MSU Extension Apples

General apple harvest comments

Growers are harvesting McIntosh and Jonathan. A few growers are finishing the final picking of Honeycrisp, but most are harvested. Most Early Fuji blocks have been harvested as well. Based on this week’s apple maturity data, SnowSweet, Jonagold and even some Golden Delicious blocks are ready for harvest. Empire, Cortland, Red Delicious and Crispin tested to be immature at this time. More details on the maturity of each of these varieties follow.

This week was the third 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 has risen from three varieties the first week to seven varieties last week to 11 varieties this week. This list of varieties tested this week includes McIntosh, Honeycrisp, Early Fuji, Empire, SnowSweet, Jonathan, Jonagold, Cortland, Golden Delicious, Red Delicious and Crispin.

There continues to be a widespread of maturity of individual apples on the tree. This may change once we get into harvest further. If this trend continues, it will mean growers will need to do multiple picks for many varieties. With continued warm to hot daytime temperatures and the lack of cold nighttime temperatures, fruit color is generally poor at this time. A number of blocks are seeing lenticel rot and black rot symptoms.

Here is the link for the 2018 Predicted Harvest Dates article that was posted to the MSU Extension in July. A list of predicated harvest dates for east Michigan is listed at the end of this article as well. I encourage apple growers to spend time in your orchard every few days to evaluate the maturity of your apple varieties.

Individual variety results

McIntosh was sampled for the third week of the season. Based on three weeks of data, McIntosh are ready for harvest and are eating much better this week. I found some blocks had been harvested in the last week. The predicted harvest date for McIntosh was Sept. 7. McIntosh are mature much later than this date. Fruit color remains generally poor at this time. The average starch index has moved from 3.5 last week to 4.1 this week.

Honeycrisp was sampled for the third week of the season. In last week’s report, I shared they were mature to over-mature. Most blocks were picked for the third or fourth and final time in the past week. For blocks that were not harvested prior to the past weekend saw a good amount of fruit drop. This week’s sample was treated with Retain, so its maturity was lagging other blocks.

The predicted harvest date for Honeycrisp was 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.

Again this block was treated with Retain. The percentage of fruit with internal ethylene levels over 0.2 parts per million (ppm) has risen from 93 percent last week to 100 percent this week. Fruit color is about the same averaging 55 percent. Fruit firmness is nearly unchanged from 14.7 pounds last week to 14.8 pounds this week, and the average starch index has moved from 6.4 last week to 6.7 this week.

Early Fuji was sampled for the second week of the season. Based on last week’s data, they were ready for harvest last week, and this week’s data confirms this. The predicted harvest date for Early Fuji was Sept. 9, but it was ready for harvest a few days earlier.

There is a good amount of fruit with internal ethylene levels over 0.2 ppm. Fruit color was the same at 59 percent, fruit firmness dropped from 16.5 pounds last week to 16.0 pounds this week and the starch index rose to 6.1 this week. The brix or sugar content is 13.9 percent.

Empire was sampled for the second week of the season, and like McIntosh matured, they are slowly and steadily moving toward maturity. Based on this week’s data, Empire are still not ready to begin harvest. The predicted harvest date for Empire was yesterday, or Sept. 18. The fruit color is fairly good and remains about the same at 69 percent, and the starch index is up from 1.7 last week to 2.4 this week. There are still eating green at this time.

SnowSweet is a fairly new variety for many east Michigan apple growers. I was able to find two farms growing it with trees mature enough to have a good crop, so I have added it to the list of varieties being tested this season. It was sampled for the first week of the season. It is reported to be ready for harvest two weeks after Honeycrisp, but based on this one snapshot of data, it appears to be ready earlier.

Based on only one week of data, SnowSweet are ready to begin harvest. The fruit color is OK at 60 percent, fruit firmness averaged 18.0 pounds and the starch index is 6.6. The fruit are very sweet, with the brix averaging 14.9 percent.

Jonathan was sampled for the second week of the season. Based on this week’s data, some strains and sites are ready for harvest at this time, while others need a few more days to mature. The predicted harvest date for Jonathan is Sept. 21. There is a good amount of fruit with internal ethylene levels over 0.2 ppm, at 70 percent this week. Fruit color has dropped to 89 percent this week, fruit firmness dropped from 20.5 pounds last week to 18.2 pounds this week, and the average starch index rose to 3.8 this week. However, the range of starch index is from 2.1 to 5.3. The brix or sugar content is 13.5 percent. Most blocks are eating a bite on the green side at this time.

Jonagold was sampled for the first week of the season. Based on only one week of data, Jonagold are ready to begin harvest. The predicted harvest date for Jonagold is Sept. 21, and it appears from this week’s data that it was ready to harvest earlier. The fruit color is OK to good for Jonagold at 47 percent, fruit firmness averaging 16.6 pounds and the starch index averaged a surprising 5.3, with a range of 4.1 to 6.2. Some Jonagold blocks may be over mature for long-term storage.

Cortland was sampled for the second week of the season, all blocks tested were Redcort. Based on this week’s data, Cortland are still not ready to begin harvest. The predicted harvest date for Cortland is Sept. 22, but I doubt that they will be mature by this date. The fruit color is good for this time of the season at 71 percent, but the starch index has risen from 1.1 last week to 2.6 this week. There are still eating very green at this time.

Golden Delicious was sampled for the first week of the season. Based on only one week of data, some blocks may be ready to begin harvest for fruit destined for long-term and CA storage. Other blocks will be ready fairly quickly. They are much further along than I thought they would be. The predicted harvest date for Golden Delicious is Sept. 23, just four days away. The fruit color or blush was not present on Monday of this week, the fruit firmness was only 17.0 pounds and the starch index averaged 3.6, with a range of 3.0 to 4.3. There are eating on the green side at this time.

Red Delicious was sampled for the first week of the season and was a limited sampling to get an early read on its maturity. Based on only one week of data, Red Delicious are not ready to begin harvest, but are much further along than I thought they would be for this time of the season. The predicted harvest date for Red Delicious is Sept. 29. The fruit color is good at 99 percent, fruit firmness averaged 17.2 pounds and starch index averaging 3.7. There are eating very green at this time. I will be expanding Red Delicious sampling next week.

Crispin or Mutsu was sampled for the first week of the season to get an early read on its maturity. Based on only one week of data, Crispin are not ready to begin harvest. The predicted harvest date for Crispin is Oct. 6. The fruit color is still very green, with the starch index of 2.3. I have not seen any blister spot showing yet in Crispin. 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.