Northwest Michigan apple maturity report – Sept. 20, 2017

All apple varieties are maturing with this week’s warm conditions, and apple harvest is now in full swing in northwest Michigan.

General apple harvest comments

This is the fourth apple maturity report of the 2017 season. The northwest Michigan apple crop is looking great, and growers are diving into full-fledged harvest. Maturity in all varieties is moving along quickly, and the recent warm weather has likely contributed to the speed of maturity. We are close to on target for predicted harvest dates for some varieties, but other varieties appear to be maturing faster than predicted.

This week, we have observed water core in Honeycrisp. Water core is related to maturity, and as the fruit matures, water core can increase. We also have had a lot of water this year, and with all of this available water, we may be seeing an increase in water core issues with this excess water. Lighter crops may have more water core because light crops mature earlier, and again, water core is related to maturity. If you are starting to see water core, harvest that block as soon as possible.

McIntosh and Honeycrisp varieties moved along this week, while the Gala samples we collected remained relatively unchanged except for one sample that is approaching maturity. Most growers are picking apples this week and moving to blocks that have the most advanced maturity, which is not necessarily associated with variety. Growers may foresee some challenges with managing harvest with many varieties and blocks maturing at a similar time.

The heat this week and into the weekend will also accelerate ethylene production, which will hasten maturity. Retain, NAA, and Harvista are excellent tools to help manage harvest and apple maturity, and with this warm weather, these plant growth regulators (PGRs) may have an excellent place in this year’s management programs. Please refer to “Retain and NAA as a standard practice for apples” by Michigan State University Extension’s Phil Schwallier, which outlines how Retain and NAA can be used at harvest timing. Schwallier’s updated comments on PGRs and harvest are also captured in this week’s “Grand Rapids area apple maturity report – Sept. 20, 2017.”

If you can sample from your own blocks, it will provide another layer of maturity data to be used at harvest this season. As we mentioned last week, there is more variability in maturity between blocks this season compared to past years. The Northwest Michigan Horticulture Research Center does provide maturity testing if you drop off the fruit—10 fruits of comparable maturity are ideal for testing. We conduct the testing on Tuesdays, so a Monday drop-off is preferable. Most growers are pleased with the quality of fruit across the region.

We have observed a few insects this past week, even with the warmer weather. The conditions have also been dry, so we have seen very little disease development in the orchard.

Apple maturity in Michigan for apples harvested Sept. 19

Variety

Firmness lbs. (range)

Starch (range)

Brix %

McIntosh

17.3 (16.2-18.4)

3.1 (1.2-3.9)

12.2

Honeycrisp

18.0 (17.6-18.6)

4.1 (3.0-4.8)

13.2

Gala

21.3 (20.6-21.8)

1.4 (1.3-1.8)

12.3

Jonagold

19.2 (18.9-19.5)

2.05 (1.9-2.2)

14.6

Individual variety results

McIntosh samples jumped up in maturity this week. There is still some variability in starch removal readings, which ranged from 1.2 to 3.9. However, three of the four samples had starch removal indices in the 3-range. Color in this variety also improved this week, and brix levels jumped by about 1.5 percent. For a softer variety, the McIntosh samples retained decent firmness.

Growers are harvesting McIntosh in earnest this week. 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; however, some blocks were picked last week, just before the predicted harvest date.

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

Sept. 19

17.3 (16.2-18.4)

3.1 (1.2-3.9)

12.2

Gala apple samples we have collected have not moved much from the past few weeks. We did pick samples from one block where the yellow background color is more prominent, but overall the maturity remains steady. The apples are still firm and the starch index of all four samples is only about 1.5.

The Gala variety “likes” a hot August, which really speeds up their maturity. With our cool weather during August and early September, the maturity of Gala has been delayed. With the recent warm weather, we anticipate Gala to mature this week and maturity data collected next week will provide a good indication of movement in Gala maturity. Starch removal is a good way to monitor maturity, but pay attention to the background color of Gala as an indicator of maturity.

Brix levels jumped 1 percent since last week and color is improving. Some blocks need to develop better color before harvest, and we noted considerable variability in color between different blocks. Gala size is looking good to excellent in many blocks this season.

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

Sept. 19

21.3 (20.6-21.8)

1.4 (1.3-1.8)

12.3

Again this week, Honeycrisp maturity moved quickly, and this variety is eating so much better this week. Starch index jumped up to 3 or 4, yet firmness remains at an average of 18 pounds. Brix moved only slightly since last week, and the brix averages for this week were 13.2. Color in some blocks of Honeycrisp is excellent, and others are looking better than last week. Overall color on our samples this week was 90.6 percent. Most growers have begun Honeycrisp harvest.

We have reported some water core in this variety this week, and we saw little to no water core in the samples last week.

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

Sept. 19

18.0 (17.6-18.6)

4.1 (3.0-4.8)

13.2

We had two samples of Jonagold this week. Starch indices indicate this variety is not mature, but have risen from 1 to 2 this week compared with last week. Brix jumped up from 12 last week to over 14 this week. Jonagolds remain firm.

Jonagold maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 12

19.8

1

12.2

Sept. 19

19.2 (18.9-19.5)

2.05 (1.9-2.2)

14.6

 

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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