Southwest Michigan apple maturity report – Sept. 12, 2018

William Shane<shane@msu.edu> - September 12, 2018

Gala and Honeycrisp harvest is underway in southwest Michigan.

Apple fruit with bitter rot symptoms, a fungal disease favored by hot wet conditions. Photo by B. Hubbard.

General apple harvest comments

The relatively warm conditions continues to push apple maturity quickly this year. The recent dry weather has generally cooperated with harvesting activity. Area growers are busy picking Gala and spot-picking Honeycrisp.

Please be aware that samples we collect for this report are from the central Berrien County region, targeting more mature fruit on the outside of the tree canopy. Fruit in the interior of the tree will be less advanced than shown here. Sites with heavier soils and greater crop loads will generally be less mature.

Brown marmorated stink bug is damaging fruit in some area orchards, especially orchard sides close to woods, soybean fields, ravines and where natural hosts such as buckthorn, tree of heaven and mulberry have served as food sources. Some gathering of stink bugs on sunny sides of buildings has begun, maybe triggered by cooler nights.

Oriental fruit moth, codling moth, obliquebanded leafroller, apple maggot and San Jose scale are additional pests of concern at this time of year. Sooty blotch and flyspeck diseases are favored by the warm, wet conditions we have had in recent days. A few apples, especially light colored varieties, are infected by the fungal disease bitter rot, which appears as circular, dark fruit spots with salmon-orange, slimy spores most visible under rainy conditions.

Apple maturity in southwest Michigan for apples harvested Sept. 11
Variety	Firmness lbs. (range)	Starch (range)	Brix %
Gala	20.0 (22.0-17.0)	5.4 (4.4-7.0)	12.6
Honeycrisp	15.9 (15.0-17.0)	5.3 (4.2-7.0)	12.3
Jonagold	19.5 (18.0-21.0)	2.3 (1.2-3.6)	11.4

Individual variety results

Gala was sampled for the third week. Last week, starch readings for the past two weeks jumped from 1.5 to 3.3, to 5.4 for this week, so apple maturation has proceeded rapidly. All seven Gala sites tested this week had starch conversion of 4.4 or greater, well in the mature zone. Target starch index for maturity for this variety is 3.

Although the area average firmness was 20 pounds for this week, two of seven sites had fruit firmness at or below the minimum firmness of 18 pounds recommended for long-term controlled atmosphere (CA) storage. Predicted peak harvest date for central Berrien County is Sept. 10.

Gala maturity sampling for the harvest season
Sample date	Firmness lbs. (range)	Starch (range)	Brix %
Aug. 28	25.4 ( 22.0-28.0)	1.5 (1.4-1.6)	11.8
Sept. 4	23.0 (21.3-25.0)	3.3 (1.8-4.6)	11.8
Sept. 11	20.0 (22.0-17.0)	5.4 (4.4-7.0)	12.6

Honeycrisp was sampled for the third week and is showing rapid maturation. Starch conversion moved from an average of 2.9 last week to 5.3 for this week, all sites testing above the target mature starch index of 3.5 for this variety. The predicted peak harvest date is Sept. 18 for central Berrien County, so this variety is maturing ahead of the predicted date.

Fruit firmness is averaging 15.9 pounds this week, almost 2 pounds less than last week, with the general guideline of 17 pounds for best long-term CA storage and 16 for mid-term storage.

Honeycrisp maturity sampling for the harvest season
Sample date	Firmness lbs. (range)	Starch (range)	Brix %
Aug. 28	20.0 (17.0-23.1)	1.8 (1.6-1.8)	12.0
Sept. 4	17.7 (16.2-19.0)	2.9 (1.6-4.8)	11.6
Sept. 11	15.9 (15.0-17.0)	5.3 (4.2-7.0)	12.3

Jonathan was not sampled because most area blocks have been picked for taffy apples.

Jonagold was sampled for the first time this season. Starch conversion is averaging 2.3 this week, with 3.5 as the target for mature for this variety. The predicted peak harvest date is Sept. 24 for central Berrien County, which seems to indicate this variety is maturing slightly ahead of prediction. Brix for this week is 11.4.

Fruit firmness averaged 19.5 pounds this week, with the general guideline of 17 pounds for best long-term CA storage. Watch this variety closely as both the firmness and internal starch conversion seems to be moving rapidly toward maturity.

