Northwest Michigan apple maturity report – Oct. 7, 2020

Honeycrisp harvest is wrapping up and growers are moving onto later varieties. There have been a lot of big trucks with apple boxes headed south in recent days.

Starch clearing on Fuji apples
Starch clearing on Fuji apples tested Oct. 6, 2020. Photo by Emily Pochubay, MSU Extension.

General apple harvest comments

Growers are moving through the 2020 harvest season despite the wet weather we have been having for the past week. Isolated hail events were also reported in the region and across the state last week and the extent of damage is variable in areas where hail was reported. Fortunately, the hail events were not widespread.

This week is predicted to be drier and a bit warmer, which will be good conditions for growers to wrap up harvest of the area’s major varieties. Growers are finishing Honeycrisp harvest and have been pleased with color and firmness. Because most of the blocks where we collect Honeycrisp samples have been harvested, we did not test that variety this week. We harvested Honeycrisp on Monday, Oct. 5, at the Northwest Michigan Horticulture Research Center, and unfortunately our quality was not great as we had a light crop and a fair amount of bitter pit. As we reported earlier this season, bird damage was also especially noticeable while harvesting at the station.

Many growers are moving onto later ripening varieties and processing blocks. We had a great growing season and fruit are ripening well. Some growers have commented that they will ripen Evercrisp, a later variety, here in the north. Some years, we do not have the growing degree day (GDD) accumulations to optimally ripen later varieties. This season’s warmer weather has been excellent for apple harvest this fall. Fruit quality remains excellent. Size, color and flavor are all terrific.

Throughout this harvest season, we have not observed much internal fruit injury (i.e., watercore, browning, chill injury, etc.) while sampling. However, watercore has been a concern in other parts of the state. While we often think of bright and sunny days with cool nights being good conditions for ripening and coloring fruit, these conditions can also contribute to watercore development on sensitive varieties when nighttime temperatures are too cold. Fortunately, thus far the northwest region has not dipped down into the cold temperatures that can be conducive for watercore development. There are several other factors that also influence watercore development and “Watercore in Apples: Causes, concerns, detection and sorting” by Michigan State University’s post-harvest fruit physiologist, Randy Beaudry, provides more insight on the causes and concerns of watercore.

Despite changing lures in our traps last week, we did not find any brown marmorated stink bugs (BMSB) in our traps at the Northwest Michigan Horticulture Research Center this week. We will continue to monitor traps on growers’ farms in the region through the remainder of the week. We hypothesize that the cooler weather conditions may have slowed down BMSB activity.

Apple maturity in northwest Michigan for apples collected on Oct. 6, 2020

Variety

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Jonagold

82.5% (50 - 100)

19.2 (15.5 - 22)

5.6 (4 - 8)

14.5 (12.5 - 15.5)

Ida Red

91% (60 - 100)

19.4 (17 - 22)

3.4 (3-5)

12.3 (11.3 - 12.9)

Macoun

85%

16.9

4.7

12.7

Empire

84%

17.3

4.7

12.2

Fuji

87.0%

18.9

4

14

Individual variety results

Two Jonagold samples were taken this week and maturity parameters were more variable than expected between the two farms. Some apples have beautiful color while others could use some color improvements. Overall, the apples are still firm but firmness is slowly decreasing. Starch indices are increasing and Brix readings are excellent. The apples are delicious and ready to harvest.

Jonagold maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 15, 2020

90%

19.2

1.8

11.2

Sept. 22, 2020

93%

19.0

2.2

12.8

Sept. 29, 2020

88.2% (60 - 100)

18.7 (17-22)

4.4 (2-7)

13.0 (12-13.7)

Oct. 5, 2020

82.5% (50 - 100)

19.2 (15.5-22)

5.6 (4-8)

14.5 (12.5-15.5)

Two samples of Ida Red were tested this week. Firmness is continuing to decrease and starch indices are increasing with some apples an index of 5. Brix readings and color are also improving. Ida Red are eating well but are still slightly starchy.

Ida Red maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 22, 2020

82%

21.8

1.1

11.4

Sept. 29, 2020

70%

19.8

1.7

11.2

Oct. 5, 2020

91% (60-100)

19.4 (17-22)

3.4 (3-5)

12.3 (11.3-12.9)

One sample of Macoun was tested this week. When we tested this variety on Sept. 22, the apples were not ready for harvest. Two weeks later, these apples are ready for fresh eating with a drop in firmness from 21.8 to 16.9 pounds, starch indices at 4.7, and 12.7 degrees Brix.

Macoun maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 22, 2020

82%

21.8

1.1

11.4

Oct. 5, 2020

85%

16.9

4.7

12.7

One sample of Empire was tested this week and this was the only sample of Empire that we have tested this season. The apples are testing mature and ready for harvest.

Empire maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Oct. 5, 2020

84%

17.3

4.7

12.2

This was the first week sampling Fuji; we tested one sample that was collected from the Northwest Michigan Horticulture Research Center’s Ellepot research trial plot. The apples are firm with starch indices at 4, and 14 degrees Brix. These apples still look a little green but they are tasting really good.

Fuji maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Oct. 5, 2020

87%

18.9

4

14

 

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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