MSU Extension Apples

General apple harvest comments

This Monday, Sept. 7, was the second week to collect apple samples from a number of orchards in east Michigan to test their maturity. Gala, McIntosh, Honeycrisp and Early Fuji samples were collected. Samples were then delivered to and analyzed yesterday, Sept. 8, at the Department of Horticulture Post Harvest Lab at Michigan State University.

This is the second apple harvest report for the 2020 apple harvest.

Based on this week’s data, Gala and McIntosh are ready for harvest with a good spot picking. With the heat of this summer, Gala maturity is ahead of McIntosh. Honeycrisp and Early Fuji maturity are well behind Gala and McIntosh, with the exception of the Premier strain of Honeycrisp, which were ready for harvest last week.

There are three interesting changes in apple maturity over the last week. The first is that apple size has seen a good jump with recent precipitation. The second change is that color has improved with cooler weather. Lastly, fruit firmness has dropped almost 5 pounds in the last week. Overall, most east Michigan growers have been picking out long as yields have been better that estimated just a few weeks ago. Golden Delicious finish is spectacular this season.

The normal and predicated apple harvest dates for east Michigan follow in today’s report. The predicted dates are a few days behind normal, but as we have moved closer to harvest, early fall apple varieties are ahead of normal by five or more days or so. We will see if this swing forward holds true for Honeycrisp and later varieties. See the MSU Extension article, “Predicted 2020 apple harvest dates” by Phil Schwallier, for more details on how these dates are calculated.

Spend time in your orchard in the next few days to evaluate the maturity of Gala, McIntosh and Honeycrisp.

On the apple crop pest front, woolly apple aphid colonies are becoming more common in many apple blocks and the honeydew they produce can spoil apple finish and annoy harvesting crews. Brown marmorated stink bug trap counts are slowly increasing, but overall their numbers are lower than most falls and their fruit feeding damage is harder to find than in most seasons. Sooty blotch and flyspeck disease symptoms are not common in most commercial apple blocks. However, symptoms are common on fruit in unprotected and abandoned orchards, indicating that fungicide protection has worked fairly well this season. Trap catches for oriental fruit moth, codling moth and obliquebanded leafroller are still significant in some orchards, indicating some blocks need continued protection.

Individual variety results

Gala was sampled for the second week of the harvest season with several more samples and strains being tested this week, including Fulford, Brookfield, Royal and Buckeye strains. Based on this weeks’ data, most Gala are ready for long term and midterm storage, and many blocks ready for immediate fresh market sales. A few blocks are over mature for controlled atmosphere (CA) storage. Most growers are finding it best to do at least two pickings of Gala this season, letting the less mature interior fruit color and size more.

The predicted harvest date for Gala for the region is Sept. 10. So, Gala are maturing ahead of our predicted harvest dates by several days. Gala is a variety that tends to mature early in a hot growing season like we have experienced this summer. While growers have heard over time about different Gala strains maturing over several weeks, my experience is that most strains (with the exception of Autumn Gala) mature in about the same window and within just a few days of each other.

The percentage of fruit with internal ethylene levels over 0.2 parts per million (ppm) is 100% this week, up from 60% last week. Fruit are still very firm, averaging 19.7 pounds pressure and the average starch index is 5.2. We usually look for a starch index for long term and CA storage Gala to be in the 3 to 4 range. Dry conditions in many areas may have fruit that is more advanced.

McIntosh was sampled for the second week of the season. Based on this weeks’ data, McIntosh are ready to begin harvest, some growers started to spot pick Macs over the weekend or early this week. As is the case for Gala, do a good first picking for color and size and leave the smaller sized interior fruit to allow that fruit to increase in size and color further. Some strains, like RubyMac for example, are still eating a bit on the green side and may need a few more days to mature for immediate fresh market sales. The predicted harvest date for McIntosh is Sept. 15, so it too is maturing a few days ahead of the predicted date.

Fruit color has improved to 67% this week, up from 50% last week. The percentage of fruit with internal ethylene levels over 0.2 ppm has dropped back to 0% this week. The average starch index is 3.9. We usually look for a starch index for McIntosh to be around 5, and many blocks are there now.

Honeycrisp was sampled for the second week of the season. As a reminder, when I harvest samples of any variety to be tested, I always select the most mature fruit that I can find from several trees in a block. So, for Honeycrisp, this week’s sample consisted of the most mature red colored fruit growing in full sun. Most of the rest of the fruit on the tree is several days behind this most mature fruit.

Based on this weeks’ data, Honeycrisp are not ready to begin harvest. Primer is an earlier maturing strain that were ready to be harvested last week or so. The predicted harvest date for Honeycrisp is Sept. 19 and based on this weeks’ data, it will most likely be ready to harvest a few days ahead of this date.

The percentage of fruit with internal ethylene levels over 0.2 ppm is up from 35% last week to 75% this week. Fruit color has improved to 59% this week, up from at 37% last week. The average starch index has jumped to 4.6 this week from 1.6 last week.

Early Fuji was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Early Fuji are not ready to begin harvest at this time. The predicted harvest date for Early Fuji is Sept. 16. The percentage of fruit with internal ethylene levels over 0.2 ppm is 45%. Fruit color is generally poor, at 58%. The average starch index is 2.5 this week.

Note: Firmness is measured with a mechanical 11-millimeter wide probe inserted into the pared flesh of a fruit to a distance of 8 millimeters. Starch index is measured on equatorial cross section of an apple stained with iodine solution and rated using the Cornell University starch-iodine index chart for apples on a 1-8 scale (Predicting Harvest Date Window for Apples by Blanpied and Silsbey, Cornell Extension Bulletin 221.)

Predicted peak fresh market apple harvest dates for east Michigan

Each year we publish predicted harvest dates for many locations across the state. These predicted harvest dates are based on a long-established formula using the bloom date and temperatures for 30 days post-bloom.

The following table has predicted apple harvest dates for east Michigan. It has been expanded to include more apple varieties. It lists only one date for the entire east Michigan region, which is hard to do! You can adjust these predicted harvest dates based on your actual bloom dates or on the typical harvest dates at your farm.

These dates are an estimate and will be affected by the apple strain, rootstock, crop load, fertility, soil type and other factors including weather this season. Keep a close eye on the weekly apple harvest updates for possible revisions of these dates.

Looking for more? View Michigan State University Extension’s Apple Maturity page for regional reports throughout the state and additional resources.