MSU Extension Apples

This is the fourth 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 - With a very hot August in the books, it’s appearing as if September is getting started with some more normal average temperatures. Expect highs in the mid to upper-70s degree Fahrenheit and lows in the mid-50s. There will be a break in the humidity. In general, these few cooler nights will improve color development and quality. Precipitation (or continued irrigation) last week helped considerably with fruit size. But fruit is still a week or more ahead of average maturity, and the warm weather the past few weeks has contributed to early maturity.

Gala – Both untreated fruit and fruit treated with ReTain/Harvista are beginning to show signs of maturity. Earliest blocks may be ready by the end of this week. In side-by-side comparisons, treated and untreated fruit were very similar.

Honeycrisp – Premier Honeycrisp harvest is finished. Standard strains are showing signs of maturity. First pick may begin in seven to 10 days for earliest blocks.

McIntosh (Ruby Mac) – This variety is beginning to show signs of maturity, but harvest is a couple of weeks away.

Predicted harvest dates according to the Maturity Model in MSU Enviroweather are about 10 days earlier than normal for early varieties (Gala, Honeycrisp, McIntosh), making this week about 21 days before harvest for Honeycrisp and Gala. Based on our observations and testing, we believe that fruit is approximately seven to 10 days ahead, as predicted.

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

Some frost damage is evident in locations in the form of russetting, frost rings and misshapen fruit.

Ruby Mac

In samples taken this week, there are some signs of fruit beginning to mature. It will likely be a couple more weeks until earlier McIntosh strains will begin harvest. Very nice color development on most fruit - noteour samples are all Ruby Mac. Fruit are still very firm, but showing a wider range of pressure, with more mature blocks decreasing in pressure. Sugars are just beginning to increase, again with the most advanced sites increasing first. Some starch clearing has just started. A small number of fruit are producing ethylene in significant amount. Once most fruit is over the threshold of 0.2ppm, it matures rapidly.

Honeycrisp

Premier Honeycrisp harvest began and finished mostly last week.

Standard Honeycrisp harvest approaching maturity, but there is a considerable range within blocks, as is typical of this variety. In the earliest blocks, the first fruit will likely be ready in seven to 10 days. Color is still very poor: background color is still very green but beginning to change and red color development has been minimal. Cool nights in the forecast are likely to improve color considerably. Internal indicators are somewhat ahead of color development, so be sure to assess your fruit firmness, sugars, and starch, and not just pick on color this year. A number of fruit had internal ethylene production greater than 0.2ppm in our samples this week. Sugars are steadily increasing, which is an important factor for this variety. Firmness is gradually decreasing but this is less important for Honeycrisp, which is a very crisp apple, but not an overly hard apple.

Starch is beginning to clear, but keep in mind that this is a multiple pick variety. In the earliest sites, the most mature fruit is nearly ready for harvest. But most fruit is still very starchy. Starch pattern in this variety shows a considerably different pattern than other varieties. Refer to this starch chart (which uses a 1-6 scale and unique staining pattern of Honeycrisp) for maturity evaluation.

Some fruit is already very large in size, although highly dependent on crop load, which is considerably variable this season. Some frost damage is apparent in the form of russet or other damage to fruit finish. In addition, sunburn was detected in two blocks in the form of necrotic, depressed flesh tissue. Bitter pit and lenticel breakdown was detected in a couple of fruits in one location; in this location fruit was considerably larger and crop lighter than other locations.

It will be tempting to pick this variety early this season, due to the somewhat light crop. But it is important to harvest at optimal maturity to achieve good quality and minimize storage disorders.

The most recent Honeycrisp Virtual Meetup was on the topic of Harvest and Postharvest management of Honeycrisp with Dr. Randy Beaudry, Dr. Chris Watkins, and others. You can find the recording on the MSU Kaltura Mediaspace Website.

Standard Honeycrisp

Fruit sampled the week of Aug. 30, 2021:

Summary of Standard Honeycrisp samples in 2021:

Gala

Standard strains (e.g., Brookfield and Buckeye) are quickly approaching harvest and the earliest sites may be ready by the end of this week or beginning of next. In our samples, we did not detect very much difference between untreated fruit and fruit treated with ReTain or Harvista. This includes side-by-side comparisons of untreated and treated fruit within a block. Similar observations are being made across the state. This may be the result of the very warm weather over the past two weeks when most applications were made. It is possible this is the result of a small sample size and/or lower rate applications. We recommend checking blocks that have been treated to evaluate the efficacy of your applications.

Gala color and size have improved in most locations. Background color is still somewhat green. Cool nighttime weather will continue to improve red color in the coming week. A high coloring strain does not necessarily indicate earlier maturity, so it is important to pay attention to other maturity indicators.

Starch clearing is evident in most locations, but there is considerable range even within blocks. This is likely due to the mixed maturity within blocks from the extended bloom period. Cool weather may slow this down in the next week.

Ethylene production is already increasing, with over half the fruit we tested (treated and untreated) having greater than 0.2ppm. Once fruit reaches this threshold, ethylene production and associated maturity will accelerate.

There is a very good crop with excellent quality in most locations. Some frost damage is apparent in blocks in the form of russeting, lopsided fruit, and ridging.

Gala – No ReTain

Summary of Gala (No ReTain) samples in 2021:

Gala – ReTain applied

Fruit sampled the week of Aug. 30, 2021:

Summary of Gala (+ReTain) samples in 2021:

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.