MSU Extension Apples

General apple harvest comments

Growers are working hard at Gala and Honeycrisp harvest. Based on this week’s apple maturity data, Gala, Honeycrisp and Early Fuji are ready for harvest. Further, some Honeycrisp blocks tested this week are over-mature. Also, some early maturing McIntosh strains are just a few days away from being ready for harvest, however fruit color on McIntosh is generally fair to poor at this time. Empire, Jonathan and Cortland tested to be immature. More details on the maturity of each of these varieties follow.

This week was the second week of our apple harvest season to collect apple samples from a number of orchards in east Michigan and to have them analyzed at the Department of Horticulture Post Harvest Lab at Michigan State University. The number of varieties tested this week rose from three varieties last week to seven this week. This list includes the following varieties: Gala, McIntosh, Honeycrisp, Early Fuji, Empire, Jonathan and Cortland.

Thus far this season it appears there is a widespread of maturity of individual apples on the tree. This may change once we get further into harvest. If this trend continues, growers will need to do multiple picks on many varieties. Fruit color is generally poor at this time, mainly due to the heat of the last several weeks and the lack of cold night time temperatures.

View the 2018 predicted harvest dates. A list of predicated harvest dates for east Michigan is listed at the end of this article. Spend time in your orchard soon to evaluate the maturity of your apple varieties.

Individual variety results

Gala was sampled for the second week of the season, with several strains being tested. The predicted harvest date for Gala for the region was Sept. 5. Based on this week’s data, Gala is ready for harvest. As I said in last week’s report, some Gala blocks were ready on that date. Gala is a variety that tends to mature early in hot growing seasons, such as this season.

The percentage of fruit with internal ethylene levels over 0.2 parts per million (ppm) has risen from 45 percent last week to 75 percent this week. Fruit are still firm averaging 18.7 pounds pressure and the average starch index has moved from 3.1 last week to 5.7 this week. Dry conditions in many areas have slowed fruit sizing and color has improved a bit to 81 percent. Do a strain and block-by-block sampling to determine which are mature, and in most cases, do two pickings to get the earliest maturing fruit off the tree.

McIntosh was sampled for the second week of the season. Based on two weeks of data, some early maturing McIntosh strains and sites are ready to begin harvest in the next few days, however most blocks need more time to begin harvest. The predicted harvest date for McIntosh was Sept. 7. So, McIntosh will be mature after this date.

Fruit color is generally poor at this time, raising from 52 percent last week to 62 percent this week. The percentage of fruit with internal ethylene levels over 0.2 ppm has risen from 5 percent last week to 45 percent this week. The average starch index has moved from 2.5 last week to 3.5 this week. There has been some fruit drop in McIntosh, but most of the fruit has been pushed off the limb from growth rather than dropping on its own accord.

Honeycrisp was sampled for the second week of the season. Recall that when I take a sample of any variety, I sample the most mature fruit on the tree. So, in the case of Honeycrisp, this is the few fruits per tree that have a bright red color—what I call “stop light” color—with the background color changing from green to yellow. The predicted harvest date for Honeycrisp is today, Sept. 12. This season, most Honeycrisp blocks were mature before this date. As is the case for Gala, Honeycrisp is another variety that tends to mature early in hot growing seasons, such as this season.

Based on this week's data, Honeycrisp is ready for a good picking, harvesting only the stop light red colored fruit and waiting for the green fruit to mature for another four to six days. Some blocks tested to be over-mature, with starch averaging 7.5.

The percentage of fruit with internal ethylene levels over 0.2 ppm has risen from 80 percent last week to 93 percent this week. Fruit color is about the same, averaging 61 percent. Fruit firmness has dropped from 15.4 pounds last week to 14.7 pounds this week. The average starch index has moved from 4.8 last week to 6.4 this week. Honeycrisp always require three to four pickings. The fruit that is ready is eating well.

Early Fuji was sampled for the first week of the season. Based on only one week of data, they are ready for harvest now. The predicted harvest date for Early Fuji is Sept. 9. There is a good amount of fruit with internal ethylene levels over 0.2 ppm, fruit color is fair at 59 percent, fruit are firm at 16.5 pounds and the starch index is 5.7. The brix or sugar content is 13.2 percent.

Empire was sampled for the first week of the season. Based on only one week of data, Empire are not ready to begin harvest. The predicted harvest date for Empire is Sept. 18. The fruit color is fairly good for this time of the season at 67 percent, but the starch index is only 1.7. There are eating very green at this time.

Jonathan was sampled for the first week of the season. Based on only one week of data, Jonathan are not ready to begin harvest. The predicted harvest date for Jonathan is Sept. 21. The fruit color is good at 95 percent, but the starch index is only 1.9. There are eating very green at this time.

Cortland was sampled for the first week of the season, both blocks tested were Redcort. Based on only one week of data, Cortland are not ready to begin harvest. The predicted harvest date for Cortland is Sept. 22. The fruit color is good for this time of the season at 75 percent, but the starch index is only 1.1. There are eating very green at this time.

Predicted peak fresh market apple harvest dates for east Michigan

Each year we publish predicted harvest dates for three varieties for many locations across the state. This year's “Predicted 2018 apple harvest dates” were published July 10. These predicted harvest dates are based on a long-established formula using the bloom date and temperatures for 30 days post-bloom. The information in this article lists the bloom and harvest dates for Deerfield and Romeo, Michigan.

The following table has predicted apple harvest dates for east Michigan. It has been expanded to include more apple varieties and 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. Due to the early start to our growing season and much above normal temperatures this summer, I believe our actual harvest dates may be a few days ahead of these predicted harvest dates for most varieties. Keep a close eye on the weekly apple harvest updates for possible revisions of these dates.

*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.)

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