MSU Extension Apples

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

• 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 - For the most part, it seems that northwest Michigan dodged a bullet with yesterday’s storm (Sept. 7). We have heard reports of isolated hail across the region, but to our current knowledge, we have not heard of catastrophic hail events in any of the northwest area. There were pictures of sizeable hail in areas south of our region, and Wisconsin had reported hail the size of softballs. Many growers are breathing a sigh of relief after witnessing the cloud bank and dark skies that were reminiscent of recent years past when we did receive considerable hail that did extensive damage to tree fruits and wine grapes.

Yesterday’s event did bring significant rainfall, and the Northwest Michigan Horticulture Research Center received just under 1 inch of rain. We also had high winds with that rain that likely knocked off some apples from the trees. There is more potential rain and winds in the forecast for today, Sept. 8.

The longer-term forecast for September is warmer and wetter than normal. The weather for the next few days will be relatively warm (low 70s degrees Fahrenheit) and windy. There is some potential scattered showers forecasted for the weekend, but the weather will likely remain dry and in the low 70s. Nighttime temperatures will dip into the 50s, which should be good for coloring up fruit.

According to Jeff Andresen, the medium range guidance suggests that warm weather will return to the state for the second half of September, and temperatures will be warmer than normal. Long lead outlook also suggests warmer than normal into the fall season.

Out of curiosity, we were interested to know how the heat has impacted the accumulations of growing degree days (GDDs) in northwest Michigan compared to areas further to the south in the state. As of yesterday, the MSU Enviroweather station at the Northwest Michigan Horticulture Research Center has recorded accumulations of 3260 GDD base 42, and the Sparta Enviroweather station recorded accumulations of 3587 GDD base 42. For GDD base 50, the Northwest Michigan Horticulture Research Center is at 2164 GDD and the Sparta station is at 2424 GDD. These accumulations are closer than in most typical years.

This summer’s warm weather has moved apple maturity along quickly. Growers should be checking their fruit for maturity as it may move faster than growers anticipate or expect compared to years past.

Ginger Gold has been harvested for the 2021 season. Growers still may have some fruit in storage that will be available for farm markets.

We tested Galas for the second time this week. Fruit from the different samples is showing considerable differences in maturity. The fruit at the Northwest Michigan Horticulture Research Center is at an average of 4.1 for starch removal while the two other samples are at 1s. Again, remember that Gala can ripen more quickly in warm years as we have had in 2021. This variety can surprise us with early ripening with heat, and it can be mature before McIntosh in warm years.

We tested four samples of Honeycrisp this week, and fruit has moved along in maturity compared to last week. Color is still not excellent in our samples, but again, these predicted cooler nights and days should help improve color. There is some bitter pit showing up in Honeycrisp, especially in orchards with a light crop, which is not surprising—but there was very little bitter pit in the apple samples we tested this week.

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, we believe these will be fairly accurate.

McIntosh

We tested two samples of McIntosh again this week. Firmness has dropped since last week, which is not a surprise for this variety. However, none of the other measured parameters have moved along much since last week. Color has improved slightly but nothing notable. Starch removal has also increased, but the ranges between the samples is fairly consistent with last week. Brix has increased from last week but only by an average of 0.7 degrees. We did not more McIntosh apples on the ground this week than last week.

Honeycrisp

Honeycrisp harvest is still a few weeks away until the fruit is mature enough to begin harvest. The biggest change in measurements was in color, which is exciting as the fruit were noticeably green last week. We have improved in color from last week, but there is still a considerable range in percent color in our samples and between blocks. We hope to see more color when we sample next week. Firmness also varies between the samples, but the firmness averages are exactly where they were last week: 19lbs pressure. Starch removal improved slightly, and brix is similar to last week. We did not detect much bitter pit in our samples from this week.

Gala

We tested three samples of Gala again this week, and color on this variety has improved over last week. Our samples ranged from 50-100% red color; the fruit are looking excellent and on track to have beautiful color for 2021. Firmness in this variety is still holding exceptionally well. Starch has improved, but it is the range of starch removal that is notable this week. Our starch removal ranged from 1 all the way to overripe at 8. Growers need to pay particular attention to this variety as it matures much more quickly in hot years.

There are also likely differences between strains of Gala. The Galas at the Northwest Michigan Horticulture Research Center are Buckeye Gala, and our 10-fruit sample averaged a 4.1 starch removal. Another notable measurement again this week is the low levels of brix in Gala. We are just averaging a 10 this week with some readings still in the 8s. Overall, the Gala crop is more consistent than the Honeycrisp crop, and the crop size looks excellent across the region. Many growers used ReTain on Gala this year.

Apple maturity sampling parameters

• Color % = the visual percentage of red color from 0 to 100; 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.