Grand Rapids area apple maturity report – Sept. 9, 2020

Gala harvest is starting with excellent fruit color and firmness.

Woolly apple aphids in McIntosh
Woolly apple aphids in McIntosh. Photo by Amy Irish-Brown, MSU Extension.

General comments

In the Grand Rapids, Michigan, area, apple maturity seems to be running close to our 2020 predicted apple harvest dates with some of the early varieties (Gala and perhaps Honeycrisp) coming in a bit earlier than predicted. Keep in mind these predicted dates are for peak harvest, so some fruits might be ready ahead or behind these dates as we move through maturity. Many growers are saying they are picking a bit longer than expected as fruit size is excellent this year.

Some late season pests are getting in the way of harvest, woolly apple aphid in particular. There really is not much you can do this late in the season to knock them back – management should have been done in June or early July to be most effective. It is likely they overwintered quite well due to the mild 2019-20 winter. There are many beneficials in every woolly apple aphid colony I see, and they will help curb numbers for next year. I found a great resource for woolly apple aphid from Washington State University, and there are no silver bullets in it to help this late in the season.

syrphid fly adult and larva
Syrphid fly larva and adult near woolly apple aphid infestations. Photo by Amy Irish-Brown, MSU Extension.

Brown marmorated stink bug (BMSB) is also starting to make its appearance known in early apple cultivars. Damage seems to be higher than normal this season and I have noticed more BMSB in orchards than ever before. Trap numbers creep up a little every week but seeing more nymphs and adults on fruit and in trees concerns me.

bmsb on Gingergold
Brown marmorated stink bug damage on Gingergold. Photo by Amy Irish-Brown, MSU Extension.

Normal and 2020 peak harvest dates for varieties for the Grand Rapids area

Variety

Normal date

2020 predicted date

Paulared

Aug. 24

Aug. 28

Gingergold

Aug. 26

Aug. 30

Gala

Sept. 10

Sept. 14

McIntosh

Sept. 15

Sept. 19

Honeycrisp

Sept. 18

Sept. 23

Empire

Sept. 24

Sept. 28

Jonathan

Sept. 26

Sept. 30

Jonagold

Sept. 26

Sept. 30

Golden Delicious

Oct. 2

Oct. 2

Red Delicious

Oct. 5

Oct. 6

Idared

Oct.10

Oct. 11

Rome

Oct. 15

Oct. 16

Fuji

Oct. 25

Oct. 26

Braeburn

Oct. 25

Oct. 26

Goldrush

Nov. 1

Nov. 2

Variety sampling results

Strains are noted where applicable. We try our best to collect samples from blocks untreated with harvest management products.

Color is good to very good to excellent on most Gala strains this year and continues to improve. Overall size is good to excellent for Gala this fall. Fruit firmness continues to be excellent and has decreased as expected from an average of 25.7 pounds last week to 21.4 pounds this week. As mentioned last week, Gala seems to be slightly ahead of the predicted harvest date of Sept. 14 with some early harvest of the redder strains starting this week where size and maturity are in range. The sample readings in the table below are untreated fruit. Where ReTain has been used, the internal ethylene is very, very low as expected and desired.

Gala 2020 maturity sampling records

Date of sample

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Average Firmness lbs pressure (range)

Starch (range)

Brix (range)

Sept. 1

90

97 (90-100)

1

25.7 (20-34)

4.6 (1-8)

14.4 (13-16)

Sept. 7

100

94 (85-100)

1

21.4 (18-26)

4.2 (3-7)

14.2 (13-16)

The predicted harvest date for McIntosh in the Grand Rapids area is Sept. 19 and our first samples are showing that date should be accurate for the peak of harvest. Internal ethylene is very, very low with no fruits over the 0.2 ppm climacteric indicating immature fruit. Our sample is from Linda Mac so the 75% color is perhaps redder than standard Macs. The background color is very green at an average of 3.9. Fruit firmness is high at 18.3 pounds on average. Starch clearing ranges from 2 to 4 this week for an average overall of 3.9 – Macs still eat on the starchy side and really need another week on the tree, if not a bit longer. Brix readings averaged 12.7 and are quite good for Macs at 10 days from peak harvest and will surely improve.

McIntosh 2020 maturity sampling records (Linda Mac)

Date of sample

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Average Firmness lbs pressure (range)

Starch (range)

Brix (range)

Sept. 2

0

70.5 (10-95)

4

19.2 (15.5-23)

2.5 (2-3)

12

Sept. 7

0

76.5 (60-90)

3.9 (3-4)

18.3 (16-21)

3.1 (2-4)

12.7 (12-13)

Premier Honeycrisp harvest is underway where color is good. Our predicted date for traditional Honeycrisp is Sept. 23 for peak harvest. It is likely some early sites with good color will begin spot-picking of traditional Honeycrisp as early as next week, so perhaps our predicted date is a few days on the late side this year. Internal ethylene is high for Honeycrisp as usual. Red color continues to improve in our sample sites. The background color is not bad at an average of 2.5 – remember, 5 is very green and 1 is yellow. Fruit pressure is still excellent at an average of 17.5 pounds. Starch clearing has improved from 2.6 on average last week to 4.9 this week. Brix are still stuck in the 13% range and likely to greatly improve over the next 10 days.

Honeycrisp 2020 maturity sampling records

Date of sample

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Average Firmness lbs pressure

Starch (range)

Brix (range)

Sept. 1

100

62.8 (2-100)

2.5 (2-3)

21.5

4.7 (1-7)

13.6 (13-15)

Sept. 3

85

67.8 (10-100)

3.7 (3-4)

18.4 (16-21)

2.6 (1-6)

13.3 (13-14)

Sept. 7

100

77.3 (40-95)

2.5 (2-3)

17.5 (16-20)

4.9 (2-7)

13.9 (12-15)

This was our first week to look at Empire. The predicted harvest date for peak harvest in Grand Rapids is Sept. 28. This first sample shows fruit to be very immature.

Empire 2020 maturity sampling records

Date of sample

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Average Firmness lbs pressure

Starch (range)

Brix (range)

Sept. 7

0

50 (20-70)

3

20.3 (18-26)

1.9 (1-3)

12.8 (12-13)

Many changes in apple physiology occur over time as fruit become more mature—starch is converted to sugar, seeds turn a darker color, acidity decreases, chlorophyll levels decrease, respiration increases, cell walls weaken, fruit begins to soften and ethylene production increases. Our MSU Ridge Apple Quality Lab and the MSU campus Beaudry Lab measure these and many other factors to help you make harvest management decisions.

Apple maturity sampling parameters

  • % fruits with internal ethylene over 0.2 ppm = indicates when ethylene begins to influence fruit ripening and it cannot be held back easily after this is reached.
  • Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested
  • Background color: 5 = Green, 1 = Yellow; range is of all fruits tested.
  • Firmness in pounds pressure
  • Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
  • Brix = % sugar

We are graciously funded by the Michigan Tree Fruit Commission, Michigan Apple Committee, Michigan State Horticultural Society and Michigan State University Extension. Many thanks to all the growers and industry representatives that donate to our program.

Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.

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

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