Grand Rapids area apple maturity report – Oct. 16, 2019

Amy Irish-Brown<irisha@msu.edu> and Philip Schwallier<schwalli@msu.edu>, Michigan State University Extension - October 17, 2019

First harvest of early blocks of Honeycrisp and Gala will begin soon.

Gala apples used for our research sampling. Photo by Amy Irish-Brown, MSU Extension.

General comments

Apple harvest in the general Grand Rapids, Michigan, area is quickly moving towards its end. Many growers tell us they will finish up in a week or 10 days. Golden Delicious are harvested and many Red Delicious blocks are picked. Most varieties in the Grand Rapids area continue to mature about four to five days or more ahead of our 2019 predicted apple harvest dates. Many growers tell us they will start with Fuji in a few days or about a week ahead of our predicted harvest date.

I’ve been keeping tabs on late season insects and the pressure is much lighter for San Jose scale, brown marmorated stink bug and woolly apple aphids this fall. In fact, I was looking in known hot spots from 2017 and 2018 for San Jose scale and couldn’t find any. The common denominator in these no-longer infected blocks was the use of Esteem IGR with oil at pink.

If you are noticing some hot spots for San Jose scale as you move through harvest, Valent, the manufacturer, tells me you could consider a fall application timing for Esteem IGR to clean up San Jose scale post-harvest instead of chasing them in the spring. Valent suggests applying Esteem in the fall when most leaves have dropped from the trees along with horticulture oil to clean up any hotspots of San Jose scale. It would still fall within the parameters of the label and count as a 2019 application. The suggested application is Esteem 5 ounces per acre plus horticultural mineral oil 1% v/v (summer or winter grade) in 200 gallons of water per acre with airblast or 400 gallons per acre with mist blower.

Variety sampling results

Many of the blocks we were sampling from are now harvested so there are only four cultivars in our sampling this week.

Apple maturity summary in Grand Rapids area for fruit harvested Oct. 15, 2019
Variety	Firmness lbs. (range)	Starch (range)	Brix% (range)
Northern Spy	17.8 (16-19.5)	4.1 (3-5)	14.4 (14-15)
Evercrisp	23.6 (20-26)	3.8 (2-8)	14.6 (14-16)
Fuji	18.2 (14-23)	5.6 (3-8)	14.9 (14-16)
Granny Smith	21 (18-24.5)	2.2 (1-4)	12.3 (12-13)

Individual Variety Results

Northern Spy

We added Northern Spy in our sampling this week per request. Sampling indicates Spy is ready for long-term controlled atmosphere (CA) storage, but not quite there for fresh sales—they do not eat very well yet even though brix is very good at 14.4.

Northern Spy 2019 maturity sampling records
Date of sample	Avg. Ethylene (ppm)	% Fruits with Ethylene over 0.2 ppm	Red color % (range)	Background color (range)	Avg Firmness lbs. pressure (range)	Starch (range)	Brix (range)
Oct. 15	77.8558	100	72 (60-100)	1.6 (1-2)	17.8 (16-19.5)	4.1 (3-5)	14.4 (14-15)

Evercrisp

Evercrisp is improving slowly in maturity parameters and very little has changed from last week’s sampling. Many growers use the starch-iodine test for apple maturity because it’s easy to do on your own. For Evercrisp, this might not be good to rely on alone as it just doesn’t stain very well, and you might think the starch clearing is higher than it really is. My colleagues seem to think using the background color is the best determination for maturity of Evercrisp—once that dark green color changes to lighter green, then it’s ready.

Evercrisp can be a high internal ethylene producer like its Honeycrisp parent, making this parameter ineffective as a maturity measurement as well. Of course, red color is important, so when red color is good and that greenish color lightens up, Evercrisp are ready.

Evercrisp 2019 maturity sampling records
Date of sample	Avg. Ethylene (ppm)	% Fruits with Ethylene over 0.2 ppm	Red color % (range)	Background color (range)	Avg Firmness lbs. pressure (range)	Starch (range)	Brix (range)
Oct. 8	0.4050	80	67.8 (40-90)	2.3 (1-3)	21.6 (19.5-24.2)	4.3 (2-7)	13.8 (12-16)
Oct. 15	0.4956	80	63 (30-100)	2	23.6 (20-26)	3.8 (2-8)	14.6 (14-16)

Fuji

Our predicted harvest date for late season Fuji is Oct. 28, which will be much too late for long-term CA storage. We are hearing that growers in the Grand Rapids area will start on Fuji at any time with next week being the main harvest window. Our sampling this week indicates the window for long-term CA storage is just opening and blocks with good red color can begin to be picked.

In years past when sugar levels are high as they seem to be this year, Fuji (and other varieties) can get callus tissue inside the core. This often is mistaken by buyers for moldy core. Just something to watch out for and if you see it and need my confirmation, please let me know by emailing me at irisha@msu.edu. Buyers have tried to reject loads for this non-defect. Check out the article “Moldy Core Of Apple” from Kari Peters at Penn State University Extension for a good comparison of moldy core and callus tissue with pictures to help with the identification.

Fuji 2019 maturity sampling records
Date of sample	Avg. Ethylene (ppm)	% Fruits with Ethylene over 0.2 ppm	Red color % (range)	Background color (range)	Avg Firmness lbs. pressure (range)	Starch (range)	Brix (range)
Oct. 1	0.6593	7	85 (50-100)	1.7 (1-2)	18.5 (15.3-25.5)	2.6 (1-6)	13.9 (12-16)
Oct. 8	1.1089	100	89 (80-100)	1.8 (1-2)	18 (15.5-20.5)	4.6 (3-7)	14.6 (14-16.5)
Oct. 15	0.3813	65	93 (60-100)	1.5 (1-2)	18.2 (14-23)	5.6 (3-8)	14.9 (14-16)

Granny Smith

Granny Smith is not a wide-planted variety, but it is one of the last to mature and interesting to watch. There has been very little forward movement in maturity from last week. This variety and other late varieties such as Pink Lady and Braeburn need at least two weeks to be even near early harvest.

Granny Smith 2019 maturity sampling records
Date of sample	Avg. Ethylene (ppm)	% Fruits with Ethylene over 0.2 ppm	Red color % (range)	Background color (range)	Avg Firmness lbs. pressure (range)	Starch (range)	Brix (range)
Oct. 8	0	0	3.9 (0-10)	4.3 (3-5)	18.7 (16.5-20.5)	2	11.3 (11-12)
Oct. 15	0.0476	0	1 (0-5)	3	21 (18-24.5)	2.2 (1-4)	12.3 (12-13)

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.
Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.

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