MSU Extension Apples

General harvest comments

Harvest of Ginger Gold, Wildfire Gala, Zestar!, Premier Honeycrisp and SweeTango is underway. Although many growers are eyeing calendars and thinking that it’s starting to get close to being standard-season Gala and McIntosh time, data from this week indicates we’re still well off from that mark. Harvest dates for most prominent commercial varieties are looking to be running at least a week late this season throughout the region. Harvesting any apple variety early can lead to an increase in post-harvest storage disorders, including bitterpit. Therefore, it is in your best interest to wait until fruits are at the optimal condition for controlled atmosphere (CA) storage in order to avoid economic loss down the road, difficult as it is to keep crews away from fruit during a slow season.

Weather for coloring continues to be outstanding, and you can really see the results in our early varieties as bins come out of orchards. Growers have waited a couple of years for this; late August has not been kind to early varieties in the last two years as punishing heat has kept color development poor and made fruit soft. Fruits coming off of trees this season look beautiful by comparison, and growers are happy to be capitalizing on the quality.

The timing for ReTain applications is either upon us or quickly approaching for several important commercial varieties, so make sure you have your plan together for timing and rates. You can check out a few good ReTain reminders by reading the Michigan State University Extension article, “ReTain and NAA as a standard practice for apples.”

For those looking at short range applications (14 days before harvest or shorter,) remember that NAA can be added at 10 ppm to help with stop-drop. NAA delays the formation of the abscission zone (the spot where the stem separates from the spur), but also stimulates biosynthesis of ethylene. For this reason, combining NAA with ReTain gives us the best of both worlds. The NAA slows the formation of the abscission zone leading to less fruit drop, and the ReTain shuts down the biosynthesis of ethylene, allowing us to capitalize on the advantages of NAA as well as the other benefits of ReTain (delaying harvest, improving firmness, less greasiness, less cracking, etc.).

Growers using ReTain 30 days before harvest at full rates do not need to add NAA to this application, but NAA is helpful at the 30 day pre harvest interval when using a reduced rate (one-half, one-third or one-fourth pouch) on varieties with high sensitivity (Gala, Jonagold) or moderately high sensitivity (Honeycrisp).

Growers spraying a pre-harvest fungicide to protect against pin point scab and/or storage rot fungi are reminded that strobilurin fungicides (Flint Extra) as well as first generation SI fungicides (Indar, Rally) do not provide reliable apple scab control in Michigan. SDHI fungicides are a good choice for a pre-harvest spray since they provide excellent broad-spectrum disease control on fruit and will take care of any apple scab spores that might be around to cause pin point scab.

Insect update

We are near the end of the insect management season, but not quite there for many growers. Apple maggot is still active. Pressure is not generally high this year but as always there are high pressure sites that are still pulling large numbers. Red sphere traps should be baited with apple volatile to improve efficacy, and the threshold for these traps is five apple maggot flies.

Second generation codling moth is declining and many traps have fallen down to zeros in the past two weeks. After a biofix is established, target an application of insecticide at about 250 growing degree days base 50 from that catch date, as this will coincide with the start of egg hatch. Most blocks are now past this mark, but there are later sites that have recorded stronger flights in the past week or two that will still need one more insecticide before growers call it a year. A late start to the season means that we do not anticipate a third generation of codling moth this year.

Brown marmorated stink bug pressure continues to be low so far this season in west central. Areas in the southern part of the state have reported an uptick in brown marmorated stink bug adult activity in the past seven days, but that has not occurred here thus far. We will continue to monitor for brown marmorated stink bug until harvest is concluded, but risk for the west central region looks low at this time.

Second generation obliquebanded leafroller flight is declining or over, the timing for treatment is 400-450 growing degree days base 42 after you biofix an orchard. Third generation of oriental fruit moth is declining or over at most locations. The timing for an application targeting oriental fruit moth is 200 growing degree days base 50 after you biofix an orchard.

