MSU Extension

General comments

This is the last Michigan State University Extension apple maturity report from southwest Michigan this season. We would like to thank those growers in southwest Michigan who allowed us to gather samples from their farm for this program.

Specific apple variety comments

Golden Delicious harvest in central Berrien County is mostly over. No samples were taken this week. The predicted long-term storage harvest date for Golden Delicious in 2014 at the Southwest Michigan Research and Extension Center (SWMREC) is Oct. 3.

Red Delicious harvest in southwest Michigan is nearly done. No samples were taken this week. The predicted long-term storage harvest date for Red Delicious in 2014 for central Berrien County is Oct. 7.

Most Romes have been picked for processing. No samples were taken this week. The predicted long-term storage harvest date for Rome in 2014 in central Berrien County is Oct. 15. Target starch index for Rome is 3.0.

Ida Red tested this week are averaging 17.3 pounds firmness, about the same as last week and still in the excellent firmness zone above 16 pounds. Starch conversion index averaged 3.1, same as last week and below the 3.5 sought for more immediate sales. Based on these tests, harvest could be delayed, but starch conversion is sufficient for processing uses. Starch conversion will continue to develop slowly in fruit put into controlled atmosphere (CA) storage. A few fruit at one site were showing red pigment in the flesh. Area growers are harvesting Ida Red this week, and size is generally excellent.

Ida Red test data

The predicted long-term storage harvest date for Ida Red in 2014 in central Berrien County is Oct. 11. Target starch index is 3.5.

Fuji picked this week are averaging 18.7 pounds firmness, slightly lower than last week, and getting close to the 18-pound minimum recommended firmness for fruit intended for long-term CA. Starch conversion index jumped to 5.3 compared to 3.6 for last week and above the target of at least 3.0 for good flavor characteristics. Based on these tests, these blocks could be harvested successfully for long-term CA storage.

Water core was common in two of the five Fuji orchards sampled. If water core symptoms are mild to moderate, they typically will disappear in storage. However, when water core is severe, internal flesh breakdown can develop with extended storage. Fruit with moderate to severe water core should not be placed in CA storage, but should be marketed quickly. MSU horticulturist Randy Beaudry has written a nice guide to water core in “Watercore in Apples: Causes, concerns, detection and sorting.”

Fuji (traditional season strains) test data

The predicted long-term storage harvest date for Fuji in 2014 for central Berrien County is Oct. 25. Target starch index for Fuji is 3.0.

Braeburn picked this week are averaging 21.7 pounds firmness, about 1.5 pounds less than last week and still well in the excellent firmness zone above the18 pounds recommended for fruit destined for long-term CA. Starch conversion index averaged 3.1this week, at the target of 3.0 for excellent quality quick sales and very suitable for long-term CA storage. Background color is still noticeably green. Based on these tests, harvest of these blocks can be delayed to wait for better size, skin color, brix and eating quality, although some blocks have sufficient maturity for harvest now. Most Braeburn in the area have not yet been harvested.

Braeburn test data

The predicted long-term storage harvest date for Braeburn in 2014 in central Berrien County is Oct. 25. Target starch index for Braeburn is 3.0.

Suggested firmness and starch index levels for long-term and shorter-term CA storage for selected varieties

*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”).

Contact Bill Shane at the SWMREC, 269-944-1477 ext. 205, or 269-208-1652, if you would like to have samples from your farm tested for maturity. Statewide reports will generally be available on the MSU Apple Maturity Program and Reports page by Wednesday afternoon each week.