Northwest Michigan apple maturity report — Sept. 27, 2017

Temperatures have soared into the 80s and 90s this past week, and growers are harvesting high value varieties at this time.

Brown marmorated stink bug damage to apple. All photos by Nikki Rothwell, MSU Extension.
Brown marmorated stink bug damage to apple. All photos by Nikki Rothwell, MSU Extension.

General apple harvest comments

This is the fifth apple maturity report of the 2017 season. The northwest Michigan apple crop is still looking good, and quality still seems to be holding despite this heat this past week. As with most apple growing regions around the state, the recent temperatures across northern Michigan reached into the high 80s and low 90s—Traverse City, Michigan, even broke its long standing record by five degrees on Sept. 22, when the daytime high hit 95 degrees Fahrenheit.

The temperatures have been hard on the fruit and also make harvest difficult for workers. Temperatures are predicted to cool today, Sept. 27, so we will drop from a high of 90 F yesterday to a high of 62 degrees today. McIntosh and Honeycrisp varieties again moved along in maturity this week. Many growers are concentrating on Honeycrisp right now, but McIntosh apples have been harvested this week as well. We harvested Honeycrisp at the Northwest Michigan Horticulture Research Center on Friday, Sept. 22, and again on Sept. 25, and there were noticeable declines in firmness between those three days with this heat.

We continue to observe some water core in Honeycrisp, but incidence was low in the block we tested. We also detected water core in two out of our three Jonagold samples this week. Some growers also reported sunburn in some of their blocks from the past week’s recent heat.

This week’s Gala samples range from 3.4-7.4 in starch index. This variety has matured quickly in this heat, and the Galas at the Northwest Michigan Horticulture Research Center moved from firm to extremely soft in less than five days. Growers are looking to increase their labor pool to move through harvest as fast as possible; some growers are using workers from wine grapes that are available. Growers are wondering how the apples will hold up in storage with this recent heat wave.

We have observed brown marmorated stink bug damage in many of the counties across northwest Michigan this past week (see photos). We have seen the majority of damage in Jonagold, but Golden Delicious have been a brown marmorated stink bug favorite in other areas of the state. We have also seen damage in Rome and Ida Reds. Unfortunately, we are not catching brown marmorated stink bugs in our traps, so we did not have a good indication that possible brown marmorated stink bug damage was on the horizon. The Ridge area also experienced a similar situation where they were detecting brown marmorated stink bug damage 30 days ago, and they are just starting to catch the insects in their traps this week.

If you are detecting brown marmorated stink bug damage now and still have considerable time until finishing harvest, make an insecticide application to keep the damage to a minimum. Lannate, Danitol, Actara, Lambda-Cy, Endigo and Leverage are rated excellent for brown marmorated stink bug control. Check for pre-harvest intervals as harvest is upon us.

Send pictures or drop off apples to the Northwest Michigan Horticulture Research Center and we can help you identify if the symptoms are a result of brown marmorated stink bug feeding. Feeding damage is not immediately apparent, so it is possible that when the damage appears, the culprit (e.g., brown marmorated stink bug) may not be detectable in the orchard.

BMSB damage to apple BMSB damage to apple BMSB damage to apple

Brown marmorated stink bug damage to apples.

Apple maturity in Michigan for apples harvested Sept. 26

Variety

Firmness lbs. (range)

Starch (range)

Brix %

McIntosh

19.2

1.4

12.4

Gala

20.5 (17.7-20.6)

3.7 (3.4-7.4)

13.5

Honeycrisp

17.6

4.1 (3.0-4.8)

13.0

Jonagold

18.7 (18.2-19.2)

3.6 (3.1-4.0)

14.5

Ida Red

20.3 (19.1-21.7)

1.8 (1.5-2.4)

12.4

Mutsu/Crispin*

21.7

1.9

12.2

Northern Spy*

22.8

1.4

11.7

*First sample of the season and maturity results indicate these varieties are not mature at this time.

Individual variety results

Two of the three McIntosh blocks we have sampled for apple maturity have been harvested, which was well-timed as these apples matured rapidly last week. Many McIntosh blocks across the region have been harvested. The data provided in the tables for this week’s sampling date (Sept. 26) reflects the one remaining block that has not yet been harvested. Unlike other McIntosh blocks we have sampled, the apples in this block have not matured as rapidly and continue to remain firm with a consistent starch removal index and brix percentage.

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

Sept. 26

19.2

1.4

12.4

As anticipated, Gala maturity moved quickly in the last week. Gala apples have maintained firmness despite the 2.3 increase of starch index and an additional one percent increase in brix. The apples are still firm, and the starch index of all four samples is only about 1.5. The Gala blocks we sampled this week are ready to harvest for fresh eating, and Gala at the research center are already over mature. Growers have been challenged with the overlap of harvesting Honeycrisp and Gala 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

Sept. 26

20.5 (17.7-20.6)

3.7 (3.4-7.4)

13.5

Honeycrisp harvest began last week and because maturity moved rapidly in the recent heat, many growers have shifted harvest crews to Honeycrisp blocks to get these high value apples harvested as soon as possible. Four of our five sampling sites have been harvested at this time and data for the remaining block is reflected in the table this week. This block in northern Leelanau County has reflected the trend of other blocks—a 1.3 jump in starch removal, a decrease in about 1 pound, and a slight increase in brix percentage (data not shown).

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

Sept. 26

17.6

4.3

13.0

We sampled three Jonagold blocks this week and testing results indicate most blocks are mature and ready to be harvested. Starch indices increased by about 1.5 and firmness has decreased; brix percentages are consistent with last week’s results. Water core was apparent in two of the three samples we tested.

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

Sept. 26

18.7 (18.2-19.2)

3.6 (3.1-4.0)

14.5

We sampled three blocks of Ida Red this week and there has been only a slight change in maturity since last week’s first sample.

Ida Red maturity sampling for the harvest season

Sample date

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 19

20.4

1.4

11.3

Sept. 26

20.3 (19.1-21.7)

1.8 (1.5-2.4)

12.4

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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