West central Michigan apple maturity report – October 4, 2023
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EmailGolden Delicious and early strains of Red Delicious are being harvested this week while some growers have also started picking Idared and Rome for long-term storage.
Apple maturity testing will occur weekly for the west central Michigan region beginning now through the end of harvest. Reports will be sent out every week following the Michigan State University Extension fruit team apple maturity calls on Wednesday mornings.
In the west central region, growers are beginning to harvest Golden Delicious and Rome. Red Delicious are now mature according to the starch index chart below and could be harvested for long-term storage. Idared and Rome starch rating is close to 3, and fruit are still very firm. Apples around the state are maturing more rapidly than expected. Growers may need to apply Harvista and ReTain to help slow down maturity and manage available labor.
Weather update
Weather over the past week has been unseasonably warm. A cooldown is expected going into the weekend. Sugar levels continue to be good or excellent depending on the variety. There is a high level of variability in fruit maturity within trees and across blocks this season. Testing fruit maturity for individual blocks is important this year to identify best harvest timing.
As of Oct. 3, the Enviroweather station for Hart has reported an accumulation of 3,760 growing degree days (GDD) base 42 and 2,462 GDD base 50. Temperatures will cool down over the next few weeks highs in the 50s and 60s degrees Fahrenheit and lows in the 40s F.
How to read maturity tables
Each week, an apple maturity report will be provided and will include average values for several apple samples for varieties nearing maturity. Maximum and minimum values are included in tables below for the highest and lowest individual fruits evaluated for each, to give a full spectrum of maturity. All samples included in the reports have been untreated with ReTain or Harvista, unless otherwise noted. Samples were collected from three to five locations across Oceana County.
For more information about apple maturity testing, review these resources compiled by the MSU Extension tree fruit team.
- Predicted apple harvest dates for 2023 from MSU Extension.
- More information on harvest management tools and timings can be found in this article.
- Guidelines from MSU Extension to check for apple maturity in your own orchard, including specific pressure and starch recommendations by variety.
- Predicting apple maturity and starch chart from Cornell University.
- Starch chart for Honeycrisp apples developed by Washington State University.
Maturity information for the west central region
Golden Delicious
Fruit were sampled from three locations on Oct. 2 in Oceana County. Fruit are yellow green with a light blush. Fruit firmness is decreasing with an average of 16.2 lbs. Starch is clearing with a rating of 6.3, and sugars levels are excellent. Fruit are ready for harvest.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 18 |
125 (138-109) |
21 (40-5) |
4.2 (5-3) |
19.0 (21.6-16.2) |
3.5 (6-1) |
13.6 (14.3-13.2) |
|
Sept. 25 |
128 (162-106) |
27 (45-0) |
3.8 (4-1) |
17.4 (19.6-14.4) |
5.7 (7-3) |
14.2 (14.7-13.5) |
|
Oct. 3 |
132 (143-119) |
38 (50-0) |
3.2 (4-1) |
16.2 (20.7-14.4) |
6.3 (8-4) |
14.7 (15.2-14.3) |
Red Delicious
Fruit were sampled at three locations on Oct. 2 in Oceana County. Firmness is decreasing and is at 16.7 lbs. Starch is clearing in the flesh. Sugar levels have improved and are at 12.5 Brix. Fruit are mature and are ready for harvest.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 18 |
148 (156-138) |
92 (100-70) |
3.3 (4-3) |
18.0 (19.6-16.0) |
1.9 (3-1) |
10.6 (11.1-10.1) |
|
Sept. 25 |
148 (168-120) |
98 (100-80) |
1.5 (3-1) |
17.4 (19.4-15.8) |
2.9 (5-1) |
12.1 (13.4-10.4) |
|
Oct. 3 |
163 (169-158) |
93 (100-70) |
1.2 (3-1) |
16.7 (18.1-14.9) |
3.1 (8-2) |
12.5 (13.6-11.3) |
Idared
