Grand Rapids area apple maturity report – Sept. 5, 2018

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

General comments

Welcome to the first of several 2018 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 2018 predicted apple harvest dates with some indication from early varieties that peak maturity might be advanced by three to five days from these dates. 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. Also, of note for 2018 is that there seems to be a general evenness to individual fruit maturity on most varieties which is very different than in any harvest season in the past few years. Of course, there are exceptions from block to block, but the mixed maturity that we’ve had in recent years is not as prevalent for 2018. In general, the starch clearing for apple varieties sampled so far seems to be more advanced than one might expect. Keep in mind that there are many parameters to measure to pinpoint maturity for harvest and starch clearing is just one of them we measure.

Paula Red and Gingergold harvest is mostly completed on the Ridge with overall good quality being reported. Fruit color has been lacking a bit due to very few cool nights. This week will bring some better coloring weather at least for a few days. Size has been outstanding all summer and now, due to ample rainfall on the Ridge, size should not be an issue for 2018 in most blocks.

There is some Jonathan harvest underway for the taffy apple market. Gala will be ready to harvest for long-term controlled atmosphere (CA) storage in the Grand Rapids area. Some with Fulford Gala and known early sites might be ready very soon if not already. Watch your Honeycrisp closely as they seem to be moving through maturity parameters very quickly this year—there are some blocks with Honeys ready to spot pick. Macs are seven to 10 days away from major harvest.

Given the high amounts of rain some areas have received in the last two to three weeks, pay close attention to water core in varieties that are highly susceptible to it this season and harvest accordingly. It is likely to be more of an issue this year.

Sunburn is a bit more prevalent this season and not surprisingly, given the very hot temperatures and high levels of overall sunlight.

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 on most Gala strains this year and continues to improve. Size is also good to excellent. Gala have seemed to move quickly in their maturity, which is very common when there is hot and dry weather in July and August. Please watch your individual blocks very carefully.

Our predicted harvest date for Gala for peak harvest is Sept. 10. There is likely to be some early harvest started very soon in some blocks of Gala for long-term CA storage where color and size are good. We normally like to recommend a starch index of 3 for long-term storage of Gala, but if color and size are where you need them, you could pick for long-term CA storage at a starch index of 2.

Gala 2018 maturity sampling records

Date of sample

Avg. Ethylene (ppm)

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Firmness lbs pressure (range)

Starch range)

Brix (range)

Sept. 4

3.43

65

68 (10-100)

1.7 (1-3)

20.7 (15.5-25)

2.8 (1-7)

12.8 (11.5-14)

McIntosh are somewhat more delayed than expected in their maturity for 2018 with very low internal ethylene and low brix. The predicted harvest date for peak Mac harvest is Sept. 14, which might be a day or two on the late side. Be watchful in blocks with a heavy fruit set as drop could occur from fruits pushing themselves off.

Internal ethylene is present and just over the climacteric in a few fruits, but generally all samples from Macs across Michigan have very low ethylene this season. This is good given the warmer summer and should help keep drop at a minimum for the next week or so. Pressure readings are indicating very good firmness at an average of 20.7 pounds in this week’s samples. Color is good, but not yet excellent at 68% red color.

McIntosh 2018 maturity sampling records (Linda Mac)

Date of sample

Avg. Ethylene (ppm)

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Firmness lbs pressure (range)

Starch (range)

Brix (range)

Sept. 4

0.106

30

69 (55-85)

4.4 (2-5)

15.9 (14-18)

2.7 (2-3)

11.9 (11-12.5)

Honeycrisp is moving rather quickly toward maturity, with some fruits already in the category for early harvest for fresh (shiners). Watch your sites carefully. Firmness readings are good but not excellent (likely from all the recent rains). Starch readings are quite variable for Honeycrisp, which isn’t all that unusual. Starch clearing is much higher that than this time last year most likely due to hot weather. Brix level is good, but not yet excellent at 12.7.

Our predicted harvest date of Sept. 18 is starting to look a little too late for peak harvest of many Honeycrisp sites in the Grand Rapids area. Watch your Honeycrisp blocks closely. There is overall less mixed maturity in Honeys this year which might lessen the need to so many multiple pickings as in the past two years.

Honeycrisp 2018 maturity sampling records

Date of sample

Avg. Ethylene (ppm)

% Fruits with Ethylene over 0.2 ppm

Red color % (range)

Background color (range)

Firmness lbs pressure (range)

Starch (range)

Brix (range)

Sept. 4

6.3

83

43.5 (10-75)

3.5 (2-5)

15.1 (12.5-17)

5(1-8)

12.7 (11.5-14.5)

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.


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