MSU Extension Apples

Apple maturity testing will occur weekly for the Grand Rapids, 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 Grand Rapids, Michigan region, Golden Delicious, Red Delicious, Rome and Mutsu are being harvested this week. Some blocks of Idared and Aztec Fuji have also been harvested. Pink Lady and EverCrisp were also sampled this week, and samples from some sites were mature and ready for harvest.

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. 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.

With advancing maturity, applications of pre-harvest management tools may be needed to help maintain fruit quality and manage labor. 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, but a cool down finally came with a storm system on Oct. 6. Average temperatures over the past few days had low temperatures in the upper 30s and low 40s and highs in the 60s according to the Hart Enviroweather station. Daytime and nighttime temperatures will be similar over the next few days with highs in the 60s and lows in the 40s. This will be great coloring weather for later varieties such as Aztec Fuji, EverCrisp and Pink Lady.

The storm brought 0.72 inches of rain in Sparta, 0.54 inches in Belding and 0.85 inches in Grant according to local Enviroweather stations. Rain is also forecasted for 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 three locations in Kent County.

For more information about apple maturity testing, review these resources compiled by the MSU Extension tree fruit team.

• Predicted apple harvest dates for 2024 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 Grand Rapids region

Fuji

Fuji fruit, which includes Aztec Fuji, were sampled from four locations in Sparta. Fruit were treated with ReTain. Red color is an average of 73%, and background color is yellow green. Fruit firmness is at 18 pounds. of pressure. Starch is at 3.7, and sugars are excellent at 13.1 Brix. Average fruit diameter is 2.8 inches. Fruit are mature. For long-term storage, recommended pressure is 18 pounds, and the recommended starch rating is 3.

Red Delicious

Red Delicious fruit were sampled from three locations in Sparta. Red color is 93%, and background color is yellow-green. Fruit firmness is at 17.7 pounds of pressure. Starch is at 3.7, and sugars are excellent at 13.8 Brix. Fruit are mature. Average fruit diameter is 2.6 inches, similar to last week.

Idared

Idared were sampled from three locations in Sparta. Red color is an average of 81%, and background color is light green. Fruit firmness is at 15.5 pounds of pressure. Starch is at 3.3, and sugars are good at 12.4 Brix. Average fruit diameter is 3 inches. Fruit are almost mature. For long-term storage, recommended pressure is 16 pounds, and the recommended starch rating is 3.5.

EverCrisp

EverCrisp were sampled from four locations in Sparta and Grant. Red color is an average of 58%, and background color is green. Fruit firmness is at 22.1 pounds of pressure. Starch is at 3.3, and sugars are excellent at 15.1 Brix. Average fruit diameter is 3.1 inches. Fruit are almost mature.

Pink Lady

Pink Lady were sampled from one location in Grant. Pink blush is developing on the fruit with an average of 47% covering the fruit surface, and background color is yellow green. Fruit firmness is at 16.5 pounds of pressure. Starch rating is at 6.6. Some fruit are mature and ready for harvest, but this was highly variable across sites. Sugars are excellent at 14.4 Brix. Average fruit diameter is 2.5 inches.

Braeburn

Braeburn were sampled from one location in Sparta. Red color is an average of 71%, and background color is green. Fruit firmness is at 22.8 pounds of pressure. Starch is at 3, and sugars are good at 12.4 Brix. Average fruit diameter is 2.4 inches. Fruit are almost mature.

Granny Smith

Granny Smith were sampled from one location in Sparta. A slight blush is developing over the skin with an average of 11%, and background color is green. Fruit firmness is at 17.1 pounds of pressure. Starch is at 3.1, and sugars are fair at 10.1 Brix. Average fruit diameter is 3.2 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.