MSU Extension

This is the first of weekly apple maturity reports for southwest Michigan from early September until mid-October 2015. The samples for these reports are collected primarily in Berrien and Van Buren counties – the maturity is only a broad indication of trends for this area.  Sites north of here, closer to Lake Michigan, on heavier soils, or with heavier crop loads will generally harvest later.

Contact Bill Shane at the Southwest Michigan Research and Extension Center (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 Michigan State University Extension Apple maturity program and reports page by Wednesday afternoon each week.

General comments

The 2014-2015 winter was again long and cold with a late cool spring that eventually became somewhat normal in May and June. Little to no frost events occurred. Precipitation across the area has been quite variable this year with Hartford, Lawrence and Keeler weather stations totaling 20 to 21 inches from April 1 to the end of August and Hartford at 13.6 inches and the rest in the 18 to 19 inches range. Sites with higher rainfall will tend to have bigger fruit size.

The Michigan State University Extension predicted harvest dates for every Enviro-weather weather station (previously known as MAWN stations) is now available on the Michigan State University Enviro-weather website. In general, the 2015 predicted harvest dates are roughly a week behind normal and approximately the same as last year. Bloom dates this spring were also behind normal across the state.

General comments for this week

Marmorated stink bug reports are few again this year, so far.  The highest catch so far has been in the Stevensville area in a non-agricultural site.

Empires and Jonathans are being picked for taffy apples.  Gala harvest is underway for some of the earlier maturing sites in the area.  Some spot picking of Honeycrisp is expected to begin by the end of this week for a few sites in the sandier areas of Berrien County.

Detailed tests for this week – see suggested firmness and starch levels for harvest in Table 1

Gala comments: Skin color development on the newer red strain Gala is good. Galas taste starchy, in line with the low average starch removal index of 2.5. Target starch index is 3. The predicted long term storage harvest date for 2015 for SWMREC is Sept. 7.  The long-term normal harvest date for Gala in Berrien County is Sept. 8. One site out of 5 tested this week tested above the target index of 3 for start. Firmness is 21 lb or higher. Excellent firmness will allow harvest to be delayed to wait for better size, color and flavor. See comments below about Gala.

Mac comments: The predicted long-term storage harvest date for main season Macs in 2015 for SWMREC is Sept. 6. Target starch index for Macs is 5.  Background color is still relatively green.

Honeycrisp comments: The predicted long term storage harvest date for Honeycrisp 2015 for the central Berrien County area is Sept. 9. Target starch index for Honeycrisp is 3.5. Background color for standard Honeycrisp strains are generally green. Two of the three sites tested were close to the target starch index for maturity with firmness down to the 16 to 17 lb range already. Spot picking is justified in some of the earlier sites. Some sunburn symptoms are being seen on exposed fruit.

*Firmness is measured with a mechanical 11-mm wide probe inserted into the pared flesh of a fruit to a distance of 8 mm. 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.)

Highlight – Gala Maturity (thanks to Randy Beaudry, MSU Horticulture)

MSU guidelines for Gala apple maturity recommends a starch index of 3. Actually, Gala fruit with a starch index of at least 2 can be harvested for long-term storage without negative consequences. In fact, the fruit should store exceptionally well if placed in controlled atmosphere storage (CA) or treated with 1-MCP at this stage of development. Gala are a robust fruit without undue sensitivity to disorders like superficial scald, so an early harvest does not compromise storage quality. We wouldn't for instance, make the same early harvest recommendation for Cortland, which is extremely sensitive to superficial scald.

The Brix (percent sugars) in Gala with starch index of 2 will generally be low, but as the starch converts to sugars in storage, they should reach an adequate sugar level for the variety.  However, if the fruit will be harvested and sold, and consumed quickly, Gala harvest should be delayed to allow fruit to mature to better eating quality. Galas with a low starch index straight from the tree will taste starchy.  

A reason for early Gala harvest is that these fruit will store well in a year in which there is a very large crop nationally, allowing us to hold on to the fruit as long as is needed to market them. Early harvest can be helpful for labor management, extending the overall harvest window. Gala fruit left on the tree will still grow in size--so an early harvest will reduce yields slightly. However, if the fruit are large, then an early harvest is advisable since larger fruit have the potential to soften more rapidly and extensively than modest-sized fruit.

Looking for more? View Michigan State University Extension’s Apple Maturity Program and Reports resource page for regional reports throughout the state and additional resources.