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

Gala and Honeycrisp harvests are winding down. Cooler weather has helped to keep fruit firm and improve red skin color of Honeycrisp and Jonagold. Some Golden Delicious and early strain Red Delicious have been harvested.

Growers are noticing blister spot symptoms, caused by the bacterial pathogen Pseudomonas papulans on Crispin (Mutsu) and to a less extent on Fuji and Pinova. Infection occurred much earlier.

The Trevor Nichols Research Center (TNRC) reports an upsurge in apple maggot trap catches over the past two weeks. Normally we see a decrease in catches by early September. Some years, growers have reported problems due to apple maggots in mid-September.

Based on a codling moth model developed at MSU, 2014 has been too cool for the second generation to develop into moths, thus no third generation larvae are expected and the potential for late-season fruit damage has decreased. In hot years such as 2005, a third generation will develop and cause fruit damage in September.

Oriental fruit moths continue to be a threat in September. Moth catches at TNRC and trap lines maintained by Crop Protection Services has remained high in some orchards over the past four weeks. In recent years, this insect has become more common in apple orchards, even those with no peach orchards nearby.

Specific apple variety comments

Gala harvest is in its third week in southwest Michigan. Some growers are reporting that Gala fruit are requiring more force than usual this year to pick. Spurs are coming off with the stems, even though they tested mature and no stop-drop spray was applied. Fruit waxiness is starting to become noticeable in a few blocks. Firmness average is 18.4 pounds this week, down about 1 pound from last week. Starch conversion average jumped from 4.8 last week to 6.8 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. Eating quality is good.

Gala 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, about the same as last week and close to the recommended firmness of 16 pounds for mid-term CA storage. Starch conversion is averaging 6.1, above the target of 3.5 needed for good flavor. Some drop has been noted, in part due to the winds of last Saturday, Sept. 20.

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 17.1 pounds, the same as the recommended minimum firmness of 17 pounds for long-term CA storage. Fruit in general have sufficient internal maturity for harvest as indicated by this week’s average starch index of 5.0, above the 3.5 minimum recommended for long-term CA storage. Red skin color is excellent on newer strains such as Rubinstar, but still significantly green background color on older strains such DeCoster may influence growers to delay harvest for these. 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. Target starch index for Jonagold is 3.5.

Jonathan samples (five locations) are testing 16.9 pounds; the ideal minimum firmness for good long-term CA storage is 16 pounds. The continued good firmness in some blocks allows harvest to be delayed to wait for bigger size and more sugar. Starch indices are averaging 3.9, slightly better than the minimum 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.

Golden Delicious orchards in central Berrien County are testing an average of 18.8 pounds of firmness with an average starch index of 2.2, a slight improvement over starch readings of 1 to 1.8 for last week. Minimum recommended firmness for long-term CA is 17 pounds, with a starch reading of 3 or more considered mature. Pink blush is noticeable in some blocks this year. Background color is still generally green. Some blocks have been harvested for apple pie slices.

Golden Delicious maturity summary

The predicted long-term storage harvest date for Golden Delicious in 2014 at SWMREC is Oct. 3. Target starch index for Golden Delicious is 3.

Red Delicious early strains such as Earlichief and Schlect have been picked in some orchards. Red skin coloration has intensified in many blocks with background still showing green highlights. Some fruit are showing red in the vascular bundles in the flesh at the edge of the core. Fruit picked Monday this week, Sept. 22, are averaging 19 pounds of firmness, slightly more than the 18 pounds of minimum recommended firmness for fruit destined for long-term CA. Starch conversion index averaged 1.9, below the target of 2.5 for long-term CA.

Red Delicious maturity summary

The predicted long-term storage harvest date for Red Delicious in 2014 for central Berrien County is Oct. 7. Target starch index for Red Delicious is 2.5.

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-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.