MSU Extension

General comments

This is the seventh Michigan State University Extension apple maturity report from the Grand Rapids, Michigan, area fruit team.

Growers have been steadily working on Golden Delicious, Red Delicious and Ida Red over the last 10 days. Oct. 6 and 7 brought roughly an inch of much needed rain. It had been about 30 days since the last decent rain around the Ridge and it was terribly dry. The rain cut down on the dust, but we are several inches behind our seasonal average still.

Variety sampling results for the general Grand Rapids area

Red Delicious sampling shows this variety hasn’t moved forward too quickly from last week. Readings are all right about the same. I suspect they could quickly move out of best condition for long-term controlled atmosphere (CA) storage in the next few days unless treated with a harvest management material. Our predicted harvest date for Red Delicious was Oct. 4.

Our predicted harvest date for Ida Red was Oct. 9. I thought this might be a little on the late side, but this week’s samples have not moved forward in maturity very quickly. Like Red Delicious, our sample data seems to be very similar to last week. The background color is more yellow than green from last week. Firmness is still good at 14.7 pounds, down from last week’s 15.7 pounds. Starch index is similar to last week. Brix are down just slightly, but not significant. Ida Red should be harvested now for long-term CA storage.

Cameo sampling this week shows 90 percent of fruits with internal ethylene over the 0.2 ppm climacteric—up dramatically from last week’s 20 percent. Red color is about the same at 51 percent red. The background color is down slightly to 1.3 compared to 2.7 last week. Starch readings are similar to last week at 6.6. Brix have improved from 13 last week to 14.4 this week. Cameo is now in the optimum harvest window for long-term CA storage.

Rome seems to be right on target with an Oct. 14 harvest timing. Internal ethylene is over the 0.2 ppm climacteric in 30 percent of fruits sampled. Background color had changed only slightly. Firmness is excellent at 25.2 pounds. Starch clearing is up to 5.5 from 3.3 last week, indicating a more forward in maturity. Brix are essentially the same this week. There is still very little bleeding in Romes this season. The long-term CA window is just beginning to crack open.

Fuji is once again testing my patience. Two weeks ago, I thought they would be right on target for the Oct. 24 predicted harvest date. Then a week of temperatures in the upper 80s and low 90s seemed to have moved Fuji rather quickly through their maturity. Now this week they seemed to have gone backwards for internal ethylene, red color, background color and firmness, but are moving forward in starch index and brix. Crazy Fujis—they fool me somehow every year.

With 14 days to go until our predicted harvest date, I wonder how it will turn out. Like 2016, we ended up harvesting about a week ahead of the predicted date. According to the suggested firmness and starch index levels for long-term and short-term shortage in “Checking apple maturity: What to look for” by MSU Extension, Fuji are in the window for long-term CA for firmness right now. Brix are excellent and starch is moving out of an ideal range.

Keep a close eye on your Fuji. Water core has not been much of an issue this season with dry weather conditions.

A Kiku sample was added to our work this week and it appears to be very in line with its Fuji parent or maybe slightly later. Our trees are on the young side, which could delay maturity a bit.

Kanzi is new apple variety and we don’t know that much about its maturity profile. From the fruits tested this and last week, it seems to fall right in between its Gala and Braeburn parents for maturity and should be harvested soon.

The second week of Evercrisp sampling is showing forward movement in maturity indices. We still don’t have a full picture of its maturity profile for Michigan growing conditions, but it appears to have a maturity right in the middle of its Honeycrisp and Fuji parents. Red color has improved only slightly at 51 percent compared to 42 percent last week. Background color is about the same at 3.8. Firmness is excellent at 21.9 pounds compared to 23.3 pounds last week. Brix are up to 17.2 compared to last week’s 16.5. Starch Index readings are up slightly to 4.4 on average this week compared to 3.3 last week. Keep an eye on your Evercrisp.

The second week of Pink Lady (Maslin) shows only a slight movement forward in maturity indices. Red color is up a bit to 55 percent. Background color has changed from 4 last week to 3.4 this week. Firmness is excellent at 20 pounds. Starch is still low and fairly similar to last week. Pink Lady is still immature according to the numbers and most likely will need another week or two to improve.

Braeburn has a predicted harvest date of Oct. 24 and most maturity testing still indicates immature fruits. The exception is the starch index which averaged 3.8 this week, up from 2 last week—a bit surprising for Braeburn this early. Red color and brix need some time to improve.

Granny Smith should have a harvest date similar to Braeburn and the maturity indices show immature fruit, with the exception again of the starch index being a bit higher than expected.

We will continue sampling apple varieties for at least another week or two or as fruits are available.

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