MSU Extension

General comments

Even though we are past the peak of harvest bushel-wise, there are still a few weeks to go to get it all in the bins. Some cooler weather has helped to improve color, but it is still a bit lacking.

We continue finding brown marmorated stink bug adults and their damage – last week it was found in Red Delicious and Jonagold. 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. Bitter pit damage at harvest is typically very shallow and brown marmorated stink bug damage will go much deeper. Make notes on blocks with brown marmorated stink bugs issues this year so you can target them in late summer next year.

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 or 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

Red Delicious was sampled for the third week and they continue to move forward slowly, which is typical for Red Delicious. Internal ethylene remains very low as per usual and starch conversion has moved only slightly. Many Red Delicious went into bins in the Grand Rapids, Michigan, area in the last seven to 10 days. For those remaining on trees, they are in the mid-term controlled atmosphere (CA) storage window still, but water core and a little moldy core are being reported, so don’t let them go too long if you plan to store them for more than short-term sales. Our predicted date for peak Red Delicious harvest was Oct. 5.

Ida Red was sampled for the third week and is now in the nice range for long-term CA storage. Our predicted date for peak Ida Red harvest was Oct. 10. Many, if not all, Ida Reds have been harvested in the past week.

Cameo was tested for the second time this season. We still aren’t sure where to put Cameo on the harvest schedule – it does hang and stay hard for a long time, so you can get to them when time permits. At this time, our tests still indicate immature fruits for Cameo, but they have changed from last week; background color is lower (less green), starch clearing made a leap forward. Brix levels are still 12.2 on average and fruit firmness is still very high. Cameo harvest can begin at any time for long-term CA storage, but they could hang for another week quite well too.

The predicted date for Rome in Grand Rapids is Oct. 15, which is a good target date – they have moved slightly forward in their maturity and harvest can begin any time for long-term CA storage. There has not been much bleeding reported, but it should begin soon and timely harvest will be important to avoid it.

Late-season Fuji varieties have fooled me once again this year. Last week’s samples made me nervous that this variety was farther ahead in maturity than expected, as the predicted harvest date is Oct. 25. This week’s samples show very small movement forward in maturity. We saw the same scenario last year. We think the Oct. 25 date might be about a week too late and harvest for long-term CA storage could begin around the middle of next week in the Grand Rapids area.

Internal ethylene shows 100 percent of fruits now with levels over the 0.2 ppm climacteric. Once that level is reached, fruit should move forward in their maturity and there’s no holding them back once it’s reached. The background color is moving from green to more yellow or white, but still very slow to change. Firmness is excellent, as is usual for Fuji. Starch and Brix levels are improved over last week. We are seeing a marked increase in water core compared to last week’s sampling. The water core is still very low, but it is overall increasing and will continue to increase over the next two to three weeks. High incidence of water core shortens the storage life of apples. 

This is the second week of Evercrisp sampling. The numbers show a movement forward in maturity and we still need to figure out where this new variety fits in the Michigan harvest schedule. We are told it matures quite late and stays hard for a long time on the tree.

Granny Smith continue to be immature, as expected.

We will continue to sample remaining varieties for at least one more week.

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