MSU Extension

General apple harvest comments

A bit more moldy core and water core symptoms are showing up in Red Delicious this week, but is still a relatively minor problem. Some significant fruit drop is occurring in Red Delicious orchards that remain to be picked. Most area Golden Delicious fruit have been harvested.

Colonies of woolly apple aphids are continuing to build in Northern Spy orchards.

Data for last and the current weeks given in the following tables 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. Values reported here may not be representative of orchards with heavy crop loads, heavier soils, plant growth regulator treatment or other factors affected crop maturity.

Last week:

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

This week:

*Cameo and Evercrisp values are for samples collected at the Southwest Michigan Research and Extension Center.

Individual variety results

Golden Delicious were tested for the fifth week, with firmness averaging slightly lower at 16.0. Starch conversion continues to move significantly, with a current average of 5.7 compared to 4.4 last week, with 3.0 or above considered to be mature. The brix average is 14.6 for these samples, slightly higher than last week. The central Berrien County predicted harvest date is Sept. 19. For this variety, mid-term controlled atmosphere (CA) storage is more appropriate than long term when fruit are internally mature and firmness drops to the 16 pound range.

Red Delicious firmness continues to slowly decline, with the average this week now at 16.1 pounds compared to 16.8 last week. Fruit at 16.0 or lower are considered to be appropriate for short-term CA storage and more immediate consumption. Starch conversion is now at 5.3 compared to 4.5 last 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 is Sept. 22.

Late-season Fuji varieties have not change much since last week, averaging 16.6 pounds firmness, 4.7 starch conversion and 13.4 brix. 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 is Oct. 15.

Ida Red firmness tested this week at 15.7 pounds, starch conversion at 3.9 (compared to 2.8 last week) and brix at 12.8. Minimum recommended firmness for long-term CA storage is 16 pounds, with 3.5 internal starch considered mature. Ida Red that will be stored for later use would benefit by being harvested relatively soon.

Cameo maturity in the Southwest Michigan Research and Extension Center variety trial did not change much since last week, and currently have firmness 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 internal maturity has improved greatly as indicated by a starch test of 7.0 this week compared to 3.0 last week. Firmness is still high at 18.3 pounds with skin color improving. This variety is known for high brix levels, currently testing 16.3. Our best guess is this variety harvests about 15 days after Red Delicious, or approximately Oct. 6 for central Berrien County. Fruit maturity is affected greatly by crop load—fruit from trees with heavier loads are considerably behind those reported here.

Rome apples tested this week were relatively firm at 21.3 pounds and starch conversion tests at 3.0. Starch tests of 3 or above are considered internally mature. Most Romes in the area have already been picked for processing uses.

Predicted peak fresh market apple harvest dates

The normal and estimated 2017 peak harvest dates for apple varieties in the 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.