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 MSU Fruit Team apple maturity calls. 

In the West Central region, growers are finishing harvest of early varieties such as Minneiska and Premier Honeycrisp. For Gala, some early strains, such as Pacific and Brookfield, may be ready for long-term storage. McIntosh, Honeycrisp, and September Wonder Fuji are showing signs of maturity development but are still immature. 

Weather over the past week has generally been warm and dry. Daytime temperatures have ranged from the low 70s to low 80s Fahrenheit, and nighttime temperatures have been in the 50s and 60s F. Ideal temperatures for red color development are highs in the upper 70s F and lows in the upper 50s F. Bright and sunny conditions enhance photosynthesis and sugar accumulation. Cool night temperatures decrease respiration and the breakdown of sugars. Therefore, more sugars can remain in fruit and can be used to produce anthocyanins which are responsible for red color development. 

As of Sep. 7, the Enviroweather station for Hart has reported an accumulation of 3236.4 DD42 and 2135.5 DD50. Scattered rainfall occurred on Saturday, Sep. 3 across the region. The Hart Enviroweather station reported a total of 0.15 inches of rainfall, and the Fremont weather station report a total of 0.76 inches of rain. No rainfall was reported for the Ludington weather station. 

The long-range weather forecast is generally predicted to be warmer and drier than normal. Rain is predicted across the region for Sep. 11 and 12. Rainfall over 2 inches can wash off fungicide residues on fruit. Growers should maintain fungicide coverage to minimize late season rots, particularly for fruit that will be in long-term storage. 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 four 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 

Gala

Early samples of Brookfield Gala and Pacific Gala were collected at five locations on Sep. 6 and 7 in Oceana County. Generally, fruit is at a stage where it could be picked for long-term CA storage according to Gala recommendations in the table below. Fruit size is improving, especially in blocks with a moderate crop load. Red color is also improving, and some blocks are highly colored depending on the Gala strain. Background color is improving and becoming more yellow with a creamy color. Firmness is decreasing with an average of 17.4 lbs. Sugars are increasing, and fruit starch was variable from site to site with some fruit staining at 1 (no starch conversion detected) and other fruit staining at 8 (majority of starch converted). 

September Wonder Fuji 

Fruit were sampled at three locations on Sep. 7 in Oceana County this week. Fruit are generally immature, but some locations had more advanced maturity than others. Red color development is moderate, and background color is turning to lighter green. Starch is beginning to clear at some locations, and sugars levels increased from last week.  

Honey Crisp

Fruit were sampled from three locations on Sep. 6 and 7 in Oceana County. Fruit continue to size with some fruit being quite large. Red color development is also increasing to an average of 67.5% red color. Background color is changing slightly to lighter green. Fruit firmness is also decreasing slightly, and starch is clearing to an average of 5. Sugar levels are increasing and are considered good according to the Brix table below. 

Bitter pit has been observed in some locations. Fruit that are high risk or are more susceptible to bitter pit development may be in blocks with younger trees, high-risk rootstocks, or high-vigor trees. Large fruit are also more susceptible to bitter pit development than small fruit. High bitter pit-risk fruit should be cooled quickly to the recommended 38 F storage temperature, as conditioning will exacerbate bitter pit. High risk fruit should be marketed as soon as possible. Fruit intended for longer-term storage should be pre-conditioned, with recommended conditions of 68 F (room temperature) for five to seven days. 

McIntosh 

Fruit were sampled from three locations on Sep. 6 and 7 in Oceana County. Red color development is increasing, and background color is still quite green. Fruit firmness is also decreasing slightly. On average, starch clearing is moderate, and sugars levels are still considered low according to the Brix table below.  

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.