MSU Extension Apples

General comments

Heavy rainfall slowed harvest last week with some areas around Grand Rapids, Michigan, receiving over 4 inches of rain. This week will be a big week for putting Gala and Honeycrisp in the bins. In general, internal ethylene levels continue to be on the low side for many varieties, apart from Honeycrisp with is a high ethylene producing variety. Fruit firmness continues to be on the higher side of normal still. Fruit color is outstanding. In general, disorders such as bitter pit and water core have been not as prevalent this season.

Brown marmorated stink bug and other stink bugs have shown an uptick in activity in and around apple orchards. Numbers have made a 10-fold jump in some known hot spots, so don’t let your guard down for this late season pest. Scout borders, especially near wooded areas, with lured traps. Orchards near soybean fields can sometimes be at a higher risk as beans begin to dry down and brown marmorated stink bugs move out to look for other food sources.

The rather moist conditions of late will get fungi active again in orchards. With the very heavy rain, the risk is not in stretching a fungicide spray, it’s that there is no fungicide left. Apple scab is still very much present and fruits will become susceptible as they near maturity, leading to pinpoint scab. The only way to prevent scab now is to make a fungicide application to prevent it from getting established on fruits. I like surprises, but not when it’s pinpoint scab on fruit when you open a room in January.

The abundant rainfall could get the summer diseases of sooty blotch and fly speck going again, as well as increase the risk for fruit rots. A good preharvest fungicide application can take care of a lot of future problems.

In the Grand Rapids area, apple maturity seems to be running close to our 2019 predicted apple harvest dates. We are seeing trends in maturity parameters that many varieties are ready about three or four days ahead of our predicted dates. Keep in mind these predicted dates are for peak harvest, so some fruits might be ready ahead or behind these dates as we move through maturity.

Variety sampling results

Strains are noted where applicable. We try our best to collect samples from blocks untreated with harvest management products. Samples collected for this report are from the general Grand Rapids area, targeting fruit that seems mature and on the outside of the tree and ready for the next picking.

My colleagues create a summary table for their reports, so I am peer-pressured to add the same. The individual variety results are found, with discussion, below this table.

Individual variety results

Gala

This will be a big week for Gala harvest in the Grand Rapids area. Many blocks have great color and can be stripped in one picking. Size is also good to excellent. The predicted harvest date for Gala was Sept. 15 and many blocks have fruits at the perfect stage for long-term controlled atmosphere (CA) storage right now—at least 18 pounds pressure and starch index of 3. Internal ethylene made a big jump in the last week with 85% of fruits over the 0.2 ppm climacteric, which will only increase with the hotter weather this week. Our samples this week are from traditional Gala, Gale Gala and Buckeye Gala, all data are lumped together.

McIntosh

McIntosh seem to be maturing slowly as usual and they are now in the window for long-term CA storage. The predicted harvest date of Sept. 20 is a few days off, but check your blocks and harvest as you can between Gala and Honeycrisp. Even though internal ethylene is quite low, fruit drop could become an issue quickly with the warmer than normal temperatures this week. Keep a close eye on Macs.

Early Fuji

Early Fuji blocks are being harvested as time allows. They are moving quickly out condition for any long-term storage, but perfect right now for direct fresh sales as they are typically marketed in.

Honeycrisp

Traditional Honeycrisp are starting to be harvested where color is ideal. There was some drop reported in early strains, so watch your blocks closely. Our predicted date for traditional Honeycrisp is Sept. 23 for peak harvest and this variety seems to be maturing ahead of that date. Firmness is excellent at 18.4 pounds on average. The starch levels have moved from an average of 5 to an average of 6.9 with a tighter range of starch levels from 3 to 8 compared to the wide range of last week from 1 to 8. Bitter pit is lower than expected this year for Honeycrisp even in blocks with large fruit size. This variety does what it wants to with no regard for normal.

Empire

Our predicted harvest date for Empire is Sept. 30, which seems to be a pretty good target; perhaps they will come in a bit ahead of that date for long-term CA. Internal ethylene is non-existent in Empire—that is typical of this variety. Fruit pressure is still excellent but has declined from last week. Starch levels are mostly in the 2 to 3 range, improved from last week when they were all 1 and 2. Brix is very good at 11.8. The target starch test for mature Empire for fresh market sales or fresh slices is 3.5 with a minimum firmness of 18 for long-term CA storage. Empire will improve greatly by next week and will be ready for long-term CA in about a week or so, but you could start to think about harvest if color and market is right.

Jonathan and Jonagold

We tested Jonathan and Jonagold for the second week. Fruits are still immature at this time but have definitely moved forward in maturity, particularly in the starch reading. The predicted harvest date for Jonathan and Jonagold is Oct. 6. Another week of testing will tell us more, but Oct. 6 might be a few days late, so we need to watch the maturity values carefully. I’ve separated out the data for all samples in the tables below.

Golden Delicious

The predicted harvest date for Grand Rapids area Golden Delicious is Oct. 8. Our second week of sampling indicates immature fruit, but with changes happening. Internal ethylene is still very low. Background color is unchanged at a level of 3. Fruit firmness is down from last week, averaging 16.5 pounds. Long-term CA likes a pressure no less than 17 pounds firmness—I suspect the heavy rains have something to do with the big drop and it should level out for next week. There is change in the starch conversion numbers with an average of 3.1 compared to last week of all 1s. Brix levels are improved from 11.5 last week to 12.7 this week. Goldens need a little more time, but they might end up being ready a few days ahead of the Oct. 8 date.

Nova Spy

Nova Spy is not a common variety. Our sampling this week show fruit changing in maturity only slightly. They probably need a week or more to improve.

Red Cort

Red Cort was tested for the second week and all fruits are still immature with only slight gains in maturity readings.

Red Delicious

This is our first week to look at Red Delicious. Fruits are immature at this time as expected with a predicted harvest date of Oct. 11. The background numbers seem unusually low (yellow) to me and I will check with the lab on it.

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 = measured with a Güss Fruit Texture Analyzer; range is of all fruits tested.
• Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.
• Brix = % sugar measured with Atago PAL-1 Pocket Refractometer