MSU Extension Apples

In the west central Michigan region, Jonagold and Empire harvest is wrapping up. Harvest began for Ambrosia, and Golden Delicious harvest will be coming shortly. Rome, Mutsu, Idared and Red Delicious are close to maturity. Only one sample of Aztec Fuji was sampled this week, but it was mature according to the starch chart. While it is early for this variety to be mature, check individual blocks to determine if harvest is needed. Pink Lady and EverCrisp were also sampled this week for initial testing. These varieties showed early signs of maturity, and they will continue to be monitored over the next few weeks.

Maturity dates are tracking more closely to last year with varieties being harvested about two weeks ahead of normal. High heat in August and September seems to have significantly advanced growing degree days and maturity later in the season. Be sure to monitor your blocks to harvest at the optimal maturity stage for each variety and target storage conditions. Communicate this information to packers and processors to facilitate proper storage and optimize fruit quality.

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. Average temperatures were above normal with low temperatures in the upper 40s and mid-50s and highs in the upper 70s and low 80s across the region, according to the Hart Enviroweather station. Daytime and nighttime temperatures will be similar over the next few days with highs in the 70s and lows in the 50s. Conditions are forecasted to be dry for the rest of the 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 Michigan State University 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

Ambrosia

Fruit were sampled at two locations in Oceana County. Red color development is at 70%, and fruit have a very nice blush. Background color is yellow, and firmness is similar to last week at 17.3 pounds of pressure. Starch has cleared into the cortex, and sugar levels are still excellent at 14.3 Brix. Average fruit diameter was similar to last week at 2.9 inches.

Golden Delicious

Fruit were sampled at three locations in Oceana County. There is a slight blush developing on the fruit surface with coverage of 22% of the fruit surface. Background color is yellow green. Starch is clearing into the cortex with a rating of 5.4, and fruit are mature. Pressure is 17.1 pounds, and fruit could be harvested for mid- or long-term storage according to recommendations in the following table. Sugar levels are excellent at 15.2 Brix. Average fruit diameter is 2.9 inches.

Red Delicious

Fruit were sampled at three locations in Oceana County. Red color development is at 91%. Background color is yellow. Fruit firmness is an average of 17.1 pounds, and starch rating is similar to last week at 2.4. Sugar levels are excellent at 13.7 Brix. Average fruit diameter is 2.8 inches.

Mutsu

Fruit were sampled at three locations in Oceana County. There is a slight blush on some fruit with 10% color, and background color is light green. Fruit are very firm with pressure at 19.8 pounds. Starch is just starting to clear into the cortex with a rating of 1.8, and sugar levels are good at 12.3 Brix. Average fruit diameter is 3.4 inches. Fruit maturity is similar to last week.

Rome

Fruit were sampled at two locations in Oceana County. Red color development is at 97%. Background color is yellow green. Fruit are very firm with pressure at 23.3 pounds. Starch is similar to last week with clearing into the cortex and a rating of 2.7. Sugar levels are good at 12.3 Brix. Average fruit diameter is 3 inches.

*Values from Sept. 22 were only from one location.

Idared

Fruit were sampled from five locations in Oceana County. Red color development is at 73%. Background color is light green, and pressure is an average of 16.3 pounds. Starch is clearing into the cortex with a rating of 2.1, and sugar levels are good at 12.1 Brix. Average fruit diameter is 3.1 inches. There was some watercore observed for this variety.

*Values from Sept. 22 were only from one location.

Aztec Fuji

Fruit were sampled from one location in Oceana County. Red color development is at 65%. Background color is yellow green, and pressure is an average of 16 pounds. Starch is clearing into the cortex with a rating of 3.8, and sugar levels are good at fair at 11.4 Brix. Average fruit diameter is 2.9 inches. There was some watercore observed for this variety. While this is only one site, fruit are considered mature and could be harvested for storage. This is much earlier than expected and is head of the predicted harvest date for Fuji. This is a good reminder to monitor individual blocks and evaluate their maturity at your site.

*Values from Sept. 22 were only from one location.

Northern spy

Fruit were sampled from two locations in Oceana County. Red color development is at 73%. Background color is yellow green, and pressure is an average of 20.6 pounds. Starch is clearing into the cortex with a rating of 3.5, and fruit are mature. Sugar levels are good at 12.5 Brix. Average fruit diameter is 3.5 inches.

Pink Lady

Fruit were sampled from two locations in Oceana County. A nice blush is starting to develop on the fruit and covering 65% of the fruit surface. Background color is light green, and pressure is an average of 18.5 pounds. Starch is clearing into the cortex with a rating of 3.3, and sugar levels are good at 12.5 Brix. Average fruit diameter is 2.7 inches.

EverCrisp

Fruit were sampled from three locations in Oceana County. Red color development is at 71%. Background color is green, and pressure is an average of 20 pounds. Starch is starting to clear into the cortex with a rating of 2.2, and sugar levels are excellent at 13.1 Brix. Average fruit diameter is 3 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.