MSU Extension

General comments

This is the third Michigan State University Extension apple maturity report from the Grand Rapids, Michigan, area fruit team. Growers in the area are busy picking several varieties like Gala, Honeycrisp, McIntosh and many others. Dry weather has allowed growers to keep up with harvest tasks pretty well. Bright, sunny days and cool, crisp nights have made for excellent coloring weather, which we haven’t had for the past two growing seasons.

From the additional sampling for this week, it seems our predicted harvest dates are still on target. The dates in the table below are guesstimates for the peak of harvest with no harvest management applied. Keep in mind that trees with a lighter crop load will tend to ripen earlier and trees with a heavy crop load will show a delay in maturity. There certainly is a wide variability in fruit set this season due to the very long, drawn out bloom period and crop losses due to freezes. If you have any questions about maturity, please let me know and I’d be happy to run a sample through our lab.

It seems that in several of our samples, fruit firmness is up slightly compared to last week’s samples. Over the years, we have noticed firmness can bounce around quite a bit week-to-week. Climate impacts firmness the most and that certainly bounces around year-to-year. Individual blocks that have irrigation or not, or rainfall variability across an area comes into play—this could impact firmness as well.

Variety sampling results for the general Grand Rapids area

Gala harvest is well underway on the Ridge and quite a few went into bins over the last week. Color has improved from 87 percent red color last week to over 90 percent red color this week (depending on strain, of course). Background color ranges in the 1 to 2 area, indicating fruits are ready for harvest. Firmness is still very good at around 20 pounds pressure, similar to last week. The starch index moved upwards from 3 last week to 3.9 this week. Brix level has improved from 12.4 last week to 13.7 this week.

Last week, I mentioned Gala were just coming into the window for long-term controlled atmosphere (CA) storage. They are there this week and we have seen many harvested in the few days. Size is good and improving a bit week-to-week. Blocks with irrigation and a moderate crop load certainly have larger Gala this year.

Nearly all fruits are over the 0.2 ppm internal ethylene mark, so ripening cannot be held back now in untreated Galas. Watch your blocks carefully and stay ahead of harvest—the warmer weather this week could move Galas along faster than expected.

McIntosh are also being harvested in between other varieties as color, time and labor allows. Macs are moving forward with 30 percent of fruits now over the 0.2 ppm internal ethylene level compared to 16 percent last week. There is some fruit drop happening, but not significant at this time. Warmer weather this week could move ethylene production forward and increase drop risk, making stop-drop applications potentially necessary.

Color is excellent on the redder strains and even very good in the traditional strains. Our samples show a slightly decreased background color averaging just below 2, which indicates Macs are still very much in the window for long-term CA storage. Pressure readings are decreased this week to 14.5 pounds compared to last week’s 15.7 pounds. Brix reading has improved nicely from 12.7 last week to 14 on average for this week. Macs eat well right now as they have lost that starchy quality.  

I mentioned in the last two reports that Honeycrisp were moving rather quickly toward maturity despite the Sept. 15 predicted harvest date. In our area Honeycrisp project, we have collected samples from over 30 orchard sites around Grand Rapids and most had not been harvested yet on Monday, Sept. 11. Harvest will begin as red color improves and the next week or so will be big harvest weeks on the Ridge for Honeycrisp.

If you are considering storage for Honeycrisp (refrigerated or controlled atmosphere), using 1-MCP is highly recommended for the 2017 harvest, as they seem to be moving rather quickly through the various stages of maturity and ripeness. We are seeing increased fruit drop in some Honeycrisp blocks. This is not unusual for a high ethylene producing variety like Honeycrisp, but keep an eye on it and treat with stop-drop materials or harvest accordingly.

Watch your sites carefully and test for firmness and starch to monitor maturity block-by-block. Firmness readings are still very good to excellent at an average of 18.1 pounds, up from last week. Starch readings continue to be variable as is typical for Honeycrisp, but we now see readings ranging from 5 to 8 with no fruits in the 1 to 2 range. The average starch is 6.6 this week compared to 5.9 last week. Brix level improved from 13.1 last week to 13.8 this week.

Honeycrisp are eating better every day. Bitter pit still seems to be low overall, but some blocks with lighter crop load and very large fruits have increased bitter pit symptoms this week.

Empire were sampled for the second week and they have moved forward in maturity a bit, but are still immature overall. Color is about the same at 68 percent red color this week compared to 70 percent last week. The background color has changed little from last week. Fruit firmness is down slightly from 21 pounds last week to 17.6 pounds this week. The starch index readings were 1s and 2s last week and are all 2s this week, so only a slight change. Brix has improved from 11.6 last week to 12.8 this week.

I haven’t tasted an Empire yet, and I really want to—it’s my favorite apple variety. I’m sure they are very starchy to bite into; maybe I’ll be brave by the end of the week to try one. The predicted peak harvest date for Empire is Sept. 25, which is about the normal date for Empire harvest in the Grand Rapids area. That might be a little on the late side—next week’s sample will really tell us what’s going on with Empire and how accurate our date is.

Jonathan continue to be immature according to the maturity indices we observe, but they have moved slightly from last week. The predicted harvest date for Jonathan in Grand Rapids is Sept. 27 for peak harvest. No fruits in our samples showed internal ethylene, where 20 percent did last week; perhaps the cooler weather slowed ethylene development.

Red color is excellent (our samples are RubyJon) at 97 percent red color. Background color seems very low to me and I have to wonder if our lab help cannot adequately determine the background color given such a high percentage of red color. Firmness is still very good at 16.1 pounds this week compared to 17.5 pounds last week. The starch index is up slightly from 2.6 last week to 3.2 this week. Brix levels have improved as well from 12 to 13.6 this week.

As for Empire, time will tell if our predicted harvest date is accurate—Sept. 27 is the normal average for Jonathan and Jonagold in the Grand Rapids area. With earlier varieties being a little on the early side of this average so far, maybe Sept. 27 will be a little late. Next week’s samples will tell a better story.

The maturity indices in Jonagold are very similar to Jonathan as usual. There is no internal ethylene production in our Jonagold samples. Red color is up only slightly from 29.5 percent last week to 36 percent this week. The background color is holding in the 3 to 4 range. Fruit firmness is excellent at 21.1 pounds. Starch index improved slightly from 2 last week to 3.2 this week. Brix level is improving as well at 12.9 this week compared to 11.8 last week.

Golden Delicious have a predicted harvest date of Oct. 1 for the general Grand Rapids area. Our samples this week showed very little changed compared to last week, and Goldens are still very immature. There are still no fruits with internal ethylene over the climacteric of 0.2 ppm. They are very green with a background color of 4.1 on average compared to last week’s 4.5. Pressure is excellent at 22 pounds.

There is very little starch clearing, but there was a slight improvement from 1.3 last week to 2.6 this week. Brix are pretty good at 12.4, but have only to improve over the next two weeks. While we praise the great coloring weather for most varieties, in Golden Delicious the cool nights and sunny days are adding a little pink cheek.

Next week, we will continue sampling all the varieties listed above and add a few more.

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