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 MSU Fruit Team apple maturity calls on Wednesday mornings. 

In the West Central region, early varieties being harvested this week include Premier Honeycrisp and Minneiska. Other early varieties, such as Gingergold and Zestar, have now been harvested. September Wonder Fuji and early strains of Gala continue to show some signs of maturity. McIntosh and Honeycrisp are also starting to show early signs of maturity development but are still immature. 

Weather over the past week has been warm and dry. Daytime temperatures have ranged from the low 70s to low 80s, and nighttime temperatures have been in the 50s and 60s. As of Sep. 1, the Enviroweather station for Hart has accumulated 3378.9 DD42 and 2037.2 DD50. Rainfall occurred on Aug. 28 and 29, and some areas accumulated over 2 inches of rain. 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. The rain may also have an impact on fruit by temporarily diluting flavor and brix (sugars). 

Expect warm and dry conditions on Friday. Light rainfall is predicted for this weekend across the region. Medium range forecasts indicate slightly warmer and wetter conditions than normal. 

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 

Ginger Gold  

Ginger Gold was sampled in one location in Oceana County this week. This variety is mature, and growers finished picking fruit this week. The main maturity index for Ginger Gold is color. Background color has changed from an average of 4.7 last week to 2.1 this week and is a pale yellow or cream (1 or 2 on the background color scale). Some fruit has developed a pink blush on the sun-side of fruit. Fruit have softened from an average of 17.9 lbs pressure (firmness) last week to 13.8 lbs pressure this week. Sugars are at a fair level, and starch cleared rapidly from last week.

Gala

Early samples of Brookfield Gala and Pacific Gala were collected at four locations on Aug. 29 in Oceana County. Fruit is still mostly immature. Size is improving, especially in blocks with a moderate crop load. Red color is variable but generally improving. Background color is also improving and becoming more yellow in some locations. Fruit are generally firm, but firmness varied by location. Sugars are still low, and fruit starch is beginning to clear.  

September Wonder Fuji 

Fruit were sampled at four locations 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 are increasing.  

Minneiska

Fruit were sampled at three locations on Aug. 29 and Aug. 30 in Oceana County. Minneiska (SweeTango) is an early apple with bright color. Fruit are mature, and growers have started picking this week. Red color development continues to increase, and background color is also changing from yellow to a cream color. Starch is clearing at some locations, and sugars are fair. Sugar levels decreased from last week in our samples which may be due to rainfall in the area. 

Honey Crisp

Fruit were sampled from three locations on Aug. 29 and Aug. 30 in Oceana County. Fruit are still immature and are quite firm. Average red color is 59% and background color is still green with an average of 4. Sugar levels are fair. 

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 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 Aug. 29 and 30 in Oceana County. Fruit are still immature. Red color development was moderate, and background color is still quite green. On average, starch clearing and sugars levels are still low.  

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.