Grand Rapids area apple maturity report – September 10, 2014

Gala apple harvest should begin on the Ridge this week.

General comments

In the Grand Rapids, Michigan area, our apple maturity samples are indicating the predicted apple harvest dates are a good guide for 2014 apple harvest scheduling. Some varieties are a little later and others are a little earlier than these dates, depending on site, soils and rootstock. Fruit color, size and finish continue to be excellent for early harvested varieties. Some Gala harvest is just beginning with its major harvest to get underway later this week. A few McIntosh have been spot harvested as well as a few Honeycrisp. Our sampling indicates McIntosh will be behind Gala this year. For the Hart/Shelby, Michigan area, growers can expect harvest dates to be behind the Grand Rapids area using this guide: along the lakeshore approximately six days behind Grand Rapids; areas inland about four days behind.

Heavy rains over the last several weeks have likely stripped foliage and fruit of cover sprays for insects and diseases. For codling moth, look at your trap numbers from two to three weeks ago and if they are over threshold, which is five moths accumulated, the eggs that were laid at that flight timing are hatching now and need to be covered to avoid late season fruit stings. Rains and humidity over the last month have flared apple scab and powdery mildew and it’s likely that fruit rots will be an issue too under such conditions. Fungicide applications now to those blocks with active scab is the best way to prevent pinpoint scab from developing in storage.

Summary of Grand Rapids apple maturity samples measured September 9, 2014


Avg. ethylene (ppm)

% Fruits with ethylene over 0.2 ppm

Color % (range)

Firmness lbs. pressure (range)

Starch (range)

Brix (range)




77 (60 - 95)

18.4 (17.5 – 19.8)

1.1 (1 – 2)

10.2 (9 - 11)




97 (95 - 100)

14.7 (12.8 - 19)

3.2 (2 -4)

10.8 (10 - 12)




48 (10 - 90)

15.5 (13.5 – 18.2)

2.9 (1 - 5)

9.8 (9 - 11)


Color is very good to excellent on Gala strains this year, and size is excellent. Gala have moved nicely towards maturity over the past two weeks and will be ready for long-term controlled atmosphere (CA) storage this week around the Grand Rapids area if color and size are adequate. Our predicted harvest date for Gala was Sept. 14 and that will be right on target for Grand Rapids in general. Blondee maturity is similar to Buckeye Gala and these earliest harvested strains of Gala are expected to be at optimum long-term CA condition in a few days.

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 of 2. Our samples showed starch clearing has started and is up a bit from a solid 1 last week to an average of 1.1 this week – not a great increase, but a sign of movement to maturity and an indication that Gala will be ready for long-term CA storage by the end of this week or early next week.

Only 20 percent of fruits sampled showed ethylene over the climacteric of 0.2 ppm, which indicates immaturity and all individual fruit ethylene levels are increased over last week’s samples. Pressure has declined slightly from 18.5 pounds to 18.4 pounds. Brix levels improved from 9.7 last week to 10.2 this week.


Good forward movement towards maturity in McIntosh and they are getting close to long-term CA storage in the general Grand Rapids area. Our predicted optimum harvest date for McIntosh is Sept. 19 and the maturity numbers indicate that McIntosh will be ready behind Gala this year, which is quite common after a cooler summer. Ethylene continues to read low with no fruit over 0.2 ppm. Pressure readings are indicating good firmness at an average of 14.7 pounds of pressure, down slightly from last week’s 15 pounds.

Color is excellent of course on Ruby Mac and very good in other McIntosh strains and improving every day – the background color is still quite green. Brix reading is only slightly improved – 10.8 this week compared to 10.7 last week – this is not unusual for McIntosh. Pressure is very high at 18.4 pounds. Starch clearing is up slightly from 3 last week to 3.2 on average this week. Harvest for long-term storage of McIntosh can begin at any time color is right, and you have time around Gala harvest.

The majority of McIntosh harvest is 10 days away. Our predicted harvest date for McIntosh is Sept. 19. Be watchful in blocks with a heavy fruit set as drop could occur from fruits pushing themselves off. McIntosh appears to be one to two days behind Gala and one to two days ahead of Honeycrisp.


Overall slow movement towards maturity and there are a few fruits that are near ready. Our predicted Grand Rapids area harvest date is Sept. 22, which will be the optimum window for widespread Honeycrisp harvest for fresh sales. At this time, only spot-picking is recommended. The majority of Honeycrisp are not physiologically ready for harvest in the Grand Rapids area – being economically ready is a different story, with a bitter ending if done too soon. They are just beginning to spot-pick Honeycrisp in southwest Michigan and we are five to seven days behind that area.

Firmness readings are good to excellent at 15.5 pounds pressure on average, which is down a bit from last week’s 15.9 pounds. Starch readings have moved from 1.4 last week to 2.9 this week and brix are up slightly from 9.5 to 9.8 this week, which is quite low for Honeycrisp. Initial first picking of Honeycrisp for fresh sales is recommended five to 10 days from now in the Grand Rapids area. 

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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