MSU Extension Apples

General comments

Continued rain is certainly helping with fruit size, but it does hamper harvest. Most growers are keeping up with harvest as best they can, and the general Grand Rapids, Michigan, area is over the halfway point for the 2019 season. When you are feeling overwhelmed, use knowledge to help you with important harvest decisions—work with your field help, crop consultants, storage operator and marketer to prioritize harvesting higher return blocks over low return ones.

Most Gala and Honeycrisp blocks are harvested. McIntosh are also done. Quite a few Jonathan and Jonagold blocks are being stripped this week. In general, internal ethylene levels continue to be on the low side for many varieties and starch clearing is running on the high side. Most varieties in the Grand Rapids area continue to mature about four to five days sooner than our 2019 predicted apple harvest dates.

Continued heavy rainfall will keep fungi active in orchards, fruit rots in particular. While the rots are different, they fall into two categories: those that enter apple tissue only through bruises, punctures and other wounds (blue mold, gray mold and mucor rot), and those capable of invading undamaged apples (white rot, black rot and bitter rot). The risk for fruit rots, bitter rot in particular, is very much increased with the heavy rains this fall. Bitter rot risk really depends on rain in the month before harvest; 2 inches of rain will remove storage rot fungicide protection and we have certainly had more than that in the last month.

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. The abundant rainfall could increase pressure for the summer diseases of sooty blotch and fly speck.

A good preharvest fungicide application can take care of a lot of future problems. It might even help with some late season russet by controlling yeasts on the fruit surface that can lead to russet.

Brown marmorated stink bugs continue to be active with numbers in traps declining over the past week. Very little damage has been reported in apples, other than in the areas with known high pressure over the past few years. 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.

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.

Individual variety results

Gala

Most Gala blocks have now been harvested. Those left are likely treated with harvest management products (i.e., ReTain, Harvista). Untreated Gala are quickly moving into the short-term controlled atmosphere (CA) storage window or for fresh sales.

Honeycrisp

Harvest is winding up. All fruit tested this week are 8s on the starch iodine chart. Fruit firmness is still very good at 16.3 pounds even with the heavy rainfall, which often softens fruit. Some second pick and very green interior fruits might need time to mature for long-term storage, but most blocks are being stripped this year in one picking where color is good.

Empire

Our predicted harvest date for Empire was Sept. 30, which was on target with harvest in the Grand Rapids area. Many Empire have come off as time allowed in the past week. Some treated with ReTain are still hanging and fruit quality is right there for long-term CA storage for fruits tested this week, which are most likely treated with ReTain.

Jonagold

Quite a few Jonagold have been stripped in the past few days. Our sampling block indicates Jonagold is moving out of that prime condition for long-term CA and is in the mid-term range. The predicted harvest date for Jonagold is Oct. 6, which seems to be about four to six days too late. Keep a close eye on your Jonagold blocks and harvest at the time that best fits your market for this variety.

Golden Delicious

The predicted harvest date for Golden Delicious in the Grand Rapids area is Oct. 8 and like Jonagold, this date might be five or more days too late for long-term CA storage. In general, Golden Delicious have a lighter than average crop load which might be moving the maturity faster than predicted. This week’s Golden Delicious samples show 0% of fruits with internal ethylene now over the 0.2 ppm level. Fruit firmness is only slightly lower than last week. Starch clearing is very similar to last week and Brix continue to improve.

Keep a close eye on Golden Delicious, especially fruit pressure and starch levels. This variety is behaving strangely this season and could move through maturity quickly. Some harvest of Goldens is starting in the Grand Rapids area as time allows. Many are reporting high levels of lenticel russet or whole surface rusting in Goldens. It was also more prevalent in Ruby Macs this season. Perhaps this is due to the heavy rains and high humidity levels and surface yeasts penetrating the surface.

Red Delicious

Red Delicious have moved forward very little over last week. Our predicted harvest date is Oct. 11, which will likely be a good target date with some harvest starting four or five days ahead of that date. Internal ethylene numbers are still very low with no fruits over the 0.2 ppm climacteric. Red Delicious is a very low ethylene producing variety. Red color is improved from 86% color to 90% this week. Fruit firmness is still very good at 20.3 pounds on average. Starch clearing is very similar to last week on average, but there were a few more fruits with readings of 3s and 4s where there were almost none the previous week. Red Delicious move very slowly through maturity, but will likely be ready for some long-term CA harvest in a week if not sooner.

Thinking back to the very wet weather in May 2019, I have to wonder if moldy core will be more of an issue in Red Delicious this year. I haven’t seen or heard of any yet, but do keep an eye on it.

Ida Red

This is the second week for Ida Red samples. Our predicted harvest date is Oct. 15. These early results indicate immature fruits with numbers oddly less mature than last week in many parameters. I am hearing of some Ida Reds being harvested in southwest Michigan, which is quite surprising. They need at least another week of testing here in the Grand Rapids area to learn more.

Rome

This second week of sampling Rome tells me they are moving steadily through their maturity, but not yet in prime condition. We are using Law Rome in our sampling. Our predicted harvest date is Oct. 20, which will likely be on the too-late side. We haven’t seen any bleeding yet but keep an eye on it and harvest ahead of the bleeding if possible to satisfy market demands.

Fuji

We looked at two different Fuji blocks this week for our first sampling of this late variety. Our predicted harvest date for late season Fuji is Oct. 28, which I am pretty sure no one will want to wait for and probably won’t have to. This first sample indicates Fuji is maturing faster than predicted harvest dates are forecasting. Fuji does tend to jump out of the gate a bit and then just sit there for several weeks with only slight improvements in color and starch clearing.

Keep in mind that Fuji often stains oddly for the starch index test and it will look farther along than it is—don’t let this fool you. Evercrisp seems to do the same for starch staining as its Fuji parent.

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.
• Starch: 1 = all starch, 8 = No starch; range is of all fruits tested. Using Cornell Starch Iodine Index Chart.