Jonagold maturity sampling for the harvest season
Sample date	Firmness lbs. (range)	Starch (range)	Brix %
Sept. 11	19.5 (18.0-21.0)	2.3 (1.2-3.6)	11.4

Empire was sampled for the first time this season. Starch conversion is averaging 2.1 this week, with 3.5 as the target for mature for this variety. The predicted peak harvest date is Sept. 23 for central Berrien County. Brix for this week is 11.4.

Fruit firmness averaged 18.5 pounds this week, with the general guideline of 16 pounds for best long-term CA storage. Based on these tests, harvest for fresh market can be delayed to wait for better size and quality.

Empire maturity sampling for the harvest season
Sample date	Firmness lbs. (range)	Starch (range)	Brix %
Sept. 11	18.5 (18-20)	2.1 (1.8-2.6)	11.2

Golden Delicious was sampled for the first time this season. Starch conversion is averaging 1.5 this week, with 3 as the target for mature for this variety. The predicted peak harvest date is Sept. 27 for central Berrien County.

Brix for this week is 11.4. Fruit firmness averaged 18.2 pounds this week, with the general guideline of 17 pounds for best long-term CA storage. One site is already testing below the 17 pound threshold. As seems to be the case this year, watch this variety carefully as apples seem to be ripening before the predicted harvest date.

Golden Delicious maturity sampling for the harvest season
Sample date	Firmness lbs. (range)	Starch (range)	Brix %
Sept. 11	18.2 (16-20)	1.5 (1.0-2.4)	11.1

Early Fuji is testing well in the mature zone. Starch conversion is averaging 4.9 this week, with 3 as the target for mature for this variety. The predicted peak harvest date is Sept. 1 for central Berrien County.

Brix for this week is 13.3. Fruit firmness averaged 17 pounds this week, with the general guideline of 18 pounds for best long-term CA storage, although this variety is generally used for direct fresh sales rather than long term storage.

Early Fuji maturity sampling for the harvest season
Sample date	Firmness lbs. (range)	Starch (range)	Brix %
Sept. 11	17.0 (16-18)	4.9 (4.0-6.2)	13.3

For additional comments from Randy Beaudry, MSU Department of Horticulture, read his general observations from MSU Apple Maturity Lab for 2018.

Normal and predicted 2018 peak harvest dates for apple varieties in southwest Michigan based on weather data at the Southwest Michigan Research and Extension Center, Benton Harbor, MI.
Variety	Normal date	2018 Predicted peak harvest date
Paula Red	Aug. 22	Aug. 20
Zestar	Aug. 22	Aug. 20
Gingergold	Aug. 20	Aug 18
McIntosh	Sept. 10	Sept 8
Gala	Sept. 8	Sept 6.
Early Fuji	Sept. 3	Sept. 1
Honeycrisp	Sept. 13	Sept. 13
Empire	Sept. 19	Sept. 23
Jonathan	Sept. 22	Sept. 24
Jonagold	Sept. 22	Sept. 24
Golden Delicious	Sept. 25	Sept. 27
Red Delicious	Sept. 28	Oct. 1
Ida Red	Oct. 5	Oct. 8
Rome	Oct. 5	Oct. 8
Fuji	Oct. 20	Oct. 22
Braeburn	Oct. 20	Oct. 22
Goldrush	Oct. 26	Oct. 28

Suggested firmness and starch index levels for long-term and shorter-term controlled atmosphere (CA) storage by variety.
Variety	Firmness (pounds)*			Starch Index*
Variety	Short CA	Mid-CA	Long CA	Mature	Over mature
McIntosh	14	15	16	5	7
Gala	16	17	18	3	6
Honeycrisp	15	16	17	3.5	7
Empire	14	15	16	3.5	6
Early Fuji	16	17	18	3	7
Jonagold	15	16	17	3.5	5.5
Jonathan	14	15	16	3.5	5.5
Golden Delicious	15	16	17	3	6.5
Red Delicious	16	17	18	2.5	6
Idared	14	15	16	3.5	6
Fuji	16	17	18	3	7
Rome	15	16	18	3	5.5

*Firmness is measured with a mechanical 11-millimeter wide probe inserted into the pared flesh of a fruit to a distance of 8 millimeters. Starch index is measured on equatorial cross section of an apple stained with iodine solution and rated using the Cornell University starch-iodine index chart for apples on a 1-8 scale (Predicting Harvest Date Window for Apples by Blanpied and Silsbey, Cornell Extension Bulletin 221.)

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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