MSU Extension Apples

This is the sixth apple maturity report for 2022. Reports are sent out every week (usually on Wednesdays), following the MSU Fruit Team apple maturity calls on Wednesday morning. 

This week in the Grand Rapids area, harvest of Gala, Honeycrisp, and McIntosh is beginning. In general, fruit maturity is moving slowly, allowing plenty of time for adequate color and quality, and time to manage harvest. 

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

Weather conditions in the Grand Rapids area this week were slightly warmer than normal. Temperatures were in the upper 70s to 80 Fahrenheit most of the week, with overnight lows in the upper 50s to 60 F. This was followed by a significantly cooler trend Sunday through Tuesday, with mostly overcast skies and highs in the 70s F. As of Sep.5, the Michigan State University Sparta Enviroweather station has accumulated 3385.1 Degree Days Base 42°F (DD42). This is slightly above average, which is 3231.2 DD42, and approximately seven days ahead of normal.  

Some rainfall occurred over the weekend, but accumulation was variable. There was little rainfall recorded by weather stations in the Sparta area, while Clarksville and Belding Enviroweather stations recorded less than one inch. At this time, most areas are not experiencing drought conditions, according to the US Drought Monitor.  

The weather system hovering over our region since before the weekend will slowly move east throughout Tuesday and Wednesday. This will be followed by a high-pressure system over our region, including warmer, fair conditions for the remainder of the week, with highs in the 80s F. The next chance of precipitation will be Saturday evening and Sunday, with likely accumulation of 0.5 inch of rain. This will be followed by cooler, more fall-like conditions, with highs in the 70s F and overnight lows in the 40s-50s F. Both medium and longer-range forecasts indicate slightly warmer, drier conditions than normal over the next two weeks, and the remainder of the season.

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: Sep. 7)

Samples collected this week included Pacific, Gale, and Brookfield strains. Fruit is maturing gradually. Size is excellent in most locations and continues to improve. Red color is dependent on strain, but in general is excellent this year. Background color is beginning to fade from green to pale green and light yellow this week. More fruit were producing ethylene this week: in half of our samples 40% of fruit was producing significant amounts (>0.2ppm) indicating most locations are on the cusp of maturity. Starch clearing is moving slowly. Most of our samples averaged 2-3 on the Cornell starch chart, while a few earlier sites had a few fruit that were further along. Overall, fruit is still very firm, and samples averaged 18-20 lbs of pressure, with a few softer fruit again bringing down our average. Sugars are still a bit lower than ideal, possibly related to the abundant rainfall over the past few weeks but expected to catch up in time for harvest.  

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 the market. Harvest of untreated fruit for long term storage is happening now. Fruit for shorter storage or direct market needs at least another week. Very close or perhaps a touch after the predicted harvest date. 

Honeycrisp (predicted harvest date: Sep. 15)

Honeycrisp fruit sampled this week showed considerably more maturity than last week. Samples were all collected from ‘first pick’ fruit and should be used to guide early picking. Fruit inside the canopy is still very green.  

Red color development has improved significantly from last week. Background color is still somewhat green in many places, look for a change to pale yellow to indicate maturity. Starch clearing was highly variable again this week, with some fruit showing significant starch clearing, while other fruit were just beginning to clear or not at all. This isn’t unusual for this variety, which has very asynchronous ripening. 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 variable this week, although earlier sites had much higher values (20 Brix), while later sites averaged 10-11°Brix. Pressures were still very good in sampled fruit this week. Fruit size is very large, even in places with a rather heavy crop. We are noticing bitter pit in most locations, which is likely related to the rainfall and fruit size. 

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. Also see Dr. Randy Beaudry’s recommendations in this week’s update. 

McIntosh (predicted harvest date: Sep. 12)

Samples of McIntosh collected this week showed advancing signs of maturity. Our samples included Linda and Ruby Mac. Red color is developing well, although dependent on stain. Ethylene was only present in significant amounts in one sample tested this week from an earlier maturity location. Starch clearing averaged 3.5 to 4.5, although it was variable. Like last week it was significant in some fruit, although other fruit still had very little clearing. Sugars are still a bit low. Pressures are still adequate but variable, averaging from 15-18 in samples we collected.  

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 long term storage, and still needs a bit more time for shorter storage or direct market in most locations, very close to our predicted harvest date. 

Empire (predicted harvest date: Sep. 25)

Fruit is developing a very nice color and size. Starch clearing is just beginning, and sugars are still a little lower than preferred. None of the fruit we tested were producing significant ethylene. Pressures are still high. This variety needs at least another week. 

Jonathan (predicted harvest date: Sep. 27)

This variety is still immature. Red color is developing nicely, but background is still green. None of the fruit collected this week was producing a significant amount of Ethylene. Sugars are still lower than ideal. Recommended pressures are 14-16 depending on the intended storage time. 

Jonagold (predicted harvest date: Sep. 27)

This variety is still immature. Red color is just beginning, and background is still very green. Ethylene was being produced in one fruit, a poor indicator of most of the crop. Sugars are still low. 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 very 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 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. Background color is still very 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 not being produced in significant amounts by and of the fruit sampled this week. Starch clearing is 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.