MSU Extension Apples

Apple maturity testing will occur weekly for the west central region beginning now through the end of apple harvest. Reports will be sent out every week, following the Wednesday morning Michigan State University Extension fruit team apple maturity calls.

In the west central region, growers are harvesting Gala and Honeycrisp this week. Some growers have also harvested September Wonder Fuji. Jonagold and Empire are showing signs of maturing this week. Golden Delicious and Red Delicious are still immature. Overall, apple harvest is moving steadily, crop load is excellent, and red color continues to develop well.

Weather over the past week has generally been cool with rain showers. Daytime temperatures have ranged from the 50s and 60s, and nighttime temperatures have ranged from the 30s to 50s. As of Sept. 28, the Enviroweather station for Hart has reported an accumulation of 3632 DD₄₂ and 2378 DD₅₀.

Storms brought steady rain across the region this week. Slightly warmer temperatures are forecasted for the remainder of the week with highs 60s and 70s. Cooler night temperatures are also forecasted this week, and low temperatures on Wednesday – Thursday may be close to freezing.

With regular rain events, growers should maintain fungicide coverage to minimize late season rots, particularly for fruit that will be in long-term storage. Rainfall over 2 inches can wash off fungicide residues on fruit. Excessive rain may also have an impact on fruit by temporarily diluting flavor and brix (sugars).

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 two to three locations across Oceana County.

For more information about apple maturity testing, review these resources compiled by Anna Wallis and Amy Irish Brown, MSU Extension.

• Predicted apple harvest dates for 2022 from MSU
• 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
• Starch chart for Honeycrisp Apples developed by Washington State University.

Maturity information for the west central region

Empire

Fruit were sampled from three locations on Sept. 26 in Oceana County. Red color development is good with an average of 69.5%. Background color is still quite green but is improving. Average fruit firmness is at 16.4 but varied across locations. Starch clearing is still light. Sugar levels are improving and are considered fair according to the Brix table below. This variety still needs a little more time before it is mature for long-term storage.

Jonagold

Fruit were sampled from three locations on Sept. 26 in Oceana County. Red color development is good, and background color is light green. Fruit firmness varied from site to site with an average of 15.1. Pressure was still good in tested fruit. Recommended pressure for this variety is 15-17, depending on the intended storage time. On average, more starch is being converted to sugar, and the starch rating is 4.2. Sugars levels are excellent at 13.0 according to the Brix table below. Some fruit at one location also had mild water core.

Golden Delicious

Fruit were sampled from three locations on Sept. 26 in Oceana County. Background color is transitioning from light green to more yellow. Some fruit are also showing a light blush with a touch of pink. Fruit firmness varied from site to site with an average of 15.5. On average, starch clearing is 3.4, and sugars levels are excellent at 13.9 according to the Brix table below.

Red Delicious

Fruit were sampled from two locations on Sept. 26 in Oceana County. Red color development is very good with most fruit being fully red. Fruit firmness varied from site to site with an average of 16.0. On average, starch clearing is low, and sugars levels are still low according to the Brix table below. This variety is still immature.

Mutsu

Fruit were sampled from two locations on Sept. 26 in Oceana County. This variety is still immature. Background color is light green, and some fruit have a light pink blush. Fruit firmness varied from site to site with an average of 17.0. On average, starch clearing is low, and sugars levels are good according to the Brix table below.

Idared

Fruit were sampled from three locations on Sept. 26 in Oceana County. Red color development is at 67.5% on average, and background color is light green at a rating of 3.1. Fruit firmness varied from site to site with an average of 17.0. On average, starch clearing is low, and sugars levels are fair according to the Brix table below. This variety is still immature.

Rome

Fruit were sampled from two locations on Sept. 26 in Oceana County. Red color development is very good with most fruit being fully red. Fruit firmness varied from site to site with an average of 20.9. On average, starch clearing is low, and sugars levels are still low according to the Brix table below. This variety is still immature.

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 Maturity page for regional reports throughout the state and additional resources.