MSU Extension Apples

General comments

There are very few blocks with apples remaining to be picked in the general Grand Rapids, Michigan, area—we are quickly nearing the end of the 2020 harvest season. Many growers tell us they will be done early next week for even the latest varieties. Apple maturity continues to run close to or slightly ahead of our 2020 predicted apple harvest dates.

On our Michigan State University apple maturity team call this morning, all members reported that farm markets continue to host record-breaking crowds in 2020 with a strong uptick in the desire for U-pick apples and an outdoor adventure. Fresh retail sales have been very good as well—higher than expected.

This will be a big week to finish up Fuji harvest. The very late season varieties such as Evercrisp, Pink Lady and Braeburn will likely finish up in the next week or two if we don’t experience too many rainy days. The forecasts show chances for rain nearly every day over the next 10 days, but it looks to be variable showers so harvest should be able to continue. There have been more frosty nights than in the past few years, but fruit seem to be holding well and, in some cases, are hard to remove (most likely due to ReTain or Harvista use).

If you find you have a break in your harvest schedule while waiting for late varieties to ripen, this is a good time to work on fall orchard clean up (mowing, trellis repair, etc.). In blocks were harvest is complete, you could get started with post-harvest nutritional sprays or some fall herbicide needs. If you have nursery trees to dig, you could get started on that as well. It is preferred that leaves are mostly dropped to avoid issues with rot and mold during storage. There are some applications that can be made to help with defoliation. Let me or your spray rep know if you need some guidance (irisha@msu.edu).

Variety sampling results

Strains are noted where applicable. We try our best to collect samples from blocks untreated with harvest management products, but I do make note of samples that had ReTain applied if we know of it.

Our Rome sample this week shows a clear movement forward in maturity. I did find out that the trees I was sampling from had been treated with ReTain, which explains the slight delay in maturity from our predicted harvest date of Oct. 16. It might also explain why there is no bleeding in these very red Romes. Color, firmness and brix are all now in the range for harvest and long-term controlled atmosphere (CA) storage needs. There was no water core in our Rome samples.

Our Fuji sample shows some maturity movement from last week. This variety always seems to jump out of the maturity gate early, but then takes it time to get to the right levels for long-term CA storage. Many Fuji blocks are being cleaned up this week. Red color is outstanding this year in Fuji and even managed to improve a bit more this week. Background color is about the same. Starch clearing made the biggest leap forward from 3 last week to 5.3 this week.

Watercore is quite prevalent this year in many Fuji blocks. Nine out of 10 apples in our sample had water ore at some level. I haven’t looked yet, but the internal callus tissue around the seeds is likely to be present this year with the high sugar levels in Fuji. This sometimes gets kicked back from uninformed buyers as mold. Mold would be soft and pliable with a stringy nature. The callus tissue is hard and firmly a part of the seed capsule.

Evercrisp, like Fuji, seems to be ahead of the normal late October predicted harvest timing. Just like Fuji, red color is very high in Evercrisp this year. They still have that ruddy brownish-green background color, but that is fading and much less prominent than in past years. The maturity readings this week are only slightly changed from last week. It is likely Evercrisp will be ready after Fuji, but you can harvest them when you are satisfied with the color, particularly when that brownish color fades. All our experience with Evercrisp so far indicates it is very prone to watercore. Ten out of 10 apples in our samples had watercore at some level.

The internal ethylene in Granny Smith started to increase significantly this week with 50% of fruits now over the 0.2 ppm climacteric. Cool nights have produced a very prominent red blush on Granny Smith this year—they are pretty. This variety likely needs at least seven to 10 days before it moves into a more eatable state—two to three weeks would be even better. Watercore is an issue in Grannies with five out of 10 apples showing it at some level.

We sampled Pink Lady for the first time. The strain is Barnsby, which we do not have maturity guidelines for in Michigan yet. They do have some internal ethylene production with 40% of fruits over 0.2 ppm. Red color is very good this year. They probably need at least a week or two to improve in maturity for better eating. There was no watercore in the Pink Lady.

Many changes in apple physiology occur over time as fruit become more mature—starch is converted to sugar; seeds turn a darker color; acidity decreases; chlorophyll levels decrease; respiration increases; cell walls weaken, fruit begins to soften; and ethylene production increases. Our MSU Ridge Apple Quality Lab and the MSU campus Beaudry Lab measure these and many other factors to help you make harvest management decisions:

Apple maturity sampling parameters

• % fruits with internal ethylene over 0.2 ppm = indicates when ethylene begins to influence fruit ripening and it cannot be held back easily after this is reached.
• Color % = the visual percentage of red color from 0 to 100; range is of all fruits tested
• Background color: 5 = Green, 1 = Yellow; range is of all fruits tested.
• Firmness in pounds pressure
• Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
• Brix = % sugar

We are graciously funded by the Michigan Tree Fruit Commission, Michigan Apple Committee, Michigan State Horticultural Society and Michigan State University Extension. Many thanks to all the growers and industry representatives that donate to our program.

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