MSU Extension Apples

General apple harvest comments

Monday was the fifth week of apple harvest to collect apple samples from a number of orchards in east Michigan to test their maturity. Jonathan, Jonagold, Empire, Cortland, Golden Delicious, Red Delicious and Idared were sampled again this week, and new varieties added this week are Northern Spy, Crispin and EverCrisp to get an early read on their maturity. On Monday afternoon, these samples were then delivered to the Department of Horticulture Post Harvest Lab at Michigan State University and analyzed yesterday. The raw data was forwarded on to me last night, analyzed further and the result of this effort is today’s fifth east Michigan apple harvest update.

Based on this week’s data, Jonathan and Jonagold are starting to be overmature. Most Empire and some Golden Delicious blocks are ready for harvest. Honeycrisp were not tested this week, but I did eat a good number of them on Monday from several orchards when I was collecting other varieties. Some growers are waiting for the last/third or fourth picking to get better color on Honeycrisp. They have matured quickly in the past week; most fruit are starting to soften and eat as being overmature. Color has only improved slightly in Honeycrisp in the past week.

Most growers are about halfway through apple harvest. Apples have continued to size well this season, with most varieties picking out long. Fruit color has continued to improve with cooler weather. Golden Delicious finish is very good this season. The average brix or sugar levels have taken another good jump in the past week.

Demand for fresh apples at farm markets, farmers markets and pick your own sales have been outstanding so far this fall, with record sales for this time of the season. Sweet cider continues to taste better as brix or sugar levels have increased and more varieties are available to be added to “the blend.” Demand for sweet cider has also been very strong this fall.

Many growers are finding their storages are rather empty for this time of the season. This has not been the result of poor yields, but more the result of increased demand for fresh market sales and high demand for cider and processing apples. Many growers report having either not enough or just enough cider apples to keep up with the strong demand.

Bitter pit is continuing to be seen this week in late harvested Honeycrisp, Jonagold, Red Delicious and Northern Spy. Blister spot is starting to be seen this week in Crispin or Mutsu.

The normal and predicated apple harvest dates for east Michigan continue to be a part of today’s apple harvest report. The predicted harvest dates are based on temperatures from spring to 30 days after bloom and do not take into account summer temperatures, which can push development earlier or later than predicted. Keep in mind these predicted dates are for peak harvest, so some fruits might be ready ahead or behind these dates as we move through maturity.

These predicted harvest dates are a few days behind normal or most years, but as we are continuing with harvest many apple varieties are ready to harvest a few days ahead of normal. 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, brown marmorated stink bug (BMSB) trap catch numbers collected Monday and Tuesday, Sept. 28 and Sept. 29, have been high in about a third of the 10 orchards where I monitor traps. Most of this high trap catch occurred last Wednesday through Friday. For the rest of the orchards, trap catch has continued to be lower than normal for this time of the season. For these BMSB hot spots, use a border spray to control them on late season varieties. Consult insecticide labels or the Michigan Fruit Management Guide (E-154) for products with low preharvest intervals. For the other trap sites and farms that don’t monitor for BMSB, do a good job of scouting for the adults and nymphs as well as damage to fruit.

Individual variety results

Jonathan was sampled for the third week of the season. Most Jonathan blocks were ready to begin harvest last week, and based on this week’s data, Jonathan maturity has continued to move forward. The predicted harvest date for Jonathan was Sept. 26, so it is maturing either ahead of or very close to this date. The percentage of fruit with internal ethylene levels over 0.2 parts per million (ppm) is up slightly to 65%. Fruit color is excellent at 99%. The average starch index is 4.4, up from 3.5 last week, with the brix or sugar level at 14.4%. Unharvested Jonathan blocks need to be harvested soon.

Jonagold was sampled for the third week of the season. Like Jonathan, most Jonagold blocks were ready to begin harvest last week, and based on this week’s data, Jonagold maturity has continued to move forward quickly. All Jonagold blocks sampled this week are overmature. In last week’s report, I stated that Jonagold were ready to begin harvest. The predicted harvest date for Jonagold was Sept. 26, so they were ready to harvest a few days ahead of that predicted harvest date. The percentage of fruit with internal ethylene levels over 0.2 ppm is up from 58% last week to 93% this week. Fruit color is still generally fair to good at 62%. Color has not improved a great deal in the past week. The average starch index is up from 4.7 last week to 6.0 this week. Some bitter pit is being seen on the late harvested Jonagold.

Empire was sampled for the third week of the season. Based on this weeks’ data, the harvest window for Empire is just opening, with some Empire blocks being ready to begin harvest while others still needing a few more days to mature. The predicted harvest date for Empire was Sept. 23, so they are maturing later than this date. The percentage of fruit with internal ethylene levels over 0.2 ppm is still low at 23%. Fruit color is good at 86%. The average starch index is up from 2.9 last week to 3.2 this week. I generally look for a starch index above 3.5 to begin Empire harvest.

