Grand Rapids area apple maturity report – October 9, 2013

Apple growers are over the hump when it comes to harvesting on the Ridge.

General comments

Harvest is one of the most stressful times for apple growers and especially so this year. So to start my report on a positive note, I wanted to point out that you are over the hump. Since growers are in the midst of harvest on the Ridge right now, it might not be apparent to them that we estimate just over 50 percent of the total apple crop is now off the trees for the Ridge. It looks as though the great fall weather will continue after a few days of rain last weekend.

Now for the not so positive: Lack of labor overall and so many hired hands new to picking apples continues to keep harvest at a slower pace than you might have experienced two or three years ago. Growers need to take a hard look at what still needs to be picked and compare that to the possible number of days left for harvest this fall. Some hard decisions about what to go after and what to try to get to later might need to be made. You need to take into consideration current markets for the varieties you have left to pick as well. For instance, I’ve heard that some are leaving Jonathans to get to other varieties and hoping to come back to Jonathans when time and help allows. Focusing on what you have control of and moving forward is a good tactic to reduce stress levels.

Summary of Grand Rapids, Mich., apple maturity samples taken Oct. 7, 2013


Avg. Ethylene (ppm)

% Fruits with Ethylene over 0.2 ppm

Color % (range)

Firmness lbs pressure (range)

Starch (range)

Brix (range)

Red Mac



97 (95 -100)

11.4 (8 - 15.5)

6.2 (5 -8)

14.5 (14 - 15.5)




67 (35 - 95)

12.4 (10 - 16.2)


12 (11 - 13)




60 (20 - 90)

15.4 (13.2- 19.1)

6.8 (6 - 8)

12.6 (11 - 13.5)

Golden Delicious




13.9 (12.2 - 18)

6.3 (4 - 7)

11.5 (10.5 - 12)

Red Delicious




15.2 (11.5 - 18.5)

1.7 (1 -2 )

12.6 (11 - 13)

Ida Red



74 (30 - 95)

15.2 (13.2 - 17.5)

2.1 (1 - 3)

12.3 (11.5 - 13)




54 (30 - 80)

17.9 (15.6 - 21.5)

4.5 (1 - 8)

13.3 (13 - 14)





19.9 (17.6 - 21.6)

3 (2 - 6)

12.9 (12.5 - 13)


Macs are 99 percent finished for the Ridge, but there were a few around that were not treated with ReTain for us to get a sample from this week. All maturity numbers indicate that McIntosh are in a short-term CA storage window or fit for direct retail sales. It’s somewhat surprising that internal ethylene is not higher this late in the McIntosh harvest window – perhaps the remaining fruits were mostly from the inside of the tree waiting for color and their maturity is behind the average. There were some McIntosh blocks with quite a bit of fruit drop last week where labor was short.


Honeycrisp harvest is over for the most part with only fruit hanging for U-pick and those with on-farm markets. All maturity indices show that Honeycrisp are very mature.


We did not find blocks to sample from this week, but Empire is most likely in the mid- to short-term CA window for the Ridge and mid-term CA for Hart, Mich., and Ludington, Mich.


Quite a few Jonagolds have been picked in the last seven days and the Ridge is well over half-way done with harvest of this variety. Maturity indices show 40 percent of fruits over 0.2 ppm, the same as last week, with the average internal ethylene higher than last week. Overall, Jonagold continues to move slowly through maturity stages and untreated fruits are in the mid-term CA window right now on the Ridge. Firmness is down to 15.4 pounds this week from nearly 18 pounds last week; starch is up to 6.8 on average, increased as expected from 5.9 last week; and brix levels have increased slightly to 12.6 this week compared to 12.1 last week.


Maturity numbers for Jonathan are very similar to Jonagold with a good number of Jonathans in storage now. Any fruit still hanging with no harvest management materials applied are in the mid-term CA window. Some blocks are being left for the time being to get to other varieties with known markets. There is quite a bit of uncertainty around Jonathan this year as processing prices are still in limbo.

Golden Delicious

The predicted harvest date for Golden Delicious was Oct. 2 and they were ready for long-term CA storage at that time and have now moved into a mid-term CA window. There are quite a few Golden Delicious left to be harvested on the Ridge. Internal ethylene is still very low with only 20 percent of fruits with levels over 0.2 ppm. Fruit firmness is a concern at only 13.9 pounds on average and you can tell when picking some blocks that the fruit is softer than desired and bruising is an issue. Starch clearing shows mature fruits at 6.3 on average. Brix are OK at 11.5 on average, but not as high as expected. Due to lack of fruit firmness in some Golden Delicious, it is guesstimated that they will quickly move out of the CA storage window if not treated with harvest management products.

Red Delicious

This was the third week of testing for Red Delicious and they have finally started to make a definite forward movement in maturity compared to last week. Internal ethylene has increased from no fruits with levels over 0.2 ppm to 20 percent of fruit over that climacteric. Firmness is still very good at 15.2 pounds on average compared to 16.6 pounds last week; fruit are still very starchy at an average of 1.7 (1.9 last week), which is not unusual for Reds. Brix have improved from 11.5 last week to 12.6 this week. The predicted harvest date for Red Delicious was Oct. 5 and from the data this week, that date was probably a bit early for long-term CA storage. You know your Red Delicious strains and blocks better than anyone else, so harvest accordingly now that the long-term CA window is just opening for this variety.

Ida Red

The predicted harvest for Ida Red was estimated for Oct. 10. Fruit sampled this week indicates that this is a good date to target harvest for long-term CA storage on the Ridge. Internal ethylene is up a bit this week with 60 percent of fruits over 0.2 ppm compared to 40 percent last week. Fruit firmness is down just a little from 15.8 last week to 15.2 this week. Starch clearing is 2.1, which is similar to last week’s 2.3 average. Brix levels have increased from 10.9 last week to 12.3 this week. As time and labor allows, growers should get started on Ida Red in the next week.


Rome was sampled for the first time this week and all levels still indicate immature fruits. The predicted harvest date for long-term CA storage is Oct. 15 and that will be a good date to target for the Ridge. Hart, Mich., and Ludington, Mich., should be about three to seven days after that. Only 20 percent of fruits had internal ethylene over 0.2 ppm. Fruit firmness is 19.9 pounds as expected for Romes at this time. Starch clearing averages 3 and brix levels are very good at 12.9. Rome is still immature at this time, but there is some harvest going on for long-term storage for processing.


We sampled a regular late harvested Fuji strain this week and while some of the numbers might indicate this variety to be nearing the long-term CA window, they still eat very starchy and the predicted harvest date of Oct. 25 is probably adequate. We will know more when we sample next week, but fruits are very hard at nearly 20 pounds pressure with starch clearing at 3, which is a bit higher than expected and brix levels are pretty good for this early at 12.9. So, while the numbers don’t exactly indicate immaturity at this time, there should be no hurry to get to fall Fujis for at least 10 days from 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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