MSU Extension

General comments

This is the fifth Michigan State University Extension apple maturity report from the Grand Rapids, Michigan, area fruit team. Unusually hot weather over the past week has not slowed apple harvest all that much, and with a lighter crop than average and adequate labor supply, farms seem to be keeping up just fine. The high temperatures did push apple maturity ahead of anticipated harvest dates a bit and some varieties are responding with lower fruit pressure and higher starch index levels.

The take-home message is to monitor your apple blocks closely to stay on top of maturity. The heat has made it very difficult to remove field heat prior to storage, which could lead to shorter storage windows than expected through the winter months. A more normal temperature pattern will fall in for a few days, but 80s are in the forecast again for next week, so color development will continue to be hampered I’m afraid.

Brown marmorated stink bugs seemed to be loving the very hot weather (or trying to find relief from it). There was a marked uptick in the presence of brown marmorated stink bugs in orchards, buildings and urban areas. This pest is a bit maddening in that we see the damage about the same time or even before we trap them. This means we don’t have a good way to monitor them yet.

With so many other hosts to feed on, it’s not surprising we can’t better understand when or why brown marmorated stink bugs move from crop to crop. I found six around my house this weekend without really looking for them—that’s more in three days than I found all of last year. They are building in population and creating more damage in crops, including apples.

Variety sampling results for the general Grand Rapids area

Gala harvest is winding down on the Ridge. Color on fruit left is excellent. Fruit firmness is still very good at 17.2 pounds. All fruits sampled had a starch index of 8—Galas not treated with AVG or 1-MCP are fast moving out of the best storage window even for short-term controlled atmosphere (CA). This will be the last week for Gala sampling in this report.

Of the few remaining Honeycrisp to sample, all maturity indices are indicating over mature fruits. Some blocks are waiting for more color, but with the very warm temperatures, it is unlikely you will get much additional color development and it’s best to just get them off the trees. Honeycrisp are likely to start getting that off-flavor if left hanging too much longer.

Firmness readings in Honeycrisp have dropped off from nearly 18 pounds of pressure for the last two weeks to under 16 pounds this week. Starch index for all fruits sampled were 8s. Brix level has changed little at 12.2 this week compared to 12.3 last week. This is likely to be the last week for Honeycrisp data in this report.

Empire continue to move very slowly moving forward in their maturity as is typical for this variety. They are still in a long-term C) window in the Grand Rapids area, but moving closer to the mid-term CA storage range.

Color is favorable at 67 percent. The background color is in the 1 to 4 range with 2.5 being the average. Fruit firmness is still very good at 17.7 pounds this week, down from last week’s 19.6 pounds. The starch index readings were similar to last week averaging 4.7. Brix are the same average at 13.4, but we do see a few more readings in the 14 and 15 brix level.

Empire are not a big variety for the Ridge overall and you should get them harvested as time allows, knowing that they are in the perfect stage for long-term CA right now and moving slowly in their maturity. Fruit drop could be a response to all the recent hot weather, so don’t wait too long on Empire.

Jonagold has moved very quickly through its maturity this year, a bit faster than normal. Internal ethylene production is about the same as last week with 40 percent of fruits reading over 0.2 ppm. Red color is also similar to last week at 38 percent. The background color ranges from 2 to 5 with an average of 3.8, a little higher than expected with the starch levels we are seeing this week.

Fruit firmness is still good to excellent at 17.1 pounds, and only down slightly from last week’s samples. Starch index readings averaged 7.1 compared to 6.7 last week. Brix level is up slightly from 13.1 last week to 13.3 this week.

We saw a small amount of water core in our samples this week, perhaps due to a lighter crop load. The predicted harvest date for Jonagold was Sept. 27 for peak harvest. Many Jonagold have come off in the past week for the processing market.

Golden Delicious have a predicted harvest date of Oct. 1 for the general Grand Rapids area, but they seem to be well ahead of that date in their maturity development. They are perfect for long-term CA storage this week and I see some have started to be harvested in recent days. I suspect by late next week, we will see samples of Goldens move into a mid- or short-term CA storage window, so best to get them in the bins soon.

We saw a bit of water core in a few Golden Delicious apples this week, which isn’t unheard of, but a bit unusual given the very dry weather of late. Perhaps it is due to a light crop load in our samples sites. Damage from brown marmorated stink bugs is all too apparent on Golden Delicious in some spots.

We sampled Red Delicious for the first time this week. The predicted harvest date for Red Delicious is Oct. 4, which looks to be right on target for the peak harvest potential. A few Red Delicious are being harvested already on early sites and in blocks with good color. They are just coming into their long-term CA storage window. If color is good and the workers are available, get started on Red Delicious. We did see a little water core in our initial samples, which is not unusual for Red Delicious and nothing to be concerned about yet.

Ida Red was sampled for the first time this week and seem to be a bit farther ahead than expected—very similar to last year when they fooled me by taking their time to move forward in maturity. Time will tell and our predicted date for peak Ida Red harvest is Oct. 9, which will most likely be close or maybe a few days on the too-late side. Firmness is excellent at 17.6 pounds. The starch readings caught us by surprise a bit with an average of 4. Starch readings were quite variable across samples ranging from 1 to 6. We will have better idea of what Ida Red is doing with next week’s samples.

Late-season Fuji strains appear to be right on target with a predicted harvest date of Oct. 24. While some of the maturity indices seem to be more advanced than you would expect, we often see this with Fuji, but then they take their time to move forward. We saw the same scenario the last several years in our sampling. One more week of sampling will give a better picture of how Fuji is moving. They are still immature at this time. Very little to no water core is being found Fuji.

Next week we will add several more varieties to our sampling for the late-season harvest period—Rome, Braeburn, Cameo, Evercrisp and others are on my wish list.

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