Grand Rapids area apple maturity report – September 13, 2023
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EmailThis is the first Grand Rapids area apple maturity report for the 2023 harvest season
This is the first Grand Rapids, Michigan, area apple maturity report for the 2023 harvest season. Reports are sent out every week (usually on Wednesdays), following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning.
- More information on harvest management tools and timings can be found in this article.
- Guidelines from MSU 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
How to read the maturity tables
Each week, we test apple varieties that are nearing maturity in the Grand Rapids region. We are reporting average values for several samples for each variety.
Updates for this week
Weather
The average temperature has been steadily decreasing this week with an average temperature of 80 degrees Fahrenheit on Sept. 5, declining to 58.5 F on Sept. 12. This has been great weather for red color development given that ideal temperatures for red color development are highs in the upper 70s F and lows in the upper 50s F. Additionally, cool night temperatures decrease respiration and the breakdown of sugars. Therefore, more sugars can remain in fruit and can be used to produce anthocyanins, which are responsible for red color development.
As of Sept. 12, the Michigan State University Enviroweather station for Sparta has reported an accumulation of 3,520.7 growing degree days (GDD) base 42 and 2,341.7 GDD base 50. We have had three rain events this week with a total weekly rainfall of 1.27 inches at the Sparta Enviroweather station.
Variety reports
Ambrosia
This variety was sampled at one location in Kent County this week. The starch is beginning to clear, and firmness is still quite high. This fruit is still immature.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
9/12/23 |
118.5 |
62.45 |
48 |
26.82 |
1.2 |
9.54 |
Fuji
This variety was sampled at one location in Kent County this week. Starch is clearing with an average of 3.4. Soluble sugars are low. The fruit is still very firm.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
9/12/23 |
157.3 |
74.1 |
52.5 |
20.93 |
3.4 |
8.17 |
Gala
This variety was sampled at three locations in Kent County. Gala is now being harvested and maturity parameters are in line with the guidelines listed below. However, fruit are still fairly firm.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
9/12/23 |
152.1 |
68 |
76.3 |
19.44 |
6.35 |
9.3 |
Gala with ReTain
Two locations with ReTain applications were sampled in Kent County. These samples had lower red color, higher firmness and lower starch rating compared to untreated Galas. Sugar levels were similar to Gala without ReTain.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
9/12/23 |
170.46 |
70.95 |
68.83 |
22.56 |
3.02 |
9.54 |
Honeycrisp
Honeycrisp was sampled in two orchards this week in Kent County. Across the state, sugar accumulation is lagging behind starch clearing for Honeycrisp. If color is well developed, Harvista applications may be appropriate at this point.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
9/12/23 |
182.7 |
74.1 |
74.75 |
17.9 |
7.4 |
10.15 |
Jonathan
This variety was sampled at one location this week in Kent County. Fruit firmness is high and sugar accumulation is low.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (Brix) |
|
9/12/23 |
64.58 |
64.58 |
95.5 |
21.05 |
4.4 |
8.61 |
McIntosh
This variety was sampled at one location this week in Kent County. Fruit firmness is high and sugar accumulation is low.
|
Collection Date |
Fruit Weight (g) |
Diameter (mm) |
Red Color (%) |
Firmness (lbs) |
Starch (1-8) |
Soluble Solids (°Brix) |
|
9/12/23 |
116.3 |
66.36 |
90.5 |
26.59 |
4.9 |
9.44 |
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.
- 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.
- Brix = % sugar measured with Atago PAL-1 Pocket Refractometer
Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.
|
Brix Guide |
Low |
Fair |
Good |
Excellent |
|---|---|---|---|---|
|
All varieties |
Less than 11 |
11 |
12 |
13 |
|
Honeycrisp |
Less than 12 |
12 |
12 |
Greater than 14 |
|
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 |
