MSU Extension

This will be the last apple maturity report for the southwest Michigan region this season. Apples are maturing early this season, as predicted by the maturity models. Reports from other regions will continue for the next few weeks and can be found at Michigan State University Extension’s Apple Maturity page.

We greatly appreciate the support of local growers who provided apple samples for testing, the MSU apple maturity team and the Michigan Apple Committee.

General apple harvest comments

Brown marmorated stink bug ended up being a relatively minor pest on apples in southwest Michigan this year. Damage to apple fruit close to harvest by this bug may show up later in storage, as can bitter pit and sooty mold.

Some Red Delicious and Golden Delicious still remain to be picked for short-term local sales or juice. Harvests have been delayed for some older, poorer coloring strains of Fuji and Braeburn; growers are waiting for better skin color. A few very late-season varieties such as Goldrush, Wealthy and Pink Lady still remain to be picked.

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. 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:

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

This week:

Individual variety results

Sampling of Golden Delicious, Red Delicious, Cameo and Evercrisp were not tested this week, as they have already reached full maturity last week or earlier.

Late-season Fuji varieties have retained firmness over the past three weeks, currently averaging 16.9, but starch conversion has gone from 4.7 last week to 5.8 this week and brix from 13.4 to 14.4. A minimum of 3.0 for the starch index is recommended for harvesting for fresh. Skin color has improved compared to last week.

Since the firmness is still above 16 pounds for some orchards, the recommended minimum firmness for long-term controlled atmosphere (CA) storage, harvest in those orchards 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 about 1 pound softer, now at an average of 14.8 pounds. Starch conversion is much higher, now at 5.7 (compared to 3.9 for last week), and brix at 13.7. Minimum recommended firmness for long-term CA storage is 16 pounds, with 3.5 internal starch considered mature. Most Ida Red tested this week are best suited for short-term storage and relatively quick utilization.

Rome apples tested this week are still relatively firm, now averaging 20.5 pounds and starch conversion tests at 3.9. Starch tests of 3 or above are considered internally mature. Most Romes in the area have already been picked for processing uses.

Braeburn has not changed much in the past week, with firmness now testing at 20.7 pounds. Starch conversion is slightly higher at 4.5, and brix is slightly higher now at 13.2. Fruit with starch conversion values greater than 3.0 are considered internally mature, but flavor and appearance will improve by delaying harvest.

The predicted peak harvest date for Braeburn for central Berrien County is Oct. 15, five days ahead of the long-term average. Red skin color of Braeburn develops late in the season and is highly dependent upon nitrogen level and light penetration within the canopy. Harvest maturity should be determined by ground color rather than red skin color.

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 five 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.