MSU Extension

General comments

The majority of the 2016 apple harvest is past a peak stage for the general Grand Rapids, Michigan area, with two to three weeks of push to go. In the last week, Golden Delicious, Red Delicious and Jonathan have been the major varieties going in the bin. Most growers are looking at Jonagold and waiting for better color. Labor sourcing continues to be reported as adequate for many growers, with some smaller acreages reporting a bit of difficulty finding enough workers.

We continue finding brown marmorated stink bug adults and their damage. Many reports came in last week from Gold Delicious because symptoms show up so readily in this variety. If you see damage that looks like bitter pit at first glance, please look closer – it is very difficult to tell the difference between bitter pit and stink bug injury. Typically bitter pit is on the calyx end of the apple and stink bug injury can be anywhere on the fruit.

We have increased our trap numbers for brown marmorated stink bugs, but this pest is evasive and we found damage about the same time we started catching them in traps, which is about two to three weeks after the damage was done. Finding brown marmorated stink bugs prior to damage is a problem everywhere this pest is found and it will be the biggest challenge in the future. Make notes on blocks with brown marmorated stink bug issues this year so you can target them in late summer next year.

Moldy core versus callus tissue formation

Some apple varieties are more susceptible to moldy core (Red Delicious, Fuji). The packing tolerance for the presence of moldy core is very low, so packers are always on the lookout for it. Last fall and now again in 2016, we are seeing a higher incidence of callus tissue present inside the seed cavities of some apple varieties, and it’s being confused with moldy core by the untrained eye. While moldy core can look whitish in color, it usually is grayer as these fungi tend to be, and if you poke at it or grab it with forceps, it is easily removed. The callus tissue is very white and is a part of the seed carpels and not easily removed.

Water core

The rains continue to be above normal, and water core should be on your radar for varieties susceptible to it (Red Delicious and Fuji in particular). High water core presence reduces storability. I had mentioned that surprisingly, water core on early varieties has not been unusually high, but that could change and it is beginning to; we are now seeing and hearing of water core presence in Reds and Fuji.

Fruit diseases – rots and summer diseases

We continue seeing higher incidence of fruit rot in some blocks. Summer diseases have also very much increased with the near ideal environmental conditions for this complex of fungi. All fruit remaining on trees is very susceptible to summer diseases from now until harvest. If you have late varieties that have 10 to 14 days before you harvest them (Fuji, in particular), a fungicide application for summer disease and fruit rots should be considered in light of recent heavy rainfall totals. Fruit is essentially uncovered if you have not sprayed in the last week or so. Captan alone is not enough to prevent summer diseases and an SDHI fungicide is highly recommended.

Rodent activity

Keep an eye out for rodent activity in your orchard blocks to help determine where highest pressure might be. High population blocks might need two management rodenticide applications compared to lower populations. Look for evidence of mice and rabbits feeding on fallen fruits in already harvested blocks and for trails in orchards and along ditches.

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

Most Gala on the Ridge have been harvested, but we did have some fruit to test this week still remaining. They are now in a fresh sales and short-term storage condition.

There are few Honeycrisp yet to be picked for second and third picks. They are in fresh sales condition or could be stored short term.

Jonagold not treated with harvest management materials is quickly moving into the mid-term controlled atmosphere (CA) storage window. Very few Jonagolds have been harvested on the Ridge as most are waiting for color, which is slowly improving.

Many Golden Delicious have been harvested in the last week. As predicted, they are quickly moving from a long-term CA window into a mid-term CA storage window with the sampling parameters from this week. Our sample indicates a still green background color, but in many Goldens still hanging, the background color is now white to yellow. Starch levels continue to creep up as fruit mature as well.

Red Delicious was sampled for the second week and they have moved forward very little as is typical for Reds. Our predicted date for peak Red Delicious harvest is Oct. 5, which seems to be on target still and growers have started on Reds in the last few days. We are hearing of water core and moldy core in Reds, so keep an eye out for that and store fruit accordingly. Red Delicious is still in the long-term CA storage window.

Cameo was tested for the first time this season. I am still not sure where to put Cameo on the harvest schedule – I still hear many different dates from different growers. I hear some get to it after Red Delicious, some tell me they target Cameo for harvest about a week after Rome or maybe in the Fuji window or a little later. Cameo does hang and stay hard for a long time, so you can get to them when time permits. At this time, our tests indicate immature fruits for Cameo for this first week of sampling.

Ida Red was sampled for the second week and is slowly moving forward in its maturity, but still immature at this time in the Grand Rapids area. Our predicted date for peak Ida Red harvest is Oct. 10, which now looks to be just about right.

The predicted date for Rome in Grand Rapids is Oct. 15 and early sampling indicates Rome is still immature as expected.

Late-season Fuji varieties appear to be farther ahead in maturity than expected as the predicted harvest date is Oct. 25. We saw the same scenario last year. One more week of sampling will give a better picture of where Fuji is moving. They are still immature. Some water core is beginning to be reported in Fuji.

Evercrisp sampled this week are immature. This new variety matures quite late and stays hard for a long time on the tree. We still need to work out exactly where it fits in our harvest schedule.

Granny Smith are immature as expected.

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