MSU Extension Apples

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.

Honeycrisp, Gala and McIntosh harvest is finished for many growers. Jonagold and Empire harvest has begun. Ambrosia is mature at some sites, and Golden Delicious are mature according to the starch rating. Rome, Mutsu, Idared and Red Delicious are still immature. Rome and Idared were only sampled at one location to get an idea of the maturity stage of those varieties; however, because they were more advanced than I thought they would be, I wanted to include them in the report. Testing at more sites will be completed next week.

For later maturing varieties, a product like aminoethoxyvinylglycine (AVG; ReTain) can be used, and applications at 28, 14 or seven days before harvest are recommended. For a 1-MCP product (Harvista), applications are recommended closer to harvest at seven or three days.

Weather over the past week was hot for this time of year with low temperatures in the mid- and upper 50s and low 60s and highs in the 70s and 80s across the region, according to the Hart Enviroweather station. A storm system over the weekend brought rain and slightly cooler weather. A total of 1.67 inches of rain has fallen since Sept. 20, according to the Hart Enviroweather station. Daytime temperatures will remain steady over the next few days with highs in the 70s and lows in the 50s. Chances of rain are forecasted later this week.

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 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 2025 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.
• New starch charts for evaluating apple maturity in Michigan from Michigan State University
• 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

Jonagold

Jonagold fruit were sampled from three locations in Oceana County. Red color is similar to last week at 90%. Background color is yellow-green at 2.4. Fruit firmness declined markedly this week with an average of 15.9 pounds of pressure. Starch is an average of 5.8, and fruit are mature. Sugars are similar to last week and are excellent at 13.8 Brix. Average diameter for sampled fruit was slightly larger than last week at 3.2 inches.

Empire

Fruit were sampled at one location in Oceana County. Harvest of Empire occurred already at some locations. Red color development is similar to last week, and background color is yellow green. Starch is clearing into the cortex with a rating of 4.7, and sugar levels are good at 12.1 Brix. Average fruit diameter was similar to last week at 2.6 inches. Empire are mature.

Ambrosia

Fruit were sampled at two locations in Oceana County. Red color development is at 68%, and fruit have a very nice blush. Background color is yellow, and firmness is 16.2 pounds of pressure. Starch has cleared significantly into the cortex compared to last week with an average rating of 5.5, and sugar levels are excellent at 14.5 Brix. Average fruit diameter was similar to last week at 2.9 inches.

Golden Delicious

Fruit were sampled at three locations in Oceana County this week. Red color development is at 42%, and there is a slight blush developing on the fruit surface. Background color is yellow green. Starch is clearing into the cortex with a rating of 4.5, and fruit are mature. Pressure is 16.2 pounds, and fruit could be harvested for mid- or long-term storage according to recommendations in the table below. Sugar levels are excellent at 14.7 Brix. Average fruit diameter is 2.8 inches.

Red Delicious

Fruit were sampled at two locations in Oceana County this week. Red color development is at 89%. Background color is yellow. Fruit firmness is an average of 17.7 pounds, and starch is clearing into the cortex with a rating of 2.3. Sugar levels are excellent at 13.2 Brix. Average fruit diameter is 2.9 inches.

Mutsu

Fruit were sampled at two locations in Oceana County this week. There is a slight blush on some fruit with 16% color, and background color is green. Fruit are very firm with pressure at 20 pounds. Starch is just starting to clear into the cortex with a rating of 1.7, and sugar levels are good at 12.6 Brix. Average fruit diameter is 3.1 inches.

Rome

Fruit were sampled at one location in Oceana County this week. Red color development is at 96.9%. Background color is green. Fruit are very firm with pressure at 25.2 pounds. Starch is clearing into the cortex with a rating of 2.8, and sugar levels are excellent at 13.3 Brix. Average fruit diameter is 2.8 inches.

Idared

Fruit were also sampled at one location in Oceana County this week. Red color development is at 69%. Background color is light green, and pressure is an average of 15.1 pounds. Starch is clearing into the cortex with a rating of 2.6, and sugar levels are good at 12.6 Brix. Average fruit diameter is 3.1 inches.

Apple maturity sampling parameters

• 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 For Honeycrisp: will typically be rated using the standard Michigan State University starch 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.