MSU Extension

General harvest comments

The recent heat wave has many growers struggling to keep up with a rapid advance in maturity in several varieties. Honeycrisp, Jonagold and several other cultivars are being picked in earnest in an effort to get to fruit before it becomes over-mature for long-term controlled atmosphere (CA) storage. Hot fruit going into storage continues to be a major concern. We encourage growers to read the article “Hot, hot apple harvest concerns” for a summary of steps that can be taken to alleviate some of the issues we expect in these conditions.

Warm fruit is going to continue to be a problem for at least another several days. While daytime highs are forecasted to drop into the low 70s, nights will be unseasonably warm. This will mean growers will not be able to rely on natural cooling of fruit left in bins outside overnight. This puts all the pressure to cool off fruit properly on man-made coolers, so proper handling and placement of the fruit at the storage facility is particularly crucial this season.

Brown marmorated stink bugs are still very low in the area. Areas further south have started to catch significant numbers in trap lines, but the trap line in west central Michigan is still not catching anything. The same is true for the team in northwest Michigan. This pattern has been fairly typical this season all over Michigan—they do not seem to be showing up in traps until very late. In spite of low trap counts, damage has increased in blocks down on the Ridge over the past couple of weeks, though little has been reported in this area. They are particularly common in other areas on Golden Delicious, so growers looking to keep an eye out for this pest should watch this cultivar closely until harvest has concluded.

Second generation of codling moth is over, and trap counts have dropped down to zero in most blocks. We are not expecting a third generation. Several growers have asked about whether there is a chance the recent heat wave could cause a third generation of codling moth. We believe that because the heat wave came after an extended period of cool weather and short days, the insect should stay in diapause. This means no third generation should be expected, and growers can assume no spray is necessary.

The normal and estimated 2017 peak harvest dates for apple varieties in Grand Rapids, Michigan, is included at the end of this report. While we have historically assumed that we lag behind the Ridge in the west central region, this does not seem to be so much the case this season in many areas. Data in the following tables are based on samples collected from commercial orchards in Oceana and Mason counties. Firmness and starch ranges are observed as low and high mean values. Optimum long term storage parameters are also included at the end of the article.

Individual variety results

Honeycrisp was sampled for the sixth time this week. Target starch index for this variety for long-term CA storage is 3.5, and Honeycrisp has surged past this mark to an average starch index of 7.54. Honeycrisp are considered over-mature for CA storage at a starch index of 7 and pressure for even short-term CA should be around 15 pounds. Fruit pressure has dropped over the past several days down to a regional average of 13.49, and fruits at some sites are starting to feel “waxy,” another telltale sign of over-maturity.

There is still a lot of Honeycrisp hanging in trees around the west central region, and fruits in most blocks need to come of the trees as quickly as possible at this point if they are intended for CA storage of any length. They are starting to eat overly sweet, and the characteristic crunchy texture of this variety is beginning to suffer as fruit become over-mature.

Color on Honeycrisp continues to be outstanding this season, and water core continues to be low. Bitter pit is common in sites bearing a light crop due to spring frost, but this disorder is not common in blocks bearing a full crop this.

Jonagold was sampled for the fifth time this week. The target starch index for long-term CA storage is 3.5, with ideal pressure of 15-17 pounds, depending on desired length of storage. Jonagold is considered over-ripe for CA storage at a starch index of 5.5, so based on the average starch index of 6.2 and pressure of 15.24, we are quickly exiting the optimal harvest window for this variety. Jonagolds are ready to be picked and should be prioritized this week before they become over-mature.

Jonathan was tested for the fourth and final time this week, and they are ready to go. Most Jonathan in the area have been harvested already. The starch index target for CA storage is 3.5, and Jonathan tested well above that mark this week. Firmness is also right in the ideal range for CA storage. Color on Jonathan is outstanding this year, but some red bleeding into the cortex was observed this week on the redder strains. Remaining Jonathan will probably be off of trees by the end of the week. They seem to be holding quality very well, showing little change from last week in development.

Empire was sampled for the fourth and final time this week. Most of the Empires in the area have been harvested already, and growers will be finished with this variety by the end of the week. Firmness fell toward the lower limit for ideal CA storage from last week and starch index shot up, indicating that the ideal window of harvest for this variety is coming to a close. Color, texture and flavor are outstanding on Empire this season, but size has been lacking at many sites.

Golden Delicious was sampled for the third time this week, and is ready to be harvested at the majority of sites in the region. Our predicted harvest date for this cultivar is not until Oct. 1, but many sites will be harvested well ahead of that mark this year. That said, this is a cultivar that growers who are feeling stressed for time can leave for a few more days without concern.

Firmness is holding nicely, brix barely moved from last week and the starch index of 4.08 is well below the over-mature CA storage mark of 6.5. Honeycrisp and Jonagold should be everyone’s top priority right now; the Goldens can stand to hang for a few more days. Red blushing continues to be evident in most blocks. Unfortunately, weather for coloring earlier this month was so good that a portion of most Golden Delicious fields have 5-10 percent red blush, so this may be an issue for growers and processors this year. There is not really anything that can be done about the blush except harvesting a hair earlier than usual to avoid any further color development.

Red Delicious was sampled for the second time this week. This variety still has at least at least a week to go before maturity at most locations. Red delicious is considered mature for CA storage at a starch index of 2.5, so we are not far off from early maturity. Color on Red Delicious is great this year. Picking based on appearance is not wise right now, as color is so rich that many blocks look ripe but are still testing very low on the starch index scale.

Ida Red was sampled for the second time this week. Harvest of this cultivar is about two weeks off at most locations. Fruit pressure really dropped with the heat this week which is a potential concern, so growers are hoping that the quality of fruit holds until starch and brix reach acceptable marks. Color on Ida Red is nice this year, most have at least 50 percent red blush.

Rome was sampled for the first time this week. Romes are considered mature for CA storage at a starch index of 3, and this week’s average was just below that mark. However, some sites are averaging slightly above three at this time, so early harvest of Rome has begun at some locations. More will continue to be harvested next week. Firmness is excellent in this variety right now. It does not seem to have been softened by the recent high temperatures like so many others varieties.

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