MSU Extension Apples

This is the fourth 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

Again this week, we have had some unusual weather across the region. As predicted by Michigan State University’s Jeff Andresen, September 2021’s weather will be warmer and wetter than normal, and thus far, those predictions have been accurate. For the most part, daytime temperatures have been in the 70s degrees Fahrenheit for this past week. However, we did hit 80 F on Saturday, Sept. 11. Thankfully, nighttime temperatures have been cooler in the mid- to low 50s, and we hope these cooler nights will help improve color. Color is quite variable by variety, but for northwest Michigan, a region where we typically have excellent color, we could sure use some more of those cooler conditions to color up the fruit.

The forecast is for continued warm in the daytime, and nighttime temperatures are only predicted to drop into the high 50s and low to mid-60s. By the end of the weekend and into the start of next week, we will see hot weather move back into the region, and we will have another dose of summer. So far this season, we have accumulated 3499 growing degree days (GDD) base 42 and 2324 GDD base 50. In addition to warm weather, we have seen a lot of rainfall over the past week.

According to the Northwest Michigan Horticulture Research Center’s Enviroweather station, there have been seven rainfall events since last Saturday. We received just under and over 0.1 inch of rain last Saturday and Sunday (Sept. 4-5). We received just under 1 inch of rain on Tuesday, Sept. 7, and lighter rainfall on Wednesday, Thursday and Friday (Sept. 8-10): 0.18 inch, 0.08 inch and 0.09 inch. We had more rain Sept. 14 and as of 1 p.m. Sept. 14, the Enviroweather station recorded 0.61 inch so far.

The most noticeable thing about the 2021 rain events have been their intensity and duration. For the most part, rain events have been significantly intense with lots of water in a short amount of time. We have had significant wash out events in orchards, farm roads, county roads and potential flash flood warnings across the region. Rainfall totals for many of these events have been minimal, but again, the rain has come in the form of heavy downpours.

There is more potential rain in the forecast on Friday and into Saturday (Sept. 17-18). Rain events and even sunny days have been accompanied by higher-than-normal winds. These weather conditions have posed challenges for apple harvest.

We tested Galas for the third time this week. Fruit from the different samples is again showing considerable differences in maturity, similar to last week. We harvested the Gala at the Northwest Michigan Horticulture Research Center this week and will finish up later this week as our Gala were testing in the 4-5 range for starch removal. The Galas at the Northwest Michigan Horticulture Research Center are eating pretty well given that the brix levels of almost all Gala samples are still much lower than we would expect for this time of year and with the advanced maturity in other parameters we measure. 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 was more bitter pit in Honeycrisp this week compared to past weeks.

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 remained the same compared with last week. Color has improved somewhat, but all the samples of this variety still had a pronounced green background color. Starch removal readings increased from 2.5 to 3.0 this week, but there is still a range in starch removal measurements. Brix in McIntosh has remained consistent over the past three weeks. Again, in this variety, we see a range of brix readings, and some are still in the 9 range. This apple is still tart, but the starchiness is not as pronounced as in past weeks.

Honeycrisp

Honeycrisp spot picking has begun in more southerly areas of the region. Color is still a major concern as we typically have great color in northwest Michigan, and fruit have been slow to color this season. Firmness also varies between the samples, and we have seen drops in firmness from last week. In one sample collected from the Northwest Michigan Horticulture Research Center, we noted a huge drop in firmness; in all of our samples from our back block, the firmness ranged from 14-18, with the majority of samples are in the 15-16 range.

In addition to the low firmness levels, starch removals are showing that the fruit are mature, which is concerning given the relatively poor color in this particular block. Other Honeycrisp samples still have higher firmness measurements, but overall firmness averages fell just under 2 pounds pressure from last week. Starch removal also increased by one, but the ranges in removal readings were from 1.5-6 this week.

Brix did improve slightly over last week, but we still have a surprising number of samples with brix levels in the 9 degrees range. As mentioned above, we have observed more bitter pit showing up in our samples compared to last week.

Gala

We tested three samples of Gala again this week, and color on this variety has improved over last week; color increased from 73% to 82%, but a range is still notable from 60-100% red color. Firmness in this variety is still holding exceptionally well again this week, and we see only a small drop in firmness from past weeks. Starch removal has remained constant compared with last week, and brix is also similar to our readings last week. We are quite surprised we have not seen an increase in % brix in Gala. The apples we tested were again quite low in brix content, and the lack of sugars in the fruit is apparent when you eat them. We hope that the coming weeks will help increase brix levels in all varieties.

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.