MSU Extension Apples

General comments

Harvest in the Grand Rapids, Michigan, area is approaching the halfway point as Gala harvest is nearly complete and all Honeycrisp blocks have at least one picking completed. McIntosh harvest is complete. Some Golden Delicious are now being harvested as are Jonathans and Jonagolds. In general, fruit size is good to very good for most varieties. Gala are on the smaller side this year. Overall, growers are reporting picking out a bit short or right on target. In general, fruit finish is very, very nice and fruit quality is very good. The weather for harvest has been favorable and labor is adequate for most growers.

Continued reports are coming in of San Jose scale on harvested fruit from hot spots in apple orchards. There is nothing one can do at this point to manage scale, but make a note of any problem areas to target for 2019. Our regional trap numbers for brown marmorated stink bug (BMSB) are higher than they have been all year. Consider border insecticides on late season apples in areas with known BMSB pressure to prevent injury.

Summer diseases (sooty blotch and flyspeck) are starting to show up in orchards where fungicide covers have been reduced by rainfall and not reapplied. Once the signs of these diseases are visible, there is little you can do to remove it. Apple scab seems to have restarted some fruit infections with the wetter weather in the past few weeks. Keeping a level of fungicide on fruit at harvest will help prevent pinpoint scab from developing in storage to prevent any “surprises” when rooms are opened several months from now.

Week four of our Grand Rapids area apple maturity sampling continues to show fruits with higher than expected starch clearing, but ethylene is still low and these two parameters don’t correlate as usual this season. This is most likely due to the heat we’ve experienced all summer and into harvest, and some varieties seem to respond to summer heat more so than others. Your MSU apple maturity team observes that Gala, Honeycrisp and Fuji respond to a warmer summer with earlier maturity. Red Delicious, Golden Delicious, McIntosh, Ida Red, Rome and perhaps Cortland seem to not change in their maturity in a hot summer. It is also thought that Jonathan and Jonagold are somewhere in between.

For the Grand Rapids area, apple maturity seems to continue to run close to our 2018 predicted apple harvest dates with some sites or varieties being slightly ahead as mentioned above. Our predicted harvest dates are for PEAK harvest, so some fruits might be ready ahead or behind these dates as we move through maturity. When we sample apple varieties, we try our best to collect random samples from blocks untreated with harvest management products.

Apple variety sampling results

Gala harvest is nearly completed and only fruits treated with harvest management tools are left. Our sampling this week shows 100 percent of fruits have ethylene over 0.2 ppm. Red color is greatly improved on Gala this week at 93 percent. Background color is low or yellow. Firmness is still very good at an average of 17 pounds, which is down from 20.1 pounds last week. Starch clearing made a big leap forward from 5.8 last week to 7.1 this week. Brix are a little on the low side at 12.5.

All Honeycrisp blocks have had at least one picking and some are following up this week with the second pick. Internal ethylene is very high as is typical in Honeys. Color in second pick fruit is on the low side as usual—this is reflected in our samples this week where red color dropped from 68 percent to 63 percent. Background color is also tending to be more green than last week due to only greenest apples remaining. Firmness is down significantly from 15.5 pounds last week to 13.8 pounds this week. Starch clearing is high as is typical for Honeycrisp. Brix levels are still very good at 12.9, but down slightly from last week.

We sampled Empire for the third week and this week’s samples show a definite shift in maturity to indicate Empire is ready for long-term CA storage this week. Our predicted date for Empire peak harvest in the Grand Rapids area is Sept. 24 and it appears this date was on target this year. Internal ethylene is still very low with no fruits over the 0.2 ppm climacteric. Red color improved from last week’s 48 percent to 66 percent red color this week. Background color continues to be lower than expected at 2.1 on average. Firmness is still very good at 15.9 pounds pressure this week and this is a drop from 19 pounds last week. Starch index readings for this week are lower than last week, which is quite strange. Brix have improved a bit from 11.8 last week to 12.2 this week.

Jonagold harvest is beginning on the Ridge. The predicted harvest date for Jonagold is Sept. 26, which seems to be holding as a target date for peak harvest or at least to get started for long-term CA storage if not treated with harvest management applications. There continues to be very little internal ethylene present, with only 10 percent of fruits sampled this week over the 0.2 ppm level. Red color improved a great deal this week at 62 percent red color compared to only 34 percent last week. Background color is more yellow than green over last week. Firmness is excellent in Jonagold as expected, with an average of 17.4 pounds. Starch levels are higher than expected at 5.1, but they have moved very little from last week and probably not a good indication of maturity by itself this year. Brix levels continue to improve at 13.1 this week compared to 12.5 last week.

Golden Delicious sampled this week show a marked improvement for all maturity indices. The predicted harvest date for peak harvest in the Grand Rapids area is Sept. 28 and some harvest began on the Ridge this week. Firmness is very good at 15.7 pounds. The starch clearing ratings are all over the board in our sample with an average of 5.7, which is up significantly from last week’s 1.7. Brix are about the same at 13.8 this week from last week’s 14.4. Golden Delicious is now in the long-term CA storage window in the general Grand Rapids area. Fruit size and finish are very good in Goldens this year.

Red Delicious were sampled for the first week and we should have looked at them sooner. The predicted harvest date for Reds in the Grand Rapids area is Oct. 2, which should shape up to be an accurate target. Only 10 percent of fruits are over 0.2 ppm internal ethylene. Red color is very good to excellent depending on the strain. The background color averages 1.3 and can be a bit difficult to determine on highly red cultivars. Firmness is excellent at 16.7 pounds pressure. Starch clearing results range from 1 to 3, with an average of 2.1 indicating they are still on the immature side. Brix is quite low as is usual for Rec Delicious at 10.4.

Next week we will add all the late harvested varieties to our samples: Ida Red, Fuji, Rome and more.

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

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