MSU Extension Apples

In the west central Michigan region, harvest of early apple varieties Zestar, Wildfire Gala and Premier Honeycrisp is wrapping up. Second pick of Minneiska is also occurring this week. Honeycrisp is now mature at some locations and could be harvested for medium-term storage. September Wonder Fuji and Brookfield and Pacific strains of Gala are almost mature and could be harvested for long-term storage shortly.

Weather

The weather over the past few days has been very hot with highs close to 90 degrees Fahrenheit and lows in the 60s and 70s. Following a severe thunderstorm on Tuesday, Aug. 27, temperatures have cooled gradually. This storm also brought 0.26 inches of rain according to the Hart Enviroweather station. For the rest of the week, high temperatures will be in the 70s, and low temperatures will be in the 50s and 60s across the region. Rain is also forecasted for Friday, Aug. 30. Over Labor Day weekend, high temperatures will be in the 70s with lows dipping down into the 40s. This will be excellent coloring weather.

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 six locations across Oceana County (Figure 1).

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 2024 from Michigan State University (MSU).
• More information on harvest management tools and timings.
• 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 MSU.
• 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

Honeycrisp

Fruit were sampled from six locations on Aug. 28 in Oceana County. Red color is 76%. Red color and size will continue to improve over the next few days following cooler daytime temperatures and cool nights in the 40s through the weekend and into next week. Background color is yellow green, and fruit are still mature at some sites. Pressure decreased to an average of 16.2 lbs., and starch rating averaged 4.1. Sugars are at 12 degrees Brix, but firmness, starch staining and Brix were variable from site to site. This variation was likely due to county location, planting age and crop load, and highlights the need to test fruit by block to best determine when to harvest fruit and how it should be stored to maintain quality. Harvest may need to be delayed for color development although pressure and starch should be carefully monitored for this variety.

Other things to note are that bitter pit has been observed in fruit on trees throughout the region (Figure 2). In addition, some fruit damage has been reported that appears to be from excessive sun or heat damage, likely from the heat wave in July. This damage caused sunken regions in sun-exposed surfaces of fruit and internal discoloration underneath the damaged area.

RubyMac

Fruit were harvested from two locations in Oceana County. RubyMac is a red coloring strain of McIntosh and is at a similar stage of maturity to standard strains of McIntosh in the area. Fruit are dark red. Background color and red color are similar to last week. Average firmness continues to decrease as was 14.1 lbs. Recommended pressure for short-term controlled atmosphere (CA) is 14 lbs. Fruit is close to mature with a starch rating of 3.5. McIntosh are mature at a starch test of 5. Sugar levels are fair at this stage with Brix at 11.4, similar to last week.

Gala

Gala fruit were sampled from six locations in Oceana County this week. Samples in the table below are for Brookfield and Pacific Gala. Red color is similar to last week, and background color is yellow. Fruit firmness was similar to last week with an average of 18.4 lbs. of pressure. The pressure range varied across sites. Starch cleared more this week and fruit are close to mature. Sugars are an average of 10.6 Brix. Fruit is almost ready to harvest for long-term CA storage.

September Wonder Fuji

Fruit were sampled at three locations in Oceana County this week. Fruit are still immature. Red color development is improving at 66% compared to last week. Background color is yellow green. Starch is similar to last week, and sugars are improving slightly at 10.8 Brix. Fruit size seems to be small this season.

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.