MSU Extension

This is a weekly Michigan State University Extension apple maturity report for southwest Michigan from early September until mid-October. The samples for these reports are collected primarily in Berrien and Van Buren counties. Sites north of here, closer to Lake Michigan, on heavier soils or with heavy fruit loads will generally harvest later.

Reports from the current and past years for southwest Michigan and other regions are posted at the MSU Apples website.

General comments

Current cooler weather has noticeably improved red coloration of Gala, Honeycrisp, Empire and Jonagold. Growers are setting out bins getting ready for main season Golden Delicious and Red Delicious harvest. Brix levels have been a bit lower than normal, perhaps due to recent rains that increase the water content.

According to the brown marmorated stink bug (BMSB) report for Sept. 12, 2014, a total of 25 nymph and 23 adult brown marmorated stink bugs were captured in traps at seven out of the 77 sites being monitored. This is up from last week, but still lower than what we were finding this time last year. Sites where we captured BMSB this week include two orchards in Berrien County, one apple and one peach, and five urban or roadside sites near soybean fields in Berrien, Lenawee and Ingham counties. No damage to fruit crops has yet been reported. Homeowners near Stevensville in Berrien County are also beginning to report BMSB on sides of their houses in greater numbers this week. Look for them on the soffit or under the eaves where they may be aggregating and searching for places to overwinter.

Specific apple variety comments

Gala harvest is in the second week in southwest Michigan. Firmness average is 19.2 pounds, down 1 pound from last week. Starch conversion average moved from 4.1 last week to 4.8 for this week. The target for long-term controlled atmosphere (CA) storage is a starch conversion of at least 3.0 and ideally with firmness of 18 pounds or more.

Galas maturity summary

The predicted long-term storage harvest date for 2014 for the Southwest Michigan Research and Extension Center (SWMREC) is Sept. 7. The long-term normal harvest date for Gala in Berrien County is Sept. 8. Target starch index is 3.

Honeycrisp samples are testing an average of 15.9 pounds, close to the recommended firmness of 16 pounds and starch index of 3.5 for mid-term CA storage. Red skin color looks nice on sandy sites. Flavor has improved noticeably as the starchy taste has disappeared. Harvest is ongoing. Demand has exceeded supply.

Honeycrisp maturity summary

The predicted long-term storage harvest date for Honeycrisp in 2014 for SWMREC is Sept. 19. Some blocks are ahead of the predicted harvest date. Target starch index for Honeycrisp is 3.5.

Jonagold samples are averaging 18 pounds, above the recommended firmness of 17 pounds and slightly below the starch index of 3.5 recommended for long-term CA storage, but one block with an average of 5.4. Red skin color is excellent on newer strains such as Rubinstar, but still significantly green on older strains such DeCoster. Some Jonagold have been harvested for apple pie slices.

Jonagold maturity summary

The predicted long-term storage harvest date for 2014 for SWMREC is Oct. 1, 2014. Target starch index for Jonagold is 3.5.

Jonathan samples (two locations) are testing 17 pounds; the threshold of minimum firmness for long-term CA storage is 16 pounds. The good firmness allows harvest to be delayed to wait for bigger size and more sugar. Starch indices are averaging 3.1, which is close to the target maturity of 3.5 for optimal long-term CA storage for apples intended for fresh market sales.

Jonathan maturity summary

The predicted long-term storage harvest date for Jonathan in 2014 for SWMREC is Oct. 1. Target starch index for Jonathan is 3.5.

A few Golden Delicious from the area were spot-checked and showed some slight evidence of starch conversion (starch conversion readings of 1 to 1.8). Some blocks intended for apple pie slice processors who are less concerned about brix will be harvested this week.

A few blocks of early coloring Red Delicious strains such as Earlichief and Schlect are slated to be picked soon, but maturity tests should be used to verify if they are really ready.

Empire (not tested) has a predicted long-term CA storage harvest date of Sept. 23 in central Berrien County.

Suggested firmness and starch index levels for long-term and shorter-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.