Northwest Michigan apple maturity report – Sept. 30, 2020

A rainy week will slow harvest. Growers are finishing up with Gala and many are harvesting Honeycrisp.

General apple harvest comments

Growers are moving along through the 2020 harvest. Many Gala and McIntosh blocks are finishing up, and the quality remains good despite some bad weather over the weekend. There were reports of hail damage in some blocks from a storm on Saturday morning 26 September, but overall, the damage seems minimal. We received 0.77” of rain at the NWMHRC that Saturday and another 0.55” on Monday, 28 September. Some other Enviroweather stations received more rain on these days and other received less; all stations recorded some level of rainfall on these two days. More rain is predicted for today, (Wednesday 30 September) Wednesday, and Thursday (1 October), and these rains could slow apple harvest if the amount of rainfall is going to be high as anticipated. The chance of rainfall will decrease as we approach the weekend, but wet weather is predicted on and off for the next five days. Weather will also be cool, both in the daytime with highs reaching into the 50s and lows in the low 40s. Rain and cool temperatures will make harvest challenging over the next few days. 

Thus far this season, we have accumulated 3545 GDD base 42 and 2375 GDD base 50. The warm conditions moved ripening along quite a bit last week. Our Honeycrisp starch removal index was only 1s and 2s last week, and our samples from the NWMHRC this week showed a big jump into the 4s and 5s, with even some at 6s or higher. Brix also jumped in this variety after the warm conditions. Many growers are just beginning Honeycrisp harvest because the fruit was still eating a bit on the green side later last week. There have been some reports of bitter pit in Honeycrisp, but the overall incidence has been manageable this year. Color on all varieties is excellent, and size is also good. Growers have been particularly pleased with size of Gala as sometimes we struggle to size this variety in our lighter soils. Gala quality at the NWMHRC has been excellent with great color and flavor. We had a light crop of Honeycrisp at the NWMHRC, and as a result have more bitter pit than commercial growers. 

Catches of brown marmorated stink bug (BMSB) are going up at the NWMHRC and at grower sites this week. We are using different traps (i.e. pyramid traps similar to those used for plum curculio and sticky panel traps) to monitor for BMSB at the station and grower sites as part of a collaborative research project. At the NWMHRC, we caught six adult males and three adult females for a total of nine BMSB on a pyramid trap, and one male and two females for a total of three BMSB on the panel trap. We caught one male BMSB at a grower site in Leelanau County. Late last week, we also caught two males, one female, and one nymph on a panel trap at a grower site in Antrim County. 

This summer was the first time that we detected BMSB on traps placed adjacent to orchards in northwest Michigan. While we have observed this pest outside of the orchard in years past, we had not found them in our traps along orchard edges until this season. Since our initial detection on 24 August, we have trapped this pest every week at the station and trap catches in the region seem to be on the rise. However, our regional catches of this pest are still low compared with other regions of the state. For example, some traps in SW Michigan are catching BMSB in the hundreds. We have not observed nor received reports of BMSB damage on fruit at this time. Growers are encouraged to look for potential BMSB damage on fruit, especially along orchard edges near woodlots and field crops that may be hot spot locations. We will continue to trap until later in the season to see how the numbers change over time. 

Apple maturity in northwest Michigan for apples collected on Sept. 29, 2020

Variety

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

McIntosh

99.0%

16.9

4.3

11.3

Honeycrisp

78.6% (50-100)

17.4 (15-21)

5.0 (3-6)

12.3 (10-16.2)

Gala

97% (95-100)

19.9 (15-22)

3.6 (2-8)

13.2 (11-16.8)

Jonagold

95% (60-100)

17.7 (17-22)

5.6 (2-7)

13.2 (12-13.7)

Ida Red

70%

19.8

1.7

11.2

 

McIntosh maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 1, 2020

83% (60-100)

18.9 (16-22)

1.1 (1-1.5)

10.25 (9.6-11)

Sept. 8, 2020

88% (60-100)

18.7 (14-23)

1.8 (1-4)

11.1 (9-12)

Sept. 15, 2020

81% (40-100)

17.2 (14.5-20.5)

3.0 (1-6)

11.5 (10.8-13)

Sept. 22, 2020

90% (75-100)

17.3 (14.5-22.5)

3.8 (2-6)

11.9 (11-13.9)

Sept. 29, 2020

99.0%

16.9

4.3

11.3

McIntosh harvest is winding down, but we found one block to sample this week. The apples are beautiful, and all parameters suggest that these apples are at the ideal timing for fresh eating.

Honeycrisp maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 1, 2020

41.3% (15-70)

19.2 (16-23)

1.0 (1-1.5)

10.0 (8.6-10.8)

Sept. 8, 2020

51% (5-95)

18.6 (16-22)

1.2 (1-2)

10.4 (8.8-11.4)

Sept. 15, 2020

72.3% (50-95)

18.4 (15-22)

2.0 (1-4)

11 (9.8-12.6)

Sept. 22, 2020

74.3% (50-95)

18.0 (15-22)

2.7 (1.5-5) 

11.6 (10.1-13.7)

Sept. 29, 2020

78.6% (50-100)

17.4 (15-21)

5.0 (3-6)

12.3 (10-16.2)

Growers are harvesting Honeycrisp, and our maturity tests indicate that it is time to harvest this variety. We sampled six Honeycrisp blocks this week; firmness is decreasing, Brix is increasing, and starch indices jumped up from an average of 2.7 to 5.0 this week. While there is some variability in maturity among the apples that we sampled, on average, most orchards are ready for harvest. 

Gala maturity sampling for the harvest season

Sample date

Color % (range)

Firmness lbs. (range)

Starch (range)

Brix %

Sept. 8, 2020

82% (20-100)

21.3 (17-23)

1.9 (1-7)

11.2 (9-14.6)

Sept. 15, 2020

88% (60-100)

21.2 (17.5-23)

1.5 (1-4)

11.3 10-13)

Sept. 22, 2020

95% (90-100)

21.4 (17.5-23)

1.4 (1-3)

11.6 (10.1-13.5)

Sept. 29, 2020

97% (95 - 100)

19.9 (15-22)

3.6 (2-8)

13.2 (11-16.8)

Three blocks of Gala were tested this week, and Gala harvest is winding down. There is variability in maturity among apples, likely due to the different strains of this variety. Generally, Gala are still firm with good Brix, and starch indices that are right on target for harvest. However, there are a few apples in the samples with high starch readings indicating that some apples are becoming overmature. We are also observing apples with stem-end cracks at the station; we have heard similar reports from our colleagues across the state. Color continues to be excellent on this variety. 

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)

Three Jonagold samples were taken this week; there was only one Jonagold sample taken previously which helps to explain why color appears to be decreasing. Overall, the apples are still firm, but firmness is decreasing and Brix has improved since last week. Starch readings indicate that they apples are mature and ready for harvest. 

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

One sample of Ida Red was tested this week. Firmness is decreasing and starch indices are increasing. However, this variety is not yet ready for harvest.

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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