Grand Rapids area apple maturity report – September 25, 2013

Harvest is well underway with excellent apple quality.

General comments

In the Grand Rapids, Mich., area, harvest of Gala and Honeycrisp is wrapping up this week. Cortland, early Fuji strains and McIntosh are mostly harvested. Some recent rainfall has helped with fruit size and the cooler nights and bright, sunny days are really helping to develop flavor and color.

Labor continues to be tight and different growers have different situations. At this point, it does not appear that the low labor situation will result in apples not being harvested, but it is slowing harvest in some situations.

Keep in mind that we sample fruit until the window for long-term storage begins and that we only consider fruits that have not been treated with ReTain, NAA or Harvista. If you use these harvest management tools, you need to take that into consideration for your harvest plans.

Summary of Grand Rapids apple maturity samples taken Sept. 25, 2013


Avg. Ethylene (ppm)

% Fruits with Ethylene over 0.2 ppm

Color % (range)

Firmness lbs pressure (range)

Starch (range)

Brix (range)





16.2 (13.2 - 18.4)

7.3 (4 - 8)

14.6 (14 - 15)




96% (95 -100%)

15.6 (13 - 19)

4.2 (2 -7)

12.1 (11 - 13)




75% (50 - 95)

15.4 (13 - 18.2)

5.6 (4 - 7)

12.6 (12 - 13)




87% (75 - 95)

18.1 (16 - 20.5)

2.3 (2 - 3)

11.9 (11 - 12.5)




99% (95 - 100)

15.4 (13.8 - 18.2)

3.9 (3 - 5)

12.3 (12 - 13)

Red Delicious



97% (90 - 100)

16.8 (15 - 18.4)

1.1 (1 -2)

11.2 (11 - 12)

Ida Red



68% (40 - 80)

17.7 (15.5 - 20.2)


11.7 (11 - 12)


Gala untreated with harvest management aids are moving into the short-term CA storage window, which is indicated by the increase in internal ethylene and a decline in fruit firmness from last week to this week. Firmness is decreasing as expected from 17.7 pounds last week to 16.2 this week. Starch clearing is greatly increased from 4.8 last week to 7.3 this week. Brix are greatly improved from 12.1 last week to 14.6 this week. All these numbers indicate Gala are now at a short-term CA storage window and they need to be harvested soon if not treated with harvest management products.


Most Macs have been harvested on the Ridge. All maturity measurements indicate that McIntosh are in a mid-term CA window now and will quickly move to the short-term CA storage range. Cool weather this week will most likely start to increase ethylene quickly and start the chain of events that cause fruit to drop, so don’t wait too long to get Macs off.


Honeycrisp harvest is well underway with second pickings taking place. Fruit color still leaves something to be desired and is slow to develop this year.


This week’s sampling shows significant movement in maturity levels. Color is improved; firmness is down a little from 19.1 last week to 18.1 lbs this week; starch clearing is still between 2 and 3 and brix is improved from 10.9 to 11.9 this week. All numbers indicate that Empire is just ready for long-term CA storage and will be for another week or so before moving to a mid-term CA storage window.


Sampling this week was from Ruby Jons, so color is excellent. There were a surprising number of fruits with internal ethylene over the 0.2 ppm indicator – 40 percent - indicating a definite move in maturity for Jonathan. Fruit firmness averages 15.4 lbs and starch clearing is 3.9. Brix levels are really good at 12.3. The predicted harvest date of Sept. 28 or 29 is a good target for early harvest of Jonathan for long-term CA storage.

Golden Delicious

We forgot to sample Goldens this week. The predicted harvest date is Oct. 2 and that will be a good target for the majority of Golden Delicious harvest. There is some harvest already being done on blocks with a light crop. Retailers are complaining about the blush on Goldens - too bad, because they really are pretty this year.

Red Delicious

Red Delicious was tested for the first time this week and are still immature. Internal ethylene shows 50 percent fruits over 0.2 ppm, which is not unusual for Reds. Firmness is very high at 16.8 pounds; fruit are very starchy at an average of 1.1 and brix are very low at 11.2. The predicted harvest date for Red Delicious is Oct. 5 and from these first samples that date will be about right or perhaps a bit early.

Ida Red

The predicted harvest for Ida Red was estimated for Oct.10. Fruit sampled this week is solidly immature and at least two weeks from the long-term CA storage window.

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

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