General apple harvest comments

The relatively warm conditions continues to push apple maturity quickly this year. The recent dry weather has generally cooperated with harvesting activity. Area growers are busy picking Gala and spot-picking Honeycrisp.

Please be aware that samples we collect for this report are from the central Berrien County region, targeting more mature fruit on the outside of the tree canopy. Fruit in the interior of the tree will be less advanced than shown here. Sites with heavier soils and greater crop loads will generally be less mature.

Brown marmorated stink bug is damaging fruit in some area orchards, especially orchard sides close to woods, soybean fields, ravines and where natural hosts such as buckthorn, tree of heaven and mulberry have served as food sources. Some gathering of stink bugs on sunny sides of buildings has begun, maybe triggered by cooler nights.

Oriental fruit moth, codling moth, obliquebanded leafroller, apple maggot and San Jose scale are additional pests of concern at this time of year. Sooty blotch and flyspeck diseases are favored by the warm, wet conditions we have had in recent days. A few apples, especially light colored varieties, are infected by the fungal disease bitter rot, which appears as circular, dark fruit spots with salmon-orange, slimy spores most visible under rainy conditions.

Individual variety results

Gala was sampled for the third week. Last week, starch readings for the past two weeks jumped from 1.5 to 3.3, to 5.4 for this week, so apple maturation has proceeded rapidly. All seven Gala sites tested this week had starch conversion of 4.4 or greater, well in the mature zone. Target starch index for maturity for this variety is 3.

Although the area average firmness was 20 pounds for this week, two of seven sites had fruit firmness at or below the minimum firmness of 18 pounds recommended for long-term controlled atmosphere (CA) storage. Predicted peak harvest date for central Berrien County is Sept. 10.

Honeycrisp was sampled for the third week and is showing rapid maturation. Starch conversion moved from an average of 2.9 last week to 5.3 for this week, all sites testing above the target mature starch index of 3.5 for this variety. The predicted peak harvest date is Sept. 18 for central Berrien County, so this variety is maturing ahead of the predicted date.

Fruit firmness is averaging 15.9 pounds this week, almost 2 pounds less than last week, with the general guideline of 17 pounds for best long-term CA storage and 16 for mid-term storage.

Jonathan was not sampled because most area blocks have been picked for taffy apples.

Jonagold was sampled for the first time this season. Starch conversion is averaging 2.3 this week, with 3.5 as the target for mature for this variety. The predicted peak harvest date is Sept. 24 for central Berrien County, which seems to indicate this variety is maturing slightly ahead of prediction. Brix for this week is 11.4.

Fruit firmness averaged 19.5 pounds this week, with the general guideline of 17 pounds for best long-term CA storage. Watch this variety closely as both the firmness and internal starch conversion seems to be moving rapidly toward maturity.

Empire was sampled for the first time this season. Starch conversion is averaging 2.1 this week, with 3.5 as the target for mature for this variety. The predicted peak harvest date is Sept. 23 for central Berrien County. Brix for this week is 11.4.

Fruit firmness averaged 18.5 pounds this week, with the general guideline of 16 pounds for best long-term CA storage. Based on these tests, harvest for fresh market can be delayed to wait for better size and quality.

Golden Delicious was sampled for the first time this season. Starch conversion is averaging 1.5 this week, with 3 as the target for mature for this variety. The predicted peak harvest date is Sept. 27 for central Berrien County.

Brix for this week is 11.4. Fruit firmness averaged 18.2 pounds this week, with the general guideline of 17 pounds for best long-term CA storage. One site is already testing below the 17 pound threshold. As seems to be the case this year, watch this variety carefully as apples seem to be ripening before the predicted harvest date.

Early Fuji is testing well in the mature zone. Starch conversion is averaging 4.9 this week, with 3 as the target for mature for this variety. The predicted peak harvest date is Sept. 1 for central Berrien County.

Brix for this week is 13.3. Fruit firmness averaged 17 pounds this week, with the general guideline of 18 pounds for best long-term CA storage, although this variety is generally used for direct fresh sales rather than long term storage.

For additional comments from Randy Beaudry, MSU Department of Horticulture, read his general observations from MSU Apple Maturity Lab for 2018.

*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.