Individual variety maturity results

The scales used to rate these different metrics on these charts are as follows:

• Background color: scale 1-4, 1 is fully yellow and 4 is fully green.
• Russet: 1-4, 1 is no russet and 4 is severe russet.
• Pressure: always listed in pounds, and two pressure scores are recorded for each apple tested.
• Watercore: 0-4, 1 is no watercore and 4 is severe watercore.
• Bleeding: 0-4, 0 is no bleeding of red color into flesh and 4 is severe bleeding of red color in to flesh.
• Red: listed as a percentage of the whole fruit with red color.

Ginger Gold

Don’t read too far into this week’s starch index values—this variety doesn’t test too far above 1s and 2s when it’s at acceptable quality for harvest for the fresh market. It is eating very nicely this week and is ready for harvest throughout the region. There is a nice side blush of pink on Ginger Gold this season. Experience tells us that delaying the harvest of this variety is not wise, it is prone to getting soft very quickly.

Premier Honeycrisp

This strain of Honeycrisp matures at least two weeks earlier than standard-season strains and is ready for harvest in west central Michigan. Premier Honeycrisp is generally a nice looking piece of fruit and has some distinct features. It seems prone to having a green background color underneath the splash of red rather than a yellow or green-yellow background. It generally displays a striped red rather than a blush red, tending to look similar to the original strain of Honeycrisp in this respect. It does not get as red as some of the redder standard season Honeycrisp strains that are now available (Firestorm, etc.), but still gets an acceptable side of color when exposed to sunlight properly.

Due to the early season of the strain, excellent summer pruning to improve sunlight exposure will likely be extremely important to allow it to get color in time for harvest, especially in a warm year. This strain also seems to move from immaturity to maturity extremely fast, so be cautious in the future with delaying harvest once they test in the mature range. Reduced ReTain rates with NAA will also be an option if you want to delay or stagger harvest of the strain.

Zestar!

Zestar! moved along significantly in a week and is ready for harvest. Growers started spot picking this variety last week and in the first half of this week, and harvest will conclude by the end of the week for most. This variety picked up a nice amount of color in a week, and is eating well right now. Zestar! tend to move from a good eating apple to over-mature quickly due to their softer texture, so growers will want to get through harvest quickly.

McIntsh

McIntosh is moving very slowly this year, so do your best to control the urge to get into it at a normal time to avoid issues associated with premature harvest. Starch index values moved ahead marginally in a week’s time; this variety still needs at least a week or two for even the earliest processing growers. Brix did pick up nicely in the past seven days and firmness seems to be holding at acceptable levels. However, fruits are still extremely starchy and could stand to pick up a little bit more size too.

Early Fuji

Early Fuji is still a week or two away from harvest. Fuji is considered mature for CA storage at a starch index of 3, with suggested firmness between 16-18 pounds. Fruits sampled this week were well shy of both these marks. Color was also very poor at both sampled locations this week, so another week or two of waiting will help growers out this year. More great coloring weather on the forecast should help move color along in the coming days.

Gala

Gala would normally be picked at earlier sites starting in the second week of September in west central Michigan, but that’s not happening this year. Even the earliest sites that were tested this week (Elbridge, New era, etc.) were looking to be two full weeks away from peak maturity, and sites in Mason County and closer to the lake in Oceana County may be looking at closer to three. Size looks pretty good on Gala this year for the most part, although a couple of the sites that were tested this year could stand to pick up a little bit more.

Color looks absolutely outstanding this year, so this is going to make waiting really difficult because Gala looks much further along than it actually is right now. Don’t be fooled by the red color; picking standard season strains of Gala any sooner than mid-September this year will likely result in premature harvest issues coming out of storage. Gala is considered mature for CA storage at a starch index of 3 and firmness between 16 and 18 pounds. No site had an average starch index value of more than 1.3 this week, and fruits are still hard as rocks.

*Firmness is measured with a mechanical 11-mm wide probe inserted into the pared flesh of a fruit to a distance of 8 mm. 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.)