MSU Extension Apples

General apple harvest comments

Monday was the third week of apple harvest to collect apple samples from a number of orchards in east Michigan to test their maturity. Gala, McIntosh, Honeycrisp and Early Fuji were sampled again this week, and new varieties added this week are Jonathan, Jonagold, Empire, CrimsonCrisp and Cortland. Samples were delivered on Monday afternoon to the Department of Horticulture Post Harvest Lab at Michigan State University and analyzed yesterday. Data was forwarded on to me last night, analyzed and the result of this effort is todays third apple harvest update for east Michigan.

Based on this week’s data, some blocks of Gala are ready for harvest and others are over-mature. McIntosh have been ready for harvest with a good spot picking. Honeycrisp have matured quickly in the past week and are now ready for a good first picking. Many growers are letting McIntosh hang for better color and are moving on to and spot picking Honeycrisp. Early Fuji maturity are a few days away from being ready to begin a good first picking.

Apples have continued to size well with recent rain events. Fruit color has continued to improve with cooler weather. Overall, most east Michigan growers have been picking out long as yields have been better than estimated a few weeks ago. Golden Delicious finish is very good this season.

The normal and predicated apple harvest dates for east Michigan continue to be a part of today’s apple harvest report. The predicted dates are a few days behind normal, but as we have started harvest, early fall apple varieties are ahead of normal by three to five days. I see this swing forward for maturity of Honeycrisp, Early Fuji and Jonagold. See the MSU Extension article, “Predicted 2020 apple harvest dates” by Phil Schwallier, for more details on how these dates are calculated.

On the apple crop pest front, woolly apple aphid, brown marmorated stink bug and San Jose scale issues continue to be seen in tree fruit crops. Bitter pit is starting to be seen this week in Honeycrisp and Jonagold. For more details on these pests, refer to a separate eat Michigan fruit crop update article being published in a separate article today.

Individual variety results

Gala harvest is moving along well, most growers are nearing an end of Gala harvest. Gala was sampled for the third week of the harvest season with several fewer samples and strains being tested this week, including Brookfield and Buckeye strains. Based on this weeks’ data, some Gala strains and sites need a few more days to mature, but most strains are overmature at this time. Most growers found 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 was Sept. 10. Most Gala matured 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.

The percentage of fruit with internal ethylene levels over 0.2 parts per million (ppm) remained at 100% this week for the second week in a row. Fruit are still very firm, averaging 19.1 pounds pressure and the average starch index is 5.0. We usually look for a starch index for long-term and controlled atmosphere 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 third week of the season. Based on last weeks’ data, some McIntosh blocks and strains were ready to begin harvest last week, and many growers began to spot pick them in the last week. Do a good first picking for color and size, and leave the smaller sized interior fruit to increase in size and color further. RubyMac are also ready to harvest. The predicted harvest date for McIntosh was Sept. 15, or yesterday, so it is maturing a few days ahead of the predicted date.

Fruit color has improved to 74% this week, up from 67% last week. The percentage of fruit with internal ethylene levels over 0.2 ppm has moved back to 35% this week. The average starch index is 4.9 this week. We usually look for a starch index for McIntosh to be around 5, and many blocks are there now.

Honeycrisp was sampled for the third week of the season. As a reminder, when I harvest samples of any variety to be tested, in this case Honeycrisp, 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 ready to begin harvest. 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 75% last week to 100% this week. Fruit color has improved to 71% this week, up from at 59% last week. The average starch index has jumped two full points to 6.6 this week from 4.6 last week.

Early Fuji was sampled for the second week of the season. Based on this weeks’ data, Early Fuji are not ready to begin harvest at this time, but are very close to being ready to begin, maybe by the end of the week for a good first picking. The predicted harvest date for Early Fuji is today, or Sept. 16. The percentage of fruit with internal ethylene levels over 0.2 ppm is 10%. Fruit color has improved to 69% this week. The average starch index is 3.8 this week, up from 2.5 last week.

Jonathan was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Jonathan are not ready to begin harvest. The predicted harvest date for Jonathan is Sept. 26. The percentage of fruit with internal ethylene levels over 0.2 ppm is 55%. Fruit color is good at 87%. The average starch index is 2.8 this week.

Jonagold was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Jonagold are not ready to begin harvest, but they appear to be only a few days from the beginning of harvest. The predicted harvest date for Jonagold is Sept. 26. The percentage of fruit with internal ethylene levels over 0.2 ppm is 33%. Fruit color is generally fair to good at 62%. The average starch index is 4.7 this week. It was a surprise to see this number so advanced.

Empire was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Empire are not ready to begin harvest. The predicted harvest date for Empire is Sept. 23. The percentage of fruit with internal ethylene levels over 0.2 ppm is 10%. Fruit color is good at 70%. The average starch index is 2.3 this week.

CrimsonCrisp was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, CrimsonCrisp are not ready to begin harvest, but they are very close to being ready. I do not have a predicted harvest date for CrimsonCrisp, but growers have thought it will mature close to the harvest dates for Jonathan and Jonagold, or around Sept. 26. However, I believe it will be ready to harvest well before that date.

The percentage of fruit with internal ethylene levels over 0.2 ppm is 100%. Fruit color is good at 82%. The average starch index is 4.4 this week, however the range of starch index is between 1.0 and 7.0, or very broad. If CrimsonCrisp matures like Honeycrisp, it may require three or four picks, like Honeycrisp.

Cortland was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Cortland are not ready to begin harvest. The predicted harvest date for Cortland is Sept. 28. The percentage of fruit with internal ethylene levels over 0.2 ppm is 50%. Fruit color is good at 82%. The average starch index is 1.1 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.