MSU Extension

General apple harvest comments

Apples are noticeably easier to detach from trees this week, which may be due to recent hot and dry conditions that tend to speed apple maturity. The heat may also be shortening the effectiveness of stop-drop treatments.

Trap catches and damage to apple fruit by brown marmorated stink bugs and other stink bugs are increasing. Although we tend to see more stink bug activity on field edges, particularly those close to soybean and corn fields, occasionally the insect will concentrate on a few trees inside the block.

Internal water core symptoms are building in flesh of varieties such as Red Delicious, Jonagold and Honeycrisp, but still generally at a low level. Water core symptoms are associated with environmental stresses on fruit, and not necessarily just with excess or insufficient rainfall.

Data for last and the current weeks are given in the following tables and are based on samples collected from commercial orchards in the central Berrien County area. Firmness and starch ranges are the observed low and high mean values.

Two weeks ago:

Last week:

This week:

*Evercrisp readings are for a fourth leaf planting at the southwest Michigan Research and Extension Center.

Individual variety results

No new samples of Honeycrisp, Empire or Jonagold were tested this week as most area blocks have been harvested.

Golden Delicious were tested for the fourth time, with firmness this week averaging slightly lower at 16.8 pounds. Starch conversion continues to move significantly, with the average this week at 5.7 compared to 4.4 last week—3.0 or above is considered mature. The area brix average is 14.0, about the same as last week. Harvesting of area Goldens is continuing this week, but a few blocks have not yet been touched by harvesters. The central Berrien County predicted harvest date is Sept. 19. Long-term controlled atmosphere (CA) storage is best when fruit are internally mature and firmness is 17 pounds or greater.

Red Delicious firmness continues to slowly decline, with the average this week at 16.8 pounds compared to 17.6 for last week. Starch conversion has jumped from 3.0 for last week to an average of 4.5 for this week. A starch reading of 3.5 or greater is consider sufficiently mature for harvesting. The predicted peak harvest date for Red Delicious in central Berrien County for 2017 is Sept. 22, which seems fairly accurate. Internal apple flesh water-soaking is starting to show up in more mature blocks.

Traditional late-season Fuji were sampled for the first time this week, averaging 17.1 pounds firmness, starch conversion of 4.6 and brix of 13.4. A minimum of 3.0 for the starch index is recommended for harvesting for fresh. Since the firmness is still above 16 pounds, the recommended minimum firmness for long-term CA storage, harvest can be delayed to wait for better size, brix and skin color. The predicted harvest date for Fuji for central Berrien County in 2017 is Oct. 15—this week’s tests suggest Fuji in the area will be ready ahead of that date.

Ida Red were sampled for the first time this week, with firmness testing at 16.3 pounds, starch conversion at 2.8 and brix at 12.8. Minimum recommended firmness for long-term CA storage is 16 pounds, with 3.5 internal starch considered mature. According to our tests, Ida Red intended for shorter storage and earlier utilization can be left on the tree longer to wait for better size.

Two Cameo varieties at the Southwest Michigan Research and Extension Center were tested this week, with firmness currently averaging 17 pounds and starch conversion at 4.2. We do not have specific guidelines for maturity for this variety, but if we use those for Red Delicious, they would be considered mature for long-term CA storage.

Evercrisp is a new late maturing variety from the Midwest Apple Improvement Association. Samples taken from the variety trial at Southwest Michigan Research and Extension Center tested 3 on starch conversion this week, firmness at 19 pounds and skin color still green-brown and a starchy taste. This variety typically harvests in mid-October in southwest Michigan, based on limited experience.

Predicted peak fresh market apple harvest dates

The normal and estimated 2017 peak harvest dates for apple varieties in southwest Michigan table is included here as general guidelines. Predicted harvest dates for early season apple varieties are 10 to 15 days ahead of normal due to warm temperatures in the month following bloom. Light crop and earlier dry conditions have also advanced maturity. These dates are an estimate and will be affected by the apple strain, rootstock, crop load, fertility, soil type and other factors including current weather.

*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.