MSU Extension

General harvest comments

Unseasonably warm weather in late September and early October has continued to move apple harvest along at an accelerated pace. Most growers will be finished with everything except late seconds, juice picks and a couple of late-season small acreage varieties like Fuji and Evercrisp by early next week. We can expect the weather to begin to cool off in the next several days.

More late-season fruit drop has been observed in the past week. This is a common tree stress response late in the season under hot, dry conditions. We have had very little rain in the past several weeks, and trees bearing a heavy crop are under a lot of environmental stress. Trees will drop fruits in response to these conditions. Drop is particularly noticeable in any block where PGRs such as ReTain were not used.

Brown marmorated stink bugs are still very low in the area. Areas further south have caught 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 the northwest part of the state. This pattern has been fairly typical this season all over Michigan—they do not seem to be showing up in traps until late in the season, probably sometime after they start being attracted to apple fruits.

We have seen a little bit of spotty damage from brown marmorated stink bugs on Golden Delicious and Jonagold in the past several days here in west central Michigan. While not common, there have been a couple of smaller blocks with some significant damage. While Jonagold harvest has largely concluded at this time, growers with late Golden Delicious picks should keep an eye out for signs of damage until harvest has concluded. Blocks with some damage this year are the first place to start for those considering late-season management sprays next year.

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. Since 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 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 we lag behind the Ridge in the west central region, this has not been the case this season. 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

Jonagold was sampled for the sixth and final time this week. The target starch index for long-term controlled atmosphere (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 6.4 and pressure of 14.25, we are now past the optimal harvest window for this variety. What few Jonagold that remain need to be harvested as soon as possible, particularly if they are intended for CA storage of any length. They are eating overly soft and sweet at this point.

Golden Delicious was sampled for the fourth and final time this week. The Golden Delicious that remain on trees in the area are ready for harvest and will mostly be finished by the end of the week. Golden Delicious are considered over-mature for CA storage at a starch index of 6.5, so we are rapidly exiting the optimal window for harvest on this variety. We can also see firmness really dropped and brix ticked up nicely in the past seven days. Most Golden Delicious fields have 5-10 percent red blush, so this may be an issue for processors this year. For those selling to fresh market venues however, a little pink blush can be a desirable trait.

Red Delicious was sampled for the third time this week. It has reached very early maturity for CA storage at a couple sites, but the regional average is still just below the early end of long-term CA storage maturity. Red Delicious is considered mature for CA storage at a starch index of 2.5. This variety barely moved between this week and last week, and firmness is still holding nicely. As a result, Red Delicious could stand to sit on trees for at least another five to seven days at most locations, particularly for growers who are feeling stressed for time as they get other varieties cleaned up.

Ida Red was sampled for the third time this week. This variety took a huge leap forward in maturity over the past seven days and is now ready for harvest for growers who are looking to put it into CA storage. Ida Red is considered ready for CA storage at a starch index of 3.5 and ideal firmness of 14-16 pounds, so we are there (and already below ideal ranges for fruit firmness). Fruit firmness may be a concern on this variety this year, as the recent heat seems to have really softened it up.

Rome was sampled for the second time this week. Rome is considered mature for CA storage at a starch index of 3, and we have just crossed over that mark. Firmness continues to be excellent in the variety—it has not been affected by the late-season heat weave like so many others. Very little red bleeding has been observed in Rome this season.

Winesap was sampled for the first time this season. It still has a long way to go, fruits are firm and starchy right now. Size and color are both good on the variety.

Evercrisp was tested for the second time this week. Although this variety represents a very small amount of acreage in west central Michigan, it is gaining interest across the state as growers consider late-season fresh market apple planting options going forward. Trees are still very young, so the reliability of maturity results is a bit of a toss-up. However, we have begun testing it to gain some new insights on the variety going forward. This variety is already distinguishing itself as being exceptionally firm and sweet. The firmness of the variety is particularly impressive this season given how hot it has been—many other varieties have struggled with fruit firmness, but this variety has not had these issues.

Fuji was sampled for the first time this season. Fuji is considered mature for CA storage at a starch index of three, with ideal firmness of 16-18 pounds depending on desired length of storage. It is considered over-mature at a starch index of 7. This week’s results indicate Fujis are in the early range of maturity for CA storage in west central Michigan. However, they can stand to wait at least another week as growers finish up other varieties. We typically expect Fuji to be a much later October harvest, but like so many other varieties this season, it will likely be picked one to two weeks ahead of normal this season.

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