Grand Rapids area apple maturity report – Sept. 2, 2020

Early apple variety harvest is finishing up with early Gala harvest on tap for next week.

General comments

Welcome to the first of several 2020 apple maturity reports from the Grand Rapids, Michigan, area Michigan State University fruit team. As you know, 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. 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.

In the Grand Rapids area, apple maturity seems to be running close to our 2020 predicted apple harvest dates. We are seeing trends in maturity parameters showing that Gala will ripen perhaps three or four days ahead of the predictions due to the higher than normal summer heat. 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.


 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

Paula Red harvest is complete for 2020. Gingergold harvest is mostly completed on the Ridge with overall good quality being reported. Some Minnieska harvest is starting this week. Some Premier Honeycrisp harvest started this week.

Fruit finish has been surprisingly outstanding this year despite all the cool weather in early spring. Fruit color has also been better than expected with warm nighttime temperatures recently. There have been some cool nights mixed in and that must be working. Cooler weather in the forecast next week will help fruit color even more. Fruit size has been acceptable as well.

An early trend we are noticing around the state is higher than expected starch clearing readings. This is likely a factor of the summer heat and higher than normal available sunshine. Brix readings are very high. Internal ethylene is very high as well with our first samples of Gala and Honeycrisp. Fruit pressure is outstanding and higher than expected this early in the game. As stated above, all these factors and more go into the decision of when to harvest and it’s best to not rely on only one or if the seeds are brown.

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. Size is also good to excellent. Fruit pressure is outstanding. With some very warm summer temperatures, it’s looking like Gala will mature earlier than our predicted harvest date of Sept. 15. Early Gala cultivars (Wildfire, Foxtrot) are being picked as needed now. Some with Fulford Gala and known early sites might be ready very soon.

The sample readings 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

Starch (range)

Brix (range)

Sept. 1

100

97 (95-100)

1

28.1

6.7 (6-8)

14 (13-15)

Premier Honeycrisp harvest has begun where color is good. Our predicted date for traditional Honeycrisp is Sept. 23 for peak harvest.

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)

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 = measured with a Güss Fruit Texture Analyzer; range is of all fruits tested.
  • Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
  • Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

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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