MSU Extension

General comments

This is the sixth Michigan State University Extension apple maturity report from the Grand Rapids, Michigan, area fruit team.

The very hot temperatures seemed to have moved all the later season varieties forward in their maturity. Starch Index has been pushed forward quicker than expected. Keep an eye on later varieties to make sure they don’t move faster than expected.

Variety sampling results for the general Grand Rapids area

Quite a number of Jonagold were harvested in the last week, which is a good thing. This variety moved very quickly through the maturity indices and any fruit left hanging and not treated with AVG or 1-MCP should be moved through fresh sales channels.

Golden Delicious had a predicted harvest date of Oct. 1 for the general Grand Rapids area, and many were harvested in the last week. The block we sample from were harvested, so no additional data this week. Golden Delicious will quickly move out of the perfect stage for long-term controlled atmosphere (CA) storage and by the end of this week they will be in a mid- or short-term CA storage window.

Our second week of Red Delicious sampling show they are ready and still in condition for long-term CA storage. The predicted harvest date for Red Delicious is Oct. 4, which looks to be right on target for the peak harvest potential. We see an increase in internal ethylene production form last week. Red color is greatly improved from 71 percent on average last week to over 91 percent this week. Background color is more yellow than last week with readings of 1s and 2s. Starch is still variable for individual apples ranging from 1 to 7 with an average of 2.9 this week compared to last week’s 3.4. Brix are very good at 14, up from last week’s 12.4. Get Red Delicious harvested as time and talent allows.

Our predicted harvest date for Ida Red is Oct. 9, which seems to be a little on the late side when looking at the data from the last two weeks. Firmness is very good at 15.7 pounds, down from last week’s 17.6 pounds. The starch readings are 2.9 on average compared to 4 last week, so they seem to be moving through their maturity rather quickly. Ida Red are now in the long-term CA storage window and will likely move quickly out of best condition for long to mid-term CA storage, so get them picked as soon as you can.

Cameo is not a common variety overall, but we see more planted each year. Our sampling this week shows 20 percent of fruits with internal ethylene over the 0.2 ppm climacteric. With a background color averaging 2.7 and starch readings averaging 5.3, Cameo is near the optimum harvest window for long-term CA storage.

Another newer variety is Crimson Crisp and it was sampled for the first time this week. Fruits have a high percentage (90) over the 0.2 ppm climacteric, which will enhance the ripening process. The red color on this variety is very nice averaging 87 percent. The background color is on the low side at 1.5, which indicated mature fruit. Fruit firmness is excellent at 21.1 pounds on average. Starch Index readings are quite high at 7.3, also indicating mature fruit. Brix readings are very good to excellent at 14.6. Crimson Crisp should be harvested soon for even mid to short-term CA storage. They are just coming into an excellent range for fresh sales right now and eat pretty well.

Last week, I wrote that late season Fuji strains appear to be right on target with a predicted harvest date of Oct. 24. After a week of temperatures in the upper 80s and low 90s, it looks like Fuji have advanced rather quickly through their maturity and you will want to keep a close eye on your blocks in the next week to 10 days and perhaps begin some early harvest for long-term CA if fruits are not treated with harvest management materials. Very little to no water core is being found Fuji at this time. All maturity indices listed below show a rather big jump forward for Fuji and harvest could begin 10 days or so from now.

Kanzi is another new apple variety and we don’t know that much about its maturity profile. From the fruits tested this week, it seems very similar to late Fuji in its development and will probably be harvested at that timing.

Another variety that is ahead in its maturity development is Rome. Our sample is from Law Rome. Very few fruits have internal ethylene over the 0.2 ppm climacteric. Red color is good, but should improve. The background color is 3.2 indicating immaturity, but not as green as expected. Firmness is excellent as is expected with Rome at 23.2 pounds. Starch, like background color, is lower than expected. Brix readings are rather good for Rome at 13.3. Our predicted harvest date for Rome is Oct. 14, which might end up being a little late after the warm weather pushed fruits ahead quickly. There has been very little bleeding in Rome so far.

Evercrisp is another newer variety that we don’t yet have a full picture of its maturity profile or a good idea of a predicted harvest date. Surprisingly, the internal ethylene readings show all fruits over the 0.2 ppm climacteric. We saw similar data in 2016. Red color is poor at 42 percent. Background color is averaging 3.9. Firmness is very excellent at 23.3, as are brix at 16.5. Starch index readings were in the 2 to 5 range with an average of 3.3. I didn’t get a chance to taste the Evercrisp this week, but I imagine they still eat rather starchy, but could change quite a bit in the next week or so. Keep an eye on your blocks.

We added Pink Lady to our sampling this week. We are looking at Maslin, which is earlier to mature than standard Pink Lady. Internal ethylene was a bit surprising with 80 percent of fruits being over the climacteric. Red color is quite variable ranging from 15 to 90 percent and should improve in the next two weeks. Background color is still green at 4 for an average. Firmness is very good at 19.8 pounds. Starch readings range from 1 to 7 with an average of 3.6. Brix are already excellent at 15.6. Pink Lady is still immature according to the numbers and most likely will need another week or two to improve.

Braeburn has a predicted harvest date of Oct. 24 and most maturity testing indicates immature fruits. The exception is the starch index, which ranges from 1 to 4 and averages 2—a bit surprising for Braeburn this early. Red color and brix need some time to improve.

Granny Smith should have a harvest date similar to Braeburn and the maturity indices show immature fruit, with the exception again of the starch index being lower than expected.

We will continue sampling apple varieties for at least another two weeks or as fruits are available.

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