Idared samples were collected at three locations on Oct. 2 in Oceana County. Fruit weight is similar to last week at 187 g, and red color is 79%. Background color is yellow green. Fruit firmness decreased to 15.4 lbs. Starch rating and sugar are similar to last week. Fruit are still immature according to the starch index below.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 25 |
186 (212-166) |
69 (98-40) |
3.6 (5-2) |
17.7 (19.3-16.4) |
2.9 (4-1) |
12.4 (12.9-12.0) |
|
Oct. 3 |
187 (204-153) |
79 (99-45) |
2.8 (4-1) |
15.4 (16.9-13.4) |
3.1 (5-2) |
12.1 (12.6-11.6) |
Rome
Fruit were sampled from two locations on Oct. 2 in Oceana County. Red color development is at 99%. Background color is yellow, and fruit are very firm with an average firmness of 21.2 lbs. Starch and sugar levels are similar to last week. Sugar levels are good according to the Brix table below. Fruit are mature according to the starch chart, but are still quite firm. Recommended fruit firmness for long-term controlled atmosphere (CA) storage is 18.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Sept. 25 |
153 (186-121) |
95 (100-70) |
2.4 (4-0) |
23.1 (26.3-20.3) |
3.1 (4-3) |
12.6 (13.3-11.9) |
|
Oct. 3 |
175 (202-148) |
99 (100-95) |
1 (1-1) |
21.2 (25.3-18.8) |
3.1 (4-3) |
12.2 (13.2-11.2) |
Crispin
Fruit were sampled from two locations on Oct. 2 in Oceana County. Background color is green, and fruit have a slight blush. Fruit are firm with an average firmness of 18.7 lbs. Starch rating is 3.7. Sugar levels are good according to the Brix table below. Some blister rot was observed at a few orchard sites. Some watercore was observed in this variety.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Oct. 3 |
239 (261-210) |
21 (50-0) |
4.1 (5-2) |
18.7 (22.4-15.5) |
3.7 (7-1) |
12.6 (13.8-10.5) |
Aztec Fuji
Fruit were sampled from two locations on Oct. 2 in Oceana County. Red color development is at 83%. Background color is light green, and average fruit firmness is 16.4 lbs. Starch clearing is 4.1, and sugar levels are excellent according to the Brix table below. Fruit are mature according to the starch chart and could be harvested for controlled atmosphere (CA) storage.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Oct. 3 |
203 (234-172) |
83 (99-50) |
3.7 (4-2) |
16.4 (18.7-14.6) |
4.1 (6-3) |
13.2 (13.3-13.1) |
EverCrisp
Fruit were sampled from three locations on Oct. 2 in Oceana County. Red color development is at 65%. Background color is green, and fruit are firm with an average firmness of 21.4 lbs. Starch clearing is higher than expected at this stage, and the starch average rating is 3.6. Sugar levels are excellent according to the Brix table below. Some watercore was observed in this variety.
|
Collection Date |
Fruit Weight (g) |
Red Color (%) |
Background color (5-1) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
Oct. 3 |
238 (273-193) |
65 (95-50) |
4 (5-3) |
21.4 (25.2-19.3) |
3.6 (6-1) |
15.7 (16.8-14.2) |
Apple maturity sampling parameters
- Ethylene (% 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. Indicates surface area covered in red and intensity of red color.
- Background color: 5 = Green, 1 = Yellow; range is of all fruits tested.
- Firmness in pounds pressure = measured with a Güss Fruit Texture Analyzer; 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.
- Starch for Honeycrisp: will typically be rated using the standard Cornell SPI scale (1-8). However, a separate starch chart for Honeycrisp apples developed by Washington State University (scale 1-6) also exists.
- Brix = % sugar measured with Atago PAL-1 Pocket Refractometer.
Looking for more? View Michigan State University Extension’s Apple page for regional reports throughout the state and additional resources.
|
Suggested firmness and starch index levels for long-term and shorter-term controlled atmosphere (CA) storage by variety. |
|||||
|---|---|---|---|---|---|
|
Variety |
Firmness (pounds)* |
Starch Index* |
|||
|
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 |
6 |
|
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 |
|
Brix Guide |
Low |
Fair |
Good |
Excellent |
|---|---|---|---|---|
|
All varieties |
Less than 11 |
11 |
12 |
13 |
|
Honeycrisp |
Less than 12 |
12 |
12 |
Greater than 14 |