Cortland was also sampled for the third week of the season. Based on this weeks’ data, Cortland are still not ready to begin harvest. The predicted harvest date for Cortland was Sept. 28, so they are maturing well behind this date. Again, they are not mature. The percentage of fruit with internal ethylene levels over 0.2 ppm is 70%. Fruit color is excellent at 90%. The average starch index is up from 1.7 last week to 2.1 this week. Some growers have picked a few of the most mature Cortland for sweet cider from the tops or shell of the tree, but they are too green to add much to the flavor of cider.

Golden Delicious was sampled for the second week of the season. Again this week, all of the samples tested were the Smoothee strain. Based on this weeks’ data, many Golden Delicious blocks are ready to begin harvest. The predicted harvest date for Golden Delicious is Oct. 1, or tomorrow. Many blocks are maturing a few days ahead of this date. The percentage of fruit with internal ethylene levels over 0.2 ppm is up from 10% last week to 32% this week. Fruit color or blush is good for Goldens, this week about the same at 23%. The average starch index is up from 1.9 last week to 3.9 this week. I generally look for a starch index to be at 3.0 to begin Golden harvest. The finish on Goldens is excellent this season, maybe the best I have ever seen.

Red Delicious was sampled for the second week of the season, with the number of Red Delicious samples ramped up to get a good read on its maturity. The number of strains was also broadened to include Scarlet Spur, Red Chief, Miller Spur and Bright-N-Early strains. Based on this weeks’ data, Red Delicious are not ready to begin harvest. The predicted harvest date for Red Delicious is this Saturday, Oct. 3. They will not be mature by this date.

The percentage of fruit with internal ethylene levels over 0.2 ppm is up from 7% last week to 56% this week. Fruit color is excellent at 94%. The average starch index is up slightly from 2.0 last week to 2.4 this week. I usually look for a starch index to be 2.5 to 3.0 to begin to see the harvest window open. Red Delicious are still eating very green. By this time next week, they may be ready to begin harvest. Some bitter pit is being seen in Red Delicious in the last week.

Idared was sampled for the second week of the season. Based on this weeks’ data, Idared are not ready to begin harvest. The predicted harvest date for Idared is Oct. 9. The percentage of fruit with internal ethylene levels over 0.2 ppm is up dramatically from 10% last week to 70% this week. Fruit color is good at 83%. The average starch index is 1.7 this week. I generally look for a starch index to be to 3.5 to begin to see the harvest window open.

Northern Spy was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Northern Spy are not ready to begin harvest. The predicted harvest date for Northern Spy is Oct. 10. The percentage of fruit with internal ethylene levels over 0.2 ppm is 76%, which is typical for Spy’s to be a good ethylene producer. Fruit color is only fair at 52%. The average starch index is 2.1 this week, which is higher than I would have expected for this time of the season. Some bitter pit is being seen this week in Northern Spy.

Crispin or Mutsu was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, Crispin are not ready to begin harvest. The predicted harvest date for Crispin is Oct. 13. None of fruit sampled had internal ethylene levels over 0.2 ppm. Fruit color or blush is only at 14%. The average starch index is 2.0 this week, which is higher than I would have expected for this time of the season. Blister spot was seen this week for the first time in Crispin.

EverCrisp was sampled for the first week of the season to get an early read on its maturity. Based on one weeks’ worth of data, EverCrisp are not ready to begin harvest. The predicted harvest date for EverCrisp is Oct. 21. The percentage of fruit with internal ethylene levels over 0.2 ppm is 100%. Fruit color is good at 78%. The average starch index is 2.0 this week, which is higher than I would have expected for this time of the season. The brix is at 17.5%, which is an amazing high number for this early in the season for EverCrisp. I am hoping to find more EverCrisp blocks to sample for next week.

Apple maturity sampling parameters

• % fruits with internal ethylene over 0.2 ppm = indicates when ethylene begins to influence fruit ripening and it cannot be held back easily after this is reached.
• Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested.
• Firmness lbs. = pounds pressure sampled from two sides of each fruit.
• Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. The higher the number, the more mature fruit is, using the Cornell Starch Iodine Index Chart.
• Brix % = % sugar. 

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.

We are grateful to many farms and organizations who make the 2020 east Michigan apple maturity program a success, either through direct funding or indirectly through cooperation.

• Erwin Orchards, S. Lyon, Michigan
• Hy’s Cider Mill, Romeo, Michigan
• Spicer Orchards, Fenton, Michigan
• Westview Orchards, Romeo, Michigan
• Many other orchards where apple samples are collected
• Michigan State Horticultural Society
• Michigan Tree Fruit Commission
• Michigan State University Department of Horticulture
• Michigan State University AgBio Research
• Michigan State University Extension

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