MSU Extension Apples

General apple harvest comments

Monday, Aug. 31, 2020, was the first week to collect apple samples from a number of orchards in east Michigan. Gala, McIntosh and Honeycrisp samples were collected. Samples were then delivered and analyzed at the Department of Horticulture Post Harvest Lab at Michigan State University.

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

Based on only one week’s worth of data, Gala are ready to begin harvest with a good spot picking. Gala maturity appears to be ahead of McIntosh. With the heat of this summer, it does not surprise me that Gala are ahead of McIntosh. Honeycrisp maturity is well behind McIntosh, with the exception of the Premier strain, which are ready for harvest.

Overall, most east Michigan growers have been bumping up their crop estimate as we have moved through summer. Most growers had several good rain events in the past week, and it’s been nice to see most apples increase in size by 0.25 to 0.375 inches in diameter as a result of these rains. Most soils have been very dry this summer. Growers that have been able to irrigate are seeing a marked increase in fruit size. Golden Delicious finish is spectacular this season.

The 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 soon to evaluate the maturity of Gala and McIntosh.

Individual variety results

Gala was sampled for the first week of the season with several strains being tested, including Imperial and Fulford. Based on this week’s data, Gala are ready for a good first picking of the largest and most mature fruit. I strongly encourage growers to leave the smaller sized fruit to allow that fruit to increase in size and mature further. The predicted harvest date for Gala for the region is Sept. 10. So, Gala are maturing ahead of our predicted harvest dates. Gala is a variety that tends to mature early in hot growing seasons like we have had this summer.

The percentage of fruit with internal ethylene levels over 0.2 parts per million (ppm) is 60% this week. Fruit are still very firm, averaging 25.6 pounds pressure and the average starch index is 4.7. We usually look for a starch index for Gala to be in the 3 to 4 range. Dry conditions in many areas may have fruit that is more advanced. While growers have heard 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.

McIntosh was sampled for the first week of the season. Based on one weeks’ worth of data, McIntosh are not ready to begin harvest but are fairly close. They are eating a bit on the green side. The predicted harvest date for McIntosh is Sept. 15. Fruit color is generally poor at this time, at 50%. The percentage of fruit with internal ethylene levels over 0.2 ppm is 60% this week. The average starch index is 3.8. We usually look for a starch index for McIntosh to be around 5.

Honeycrisp was sampled for the first week of the season. Based on one weeks’ worth of data, Honeycrisp are not ready to begin harvest. Primer is an earlier maturing strain that are ready to be harvested. The predicted harvest date for Honeycrisp is Sept. 19. Fruit color is generally poor at this time, at 37%. The percentage of fruit with internal ethylene levels over 0.2 ppm is 35%. The average starch index is 1.6 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.