MSU Extension Apples

General apple harvest comments

Based on this week’s data from the apple maturity project, Idared, Crispin and EverCrisp are ready to harvest. The few remaining Northern Spy blocks are overmature. Braeburn and Winesap are not mature yet. Golden Delicious, Red Delicious, Rome, Autumn Gala, Cameo, Fuji and Enterprise were not sampled this week, as they tested to be mature in last week’s sampling.

This will be the last week of sampling for maturity and the final east Michigan apple harvest report for the 2020 season.

Apple harvest is progressing well for most growers, with growers reporting they will wrap up apple harvest in the next week if the good weather holds up.

Most apple varieties have continued to produce more and more internal ethylene, which is a sign of apple maturity. The average brix or sugar levels have taken another nice jump in the past week, up from an average of 15.8% last week to 16.3% this week. Bitter pit continuing to be seen in Northern Spy. Blister spot is continuing to be seen in Crispin or Mutsu. Watercore was seen this week in some EverCrisp and Winesap samples at the Michigan State University Post Harvest Lab as samples were analyzed.

Most growers are finding that their storages are emptying out quickly this season, mainly due to strong demand for fresh market apples at farm markets and from good sales for cider and processing apples.

This Monday was the eighth week of apple harvest to collect apple samples from a number of orchards in east Michigan to test their maturity. Idared, Northern Spy, Crispin, EverCrisp, Braeburn and Winesap were included in the sampling this week. On Monday afternoon, these samples were 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 evening, analyzed further and the result of this effort is today’s east Michigan apple harvest report.

Brown marmorated stink bug activity dropped back this week with cooler temperatures. The adults are moving into buildings in search of overwintering sites. Do a good job of scouting for the adults and nymphs as you are wrapping up harvest and as fruit is being graded.

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 that these predicted dates are for peak harvest, so some fruits might be ready ahead or behind these dates as they move toward 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 and Amy Irish-Brown, for more details on how these dates are calculated.

* Based on sample from one orchard

Individual variety results

Idared was sampled for the fifth week of the season. Based on this weeks’ data, Idared are finally ready to harvest. Some blocks were ready to begin harvest last week. The predicted harvest date for Idared was October 9, but they were not ready to begin harvest by that date. The percentage of fruit with internal ethylene levels over 0.2 ppm is up from 95% last week to 100% this week. Fruit color is excellent at 91%. The pressure has dropped from 16.5 pounds last week to 15.5 pounds this week. The average starch index is up from 3.2 last week to 4.4 this week. I generally look for a starch index to be to 3.5 to begin to see the Idared harvest window open.

Northern Spy was sampled for the fourth week of the season. Based on this weeks’ limited sample size and data, Northern Spy are overmature. Most Northern Spy blocks have been harvested. The predicted harvest date for Northern Spy was Oct. 10. Some blocks were ready to begin harvest on that date, while others needed a few more days to mature. The percentage of fruit with internal ethylene levels over 0.2 ppm is still at 100%, which is typical for Spy’s to be a high ethylene producer. Fruit color is only fair at 50%. The average starch index is up from 5.0 last week to 6.5 this week. There is a good amount of bitter pit is being seen this week in the remaining Northern Spy’s yet to be harvested.

* Based on sample from one orchard

Crispin or Mutsu was sampled for the fourth week of the season. Based on last weeks’ data, some blocks of Crispin were ready to begin harvest while others were still not ready. This week, remaining Crispin blocks are now ready to harvest. The predicted harvest date for Crispin was Oct. 13. I think they were ready to harvest close to this date. The percentage of fruit with internal ethylene levels over 0.2 ppm remains the same this week at 100%. Fruit color or blush is up from 21% last week to 40% this week. The average starch index is 4.1 this week, up from 3.2 last week. Brix level have taken a good jump to 17.2% this week. Blister spot continues to be seen in Crispin.

* Based on sample from one orchard

EverCrisp was sampled for the fourth week of the season. Based on this weeks’ data, EverCrisp are ready to harvest with a few blocks being overmature. The predicted harvest date for EverCrisp is Oct. 21, or today. So, they are mature just before or very close to this date. EverCrisp is a new variety for the apple maturity project, with blocks just starting to begin producing fruit. As these young blocks mature and settle down some, their maturity window may shift some to a later date. The percentage of fruit with internal ethylene levels over 0.2 ppm is 100%. Fruit color is good at 87%. The average starch index is 5.3 this week, up from 4.0 last week. The brix is at 17.9%, which is amazingly high.

Braeburn was sampled for the second week of the season. Based on this weeks’ data, Braeburn are still not ready to begin harvest. The predicted harvest date for Braeburn is Oct. 28. I believe it will be mature very close to this date. The percentage of fruit with internal ethylene levels over 0.2 ppm is 60%. Fruit color is good at 80%, with fruit remaining very firm at 24.1 pounds. The average starch index remained the same this week at 2.5.

Winesap was sampled for the second week of the season. Based on this weeks’ data, Winesap are also not ready to begin harvest. The predicted harvest date for Winesap is Oct. 30. I believe they will mature close to this date. The percentage of fruit with internal ethylene levels over 0.2 ppm is 100% this week, up from 50% last week. Fruit color is excellent at 94%. The average starch index is 2.2 this week, up from 1.4 last 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.