Grand Rapids area apple maturity report – September 18, 2013

Cooler weather brings more color and flavor.

General comments

In the Grand Rapids, Mich., area, harvest of Gala and Honeycrisp is well underway. There has been a definite increase in color and flavor of these two varieties. We are noticing that in trees with a heavy crop set, the maturity is delayed a few days from our predicted harvest dates for long-term CA storage. On trees with a lighter crop load, the fruit maturity readings seem to be a bit ahead of predicted harvest dates. Growers should take this into account when trying to schedule harvest appropriately.

In general, there is some fruit drop of Honeycrisp, Gala and McIntosh, but this is mostly due to heavy crop loads and the fruit pushing themselves off the tree, rather than drop due to ethylene levels.

Summary of Grand Rapids apple maturity samples taken Sept. 17, 2013


Avg. Ethylene (ppm)

% Fruits with Ethylene over 0.2 ppm

Color % (range)

Firmness lbs pressure (range)

Starch (range)

Brix (range)




82 (40 - 95)

17.7 (13.2 - 21)

4.8 (1 - 8)

12.1 (11 - 14)




86 (60 -100)

15.6 (13 - 19)

4.2 (2 -7)

12.1 (11 - 13)




2.5 (0 - 10)

18.4 (16.2 - 20)

2.5 (1 - 5)

11.6 (11 - 12)

Red Cortland



80 (45 - 100)

15.1 (14 - 16.1)


12.3 (12 - 13)




74 (40 - 90)

19.1 (17.5 - 22.7)

2.3 (2 - 3)

10.9 (10.5 - 11)

Early Fuji



56 (45 - 70)

14.3 (13 - 15.7)

2.9 (2 -4)

12.5 (11 - 13.5)


Size and color are much improved over last week’s samples. Gala untreated with harvest management aids are moving into the mid-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.

There is some fruit cracking in Gala not treated with ReTain or Harvista. We have also heard of reports of scarf skin in Gala – Gale Gala in particular. This is a fruit finish disorder that makes the waxy surface of fruit appear milky or cloudy. Some refer to it as “opalescence.” It’s not a new problem as it was first reported in 1905. It is more severe in droughty years where there is slow fruit growth in dry spells followed by rapid fruit expansion when rains finally come. We certainly have had those weather patterns this growing season in some locations. This rapid growth after drought can also contribute to split lenticels which can lead to fruit cracking if severe. It is also thought that some fungicides can worsen the appearance of scarf skin. Scarf skin does not affect the internal quality of the fruit, but is not readily accepted in the marketplace where perfect fruit is expected.


Ethylene has made a sharp increase from this week compared to last. Color is greatly improved. Fruit firmness is about the same. Starch clearing is more prevalent and brix levels are improved. Macs are moving into a mid-term CA storage window right now and should be harvested soon.


Most Honeycrisp have had at least the first color picking done and some sites are now on the second pick. A majority of Honeycrisp should be harvested by the weekend, Sept. 21-22. Stem clipping seems to be more needed this year, especially on trees with smaller overall fruit size. We did not sample Honeycrisp this week as most need to be harvested this week.


We sampled Red Cort again this week and there is very little change in the apple maturity parameters from this week compared to last week. This variety is at least a week away from the early harvest window for long-term storage. Ethylene is very low with a few fruits being over 0.2 ppm which indicates the beginning of maturity. Color is good and firmness, starch and brix are all at immature levels this week.


This week’s sampling shows some movement in maturity, but it is not significantly different than last week’s samples. Empire is at least one week away from the window for long-term CA storage. Our predicted harvest date was Sept. 22 and that appears to be a good estimated early harvest date.

Early Fuji strains

We tested September Wonder again this week and color and brix are improved over last week. Firmness is declining and this indicates that early strains of Fuji are at least a week away from the early harvest window and perhaps two weeks away from optimal harvest for fresh market sales.


This should have been our second week of sampling Jonathan, but somehow we missed pulling this variety. The predicted harvest date of Sept. 28 or 29 is a good target. There is some harvest of Jonathan for taffy apples and the redder strains occurring now.

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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