MSU Extension

General comments

The predicted apple harvest dates in the Grand Rapids, Michigan, area, continue to run ahead of the normal average dates by about a week, with some blocks slightly ahead of predictions and some slightly behind. It certainly is a different year for predicting apple maturity with mixed maturity on the trees due to the long, drawn out bloom and then the very hot summer temperatures. We are seeing maturity moving more quickly than expected in some varieties, so continue to check your blocks often for maturity parameters.

One note on the recent warm weather is there are reports of high CO₂ levels in rooms after they are closed due to very warm fruit respiring. Be sure you have that fruit cooled down well before sealing everything up. Adding a half skid of lime in the room will help as well. There can also be issues when applying 1-MCP in the room with warm fruit. For instance, Golden Delicious will get a “ghosting” on the surface if 1-MCP is used on warm fruit.

Water core

Given the high amounts of rain that some areas have received in the last six weeks, you should pay close attention to water core in varieties that are highly susceptible to it this season and harvest accordingly. High water core presence reduces storage-ability. Surprisingly, water core on early varieties has not been unusually high, but that could change.

Fruit rot potential

Fruit rot potential is higher than usual for the 2016 season due to high amounts of rainfall in the recent several weeks. The best place to manage fruit rots is with fungicides applied while fruit are on the tree. We don’t dip any longer and fungicides were added to the DPA. We fog with DPA, but the post-harvest fungicides are no longer routinely used. With a big crop potential, it is likely that fruit will be stored a long time with more potential for rot to develop.

Superficial (storage) scald

Very warm temperatures in August and September and possible poor red color could lead to higher incidence of scald in susceptible varieties. Treat fruit rapidly after harvest with DPA or 1-MCP to minimize risk.

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.
• Brix = % sugar measured with Atago PAL-1 Pocket Refractometer

Variety sampling results

The majority of Gala on the Ridge have been harvested. There are a few left and they are quickly moving into the short-term storage window, even if treated with ReTain or Harvsita.

McIntosh harvest began in the Grand Rapids area last week and fruit quality is very good. There are a few blocks with frost marks and overall color could be a bit better. McIntosh with no harvest management applications are quickly moving into the mid to short-term controlled atmosphere (CA) storage window.

The majority of the Honeycrisp crop was harvested in the past week or so on the Ridge. There are still fruit to be color picked, but a lot went into bins recently. Our samples from this week indicate any Honeycrisp that was not treated with AVG or 1-MCP in the orchard is in a window for fresh sales. Treated fruit are very quickly moving into a mid to short-term window for any long-term storage. Keep in mind that when Honeycrisp are in the very mature range, they are more subject to chilling injury in storage.

Empire seem to continue moving very slowly through the maturity process this year. Many will begin harvest this week on the Ridge and they are just moving into the ideal range for long-term CA harvest.

Jonagold is still immature, but they have moved rather quickly forward compared to last week. Our predicted harvest date is Sept. 29, which is very close to a normal average harvest date and may be on the late side for predictions this year. Jonagold are getting close to the long-term CA storage window. If cool weather moves in and color development occurs, some picking could begin early next week.

Jonathan (Jonee) are a similar story as Jonagold. Maybe the Sept. 29 predicted date is a bit on the late side. Some Jonathans have already been harvested for taffy apples, but any long-term CA fruit is about a week away from first picks.                 

Cortland is immature with starch readings of 1’s and 2’s and background color of 4. Brix are not that bad for Cortland at 11. Cortland harvest is usually between Jonagold and Red Delicious harvest, and they need some time yet to mature.

Golden Delicious was sampled for the first week. They are immature according to the various measurements, however they could move forward very quickly and they actually eat OK. Our predicted harvest date is Oct. 5 and that might be on the too-late side. Keep a close eye on Golden Delicious and harvest accordingly.

Nova Spy was sampled for the first time this week. They are very immature, but farther ahead than expected. Nova Spy harvest is typically slightly ahead of Northern Spy.

Apple storage parameters for different varieties

*Firmness is measured with a mechanical 11-millimeter wide probe inserted into the pared flesh of a fruit to a distance of 8 millimeters. Starch index is measured on equatorial cross section of an apple stained with iodine solution and rated using the Cornell University starch-iodine index chart for apples on a 1-8 scale (Predicting Harvest Date Window for Apples by Blanpied and Silsbey, Cornell Extension Bulletin 221.)

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