MSU Extension Apples

This is the seventh apple maturity report for the 2021 harvest season. Reports are sent out every week (usually on Wednesdays), following the Michigan State University Extension fruit team apple maturity calls on Wednesday morning.

For general information about how samples are collected and processed, please refer to Apple Maturity Report #1.

• Considerations for the 2021 harvest season can be found in this article.
• 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.

How to read the maturity tables

For each variety evaluated, we provide data from our evaluations in a table. In each, a row is provided for each sample tested. This allows you to see how the varieties may be progressing in different regions or specific locations. An average is included 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. Recommended values are included for each variety at the bottom of the table. These suggested values for firmness and starch index were also published in a standalone table format. Firmness ranges encompass long and short-term storage recommendations.

Updates for this week

Weather – Happy first day of Autumn! In the Grand Rapids, Michigan, area this week, the changing of the season is noticeable in the weather. We are experiencing significantly cooler weather, with highs in the 60s and low 70s degrees Fahrenheit and lows dipping into the 40s some nights. Rainfall Tuesday evening led to accumulation of approximately 0.2 inches in Sparta, Michigan, with more or less throughout the Grand Rapids area. More rain is expected for the remainder of the week, with possible accumulation of greater than 1 inch.

Despite the cooler weather, warmer conditions leading up to harvest have resulted in early maturity and less effect of stop-drop PGR products in many locations. It is very important to be testing fruit earlier than normal to detect fruit that is maturing ahead of expected times. In our testing, we have started testing fruit considerably earlier than normal for a number of varieties. In these, we are often seeing starch clearing beginning, ethylene development, pressures dropping sooner than we would have in a normal year. Evercrisp and Fuji this week are examples.

Gala harvest is complete for untreated fruit. Many treated fruit are also finishing harvest.

Honeycrisp harvest is complete or underway now.

Jonagold, Jonathan and Empire untreated fruit are entering the harvest window over the next week.

Golden Delicious, Red Delicious and Ida Red are showing signs towards ripening and should be watched closely.

Ambrosia internal qualities show fruit are mature, but color is less than excellent.

Evercrisp, Fuji and Rome are still very immature, but showing the first signs of ripening.

Predicted harvest dates according to the Maturity Model in Enviroweather are about 10 days earlier than normal for early varieties (Gala, Honeycrisp, McIntosh). At this time, the season appears to be between five and seven days ahead of normal.

Mixed maturity is evident in most varieties and locations. Multiple picks may be needed to harvest fruit at the appropriate maturity for successful storage conditions.

Empire

This variety is entering the harvest window now or will be in the next week. Starch clearing and ethylene production are well underway. Pressures are beginning to decrease to an acceptable level in some places but are still very high in other locations—this is an important indicator for this variety, as a softer fruit typically used for processing. Sugars are in an acceptable range. Model-predicted harvest date was Sept. 22 for this variety and they seem to be coming in right on target. Fruit treated with AVG or 1-MCP is delayed as expected.

Empire sampled Sept. 20

Empire weekly averages

Jonagold

The earliest harvest window is just beginning to peak open for Jonagold. In some places, fruit is ready for processing. Color is less than excellent in most places, although a few locations or fruit at the end of rows are coloring nicely. Background color is changing from green to yellow noticeably. Harvest is expected to begin for most locations in the next week to 10 days. Model predicted harvest was Oct. 1, but we expect actual harvest to be slightly earlier where color is adequate and crop load is light

Jonagold sampled Sept. 20

Jonagold weekly averages

Jonathan

This variety is also showing signs of maturity Ethylene production is increasing in all samples, firmness is beginning to come down, and sugar content is increasing quickly. Starch clearing is very high in a few fruit, and majority of fruit are about a week or ten days ahead of the recommended window for picking. Model predicted harvest was Oct. 1, but we expect actual harvest to be very close to that day or slightly earlier as processors demands see fit.

Jonathan sampled Sept. 20

Jonathan weekly averages

Golden Delicious

This variety is very close to the harvest window and moving very quickly. Color is improving from green to yellow in most location and size is very good. Minimal red color was observed, with only a touch of blush on a few fruit. Evaluation of starch clearing, firmness, and sugars all indicate fruit is very close to harvest and should likely begin picking within the week. Flavor of fruit is also showing noticeable development. Our predicted harvest date for Goldens was Oct. 1 and that date seems to be a bit on the late side according to the fruit we are testing. Many Golden blocks have a light crop load and could ripen faster than expected. There is very little red cheek color at this time.

Golden Delicious sampled Sept. 20

Golden Delicious weekly averages

Red Delicious

This variety appears to be maturing quickly, but it will often do this and then stall out. Ethylene development is evident in many samples with some over the 0.2 ppm climacteric. Pressures, starch and sugars are just beginning to approach acceptable harvest windows. Model predicted harvest was Oct. 7 for this variety but we expect actual harvest to be slightly earlier. Keep a close eye on Red Delicious.

Red Delicious sampled Sept. 20

Red Delicious weekly averages

Idared

This variety is showing signs of maturity but still needs a little more time. Model predicted harvest was Oct. 7, but we expect actual harvest to be slightly earlier.

Idared sampled Sept. 20

Idared weekly averages

Ambrosia

This is the third week this variety was tested. Ambrosia is still a new variety for the area, and we are learning about maturity for our region. Internal qualities indicate fruit is very near harvest maturity, but color is still less than excellent. It appears to be a heavy ethylene producing apple, with many fruit producing significant amounts in our sample last week and again this week. Starch clearing is difficult to interpret, with an interesting mosaic pattern. Clearing appears to begin throughout the flesh even while some of the cortex is still not clear. Overall, this variety needs a little more time and may begin harvest as early as next week. In other areas that grow Ambrosia, they pick it about the same time as Red Delicious.

Ambrosia sampled Sept. 20

Ambrosia weekly averages

Rome

A single sample was evaluated this week to stay ahead of early-maturity fruit. Overall, Rome is still very immature. Color is developing nicely but firmness, sugars, and starch indicate it still needs more time. Model predicted harvest was Oct. 14, and we anticipate it to be close to accurate but like everything else this season, they might come in slightly earlier. There was no color bleeding in any of the Romes we sampled.

Rome sampled Sept. 20

Fuji

A few samples were tested this week to stay ahead of the early maturity that we have observed in other fruit. Overall, Fuji is still very immature. Color is still developing and pressures are high. Starch is beginning to clear. This variety does not stain well with iodine, and starch pattern fades quickly. Some internal ethylene is being produced already. Model-predicted harvest was Oct. 20, but we anticipate actual harvest date to be considerably earlier – especially if color improves.

Fuji sampled Sept. 20

Evercrisp

A few samples were tested this week to stay ahead of the early maturity that we have observed in other fruit. Overall, Evercrisp is still very immature. Very little red color development has taken place and background color is very green. This is a high ethylene producing variety, which was detected in all samples. Starch clearing is just beginning. Soluble solids are high, which is a contribution of the Fuji background.

Evercrisp sampled Sept. 20

Apple maturity sampling parameters

• % 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
• 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.
• 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.