95

78

Sept. 18

20.2 (20.1-20.3)

1.1 (1.1-1.1)

11.5

89

Sept. 25

18.65 (18.5-18.9)

1.6 (1.45-1.85)

12.7

87

We tested two samples of Jonagold this week. This variety is still quite firm but less firm than we anticipated for this time of year. The starch indices were consistent between the two samples and the brix are higher than we have seen in other varieties tested this week. Color is decent at this time, but we have time for improved color before Jonagold harvest.

Jonagold maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Sept. 25

17.3 (17.08-17.4)

2.4 (2.25-2.55)

13.3

74

We tested one sample of Jonathan and this variety is still firm and has a low starch index. Color is excellent on this one sample and harvest is still a ways off.

Jonathan maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Sept. 25

18.3

1.4

12.0

96

One sample of Empire was dropped off at the research center, and our results show this sample was still firm but had a higher starch index than some other varieties tested this week: 3.2. Brix is almost 12 and color is also excellent on this sample.

Empire maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Sept. 25

18.4

3.2

11.8

94

One sample of the variety Spartan was testing firm but not yet mature. Color is also excellent on this sample.

Spartan maturity sampling for the harvest season

Date

Firmness lbs. (range)

Starch (range)

Brix

Color %

Sept. 25

18.5

1.4

12.2

96.5

 

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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