MSU Extension Apples

This is the seventh maturity apple maturity report for 2022. Reports are sent out every week (usually on Wednesdays), following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning. 

This week in the Grand Rapids area, harvest of Gala, Honeycrisp, and McIntosh is underway. 

***All sampled fruit are from untreated blocks (no ReTain or Harvista applied), unless otherwise indicated.*** 

Overall, fruit size is very large, crop load is excellent, and red color is developing very well. Fruit firmness is decreasing, and we noticed quite a few fruit that were softer than pressures recommended for long term storage in our samples this week. In addition, sugars continue to be a bit low across varieties. Most of this is likely a result of the ample rainfall this weekend and in previous weeks. Make sure to continue disease management all the way up to harvest. But don’t forget to pay attention to PHIs. A pre-harvest fungicide application is a very good way to control post-harvest and storage decay. A post-harvest fungicide fog treatment is also recommended to control decay in storage. This is especially true in varieties that are prone to decay such as Honeycrisp, McIntosh, and Jonagold. 

Weather conditions in the Grand Rapids area this week were warmer than normal and then finally started to feel more like fall. Temperatures were in the 80s Fahrenheit most of last week, but then dropped to the 60s F on Sunday and Monday following the front that moved through the area over the weekend. As of Sept. 12, the Michigan State University Sparta Enviroweather station has accumulated 3554.9 Degree Days Base 42 F (DD42). This is slightly above average, which is 3367.7 DD42, and approximately seven days ahead of normal.  

Significant rainfall occurred across the area on Sunday, ranging from 0.5 inches to over 1. inches of accumulation. At this time, most areas are not experiencing drought conditions, according to the US Drought Monitor.  

How to read maturity tables

Each week, we test apple varieties that are nearing maturity in the Grand Rapids. We are reporting average values for several samples for each variety. Maximum and minimum values are included for the highest and lowest individual fruits evaluated for each, to give a full spectrum of the maturity. All samples included in the reports have been untreated with ReTain or Harvista, unless otherwise noted.

• 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.

Gala (predicted harvest date: Sept. 7)

Samples collected this week included Pacific, Gale, and Brookfield strains. Fruit is mature this week in untreated blocks and in many blocks that have been treated. Size is excellent in most locations and continues to improve, following the rain this season. So far, we have observed very little shoulder cracking. Red color is dependent on strain, but in general is excellent this year. Background color changed significantly to light yellow this week. Fruit in all sample locations were producing ethylene this week: nearly 60% of fruit was producing significant amounts (greater than 0.2ppm) indicating maturity. Starch clearing was considerably more advanced this week. Most of our samples averaged 4-6 on the Cornell starch chart. Firmness is still good, with most samples averaging 17-20 lbs of pressure. Sugars improved a bit but are still a bit lower than ideal, possibly related to the abundant rainfall over the past few weeks.  

Recommended maturity indicators include pressures of 16-18, starch between 4-5, depending on anticipated length of storage. Color, size, and sugars depend greatly on market.

Honeycrisp (predicted harvest date: Sept. 15)

Honeycrisp first and some second pick is mature. Samples were all collected from ‘first pick’ fruit and should be used to guide early picking. We’ve seen a considerable amount of fruit pushing off trees, a result of the heavy crop load and very large fruit size, as well as short stems in many places. 

Red color development has improved significantly from last week. Background color is changing to light yellow in some places, but somewhat green in many places and second pick fruit; look for a change to pale yellow to indicate maturity. Starch clearing was advanced in first pick fruit this week with most fruit between 5-6. Note that this variety has an unusual starch staining pattern: it does not clear in the center first and then in the flesh like other varieties, but instead flesh may begin clearing first. WSU developed a separate scale for starch testing in Honeycrisp, using 1-6 scale. However, we are using a 1-8 scale like the SPI index developed for McIntosh, estimating the percentage of clearing. Sugars were between 10-12 °Brix in samples collected. Pressures were still good, ranging from 14-16 on average. We are noticing significant bitter pit in most locations, which is likely related to the rainfall and fruit size, possibly other conditions earlier in the season. 

Recommended maturity indicators include pressures between 15-17 lbs, starch between 4-5, depending on desired storage length. First pick is likely to begin next week in some locations, slightly ahead of our predicted harvest date. Some locations still need a bit more time. Spot picking only may be appropriate in some places.  

McIntosh (predicted harvest date: Sept. 12)

Untreated fruit of this variety is mature. Red color is developing well, although dependent on stain. Ethylene was present in significant amounts in 20% of fruit. Starch clearing was more advanced this week, with averages between 4-6, depending on block. Sugars were a bit better this week with averages between 10.5 and 11. Pressures decreased noticeably this week, averaging just over 14 in untreated fruit.  

Recommended maturity indicators are pressure between 14-16 lbs and starch pattern 3-5, depending on desired storage length and conditions. This variety is mature for shorter storage or direct market in most locations, very close to our predicted harvest date. 

Empire (predicted harvest date: Sept. 25)

Fruit is developing very nice color and size. Starch clearing is still just beginning and sugars are still a little lower than preferred. None of the fruit we tested were producing significant ethylene. Pressures were beginning to go down. This variety is nearly mature for storage, but needs a bit more time for shorter storage or direct market. 

Jonathan (predicted harvest date: Sept. 27)

This variety showed more signs of maturity this week. Red color is developing nicely, and background was a bit less green. A few of the fruit collected this week were producing a significant amount of ethylene (30%). Sugars improved just a bit, but are still lower than ideal. Fruit was considerably softer this week. Recommended pressures are 14-16 depending on the intended storage time. 

Jonagold (predicted harvest date: Sept. 27)

This variety is still immature but showing some signs of maturity. Samples collected this week were treated with ReTain—very few Jonagolds are untreated in the area this year. Red color development is still just beginning and background is still very green. Ethylene was not being produced in significant amounts in any fruit. Sugars are were a bit better, but still lower than ideal. Pressure was still very good in tested fruit; recommended pressure for this variety is 15-17, depending on the intended storage time.

Red Delicious (predicted harvest date: Oct. 1)

This variety is still immature. Red color is good in most locations, but background color is still very green. None of the fruit sampled this week were producing significant amounts of ethylene. Starch clearing is still just beginning. Sugars are still very low. Recommended pressures are 16-18 depending on the intended storage time. This variety is beginning to mature, but still needs a couple of weeks. 

Gold Delicious (predicted harvest date: Oct. 3)

This variety is still immature but beginning to show signs of maturity in some locations. Background color is still fairly green. Just a touch of pink is present on the blush side of a few fruit, but not most of the fruit on trees. Ethylene was being produced one of the fruit sampled this week, a poor indicator of the majority of the crop. Starch clearing is still just beginning. The pattern in this variety can also be a bit different than the traditional McIntosh starch staining, with flesh clearing before the entire core is clear. Recommended pressures for this variety are 15-17 depending on the intended storage time. Most fruit were well above this. Sugars are still a bit low as well. 

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.