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Healthy Fruit 2010 Vol. 18:17

Aug 24, 2010

Marshall McIntoshBuckeye GalaHoneycrisp

Orchard Radar preliminary McIntosh harvest date forecasts (for Belchertown)

Begin measuring actual McIntosh starch-iodine index no later than Wednesday, August 18

The Michigan formula estimate for standard (i.e. non-spur) McIntosh starch index 4.0 and beginning of optimum McIntosh harvest for CA storage is Wednesday, August 25. Estimate adjusted to lessen influence of unusual bloom date is Tuesday, August 31

Cornell Bulletin 221 provides formulas for different locations to estimate date when non-spur McIntosh reach starch index 6.0 and the end of optimum harvest for CA storage. Using the Hudson Valley formula, the estimated end of McIntosh CA harvest for Belchertown MA is Wednesday, September 15

The way I see it

I am not so sure apple harvest is all that far ahead of average. No more than a week or so. Although I keep flip-flopping -- maybe 7-10 days ahead of last year and average. GingerGold, Zestar!, and Paulared harvest has been in full swing for about a week and will be over this week. (Except for GingerGold.) I don't expect Mac harvest to begin until next week at the earliest, although they are close and some drop is seen. Fruit seems loose too. What we need now are some cooler nights to stimulate red color development. For all practical purposes, next week will be like the second week in September in a 'normal' year, so I expect harvest of early-mid season varieties like McIntosh, Gala, and Honeycrisp to be underway if not sooner. JC

Apple maturity test results

date Cultivar pre-harvest drop fruit diameter inches color % red firmness lbs soluble solids starch index
8/24/2010 Marshall McIntosh some 3.1 60 15.2 (11-18) 11.9 4 (3-6.5)
8/24/2010 Buckeye Gala none 3.0 95 18.9 (16-23) 12.5 4 (2.5-6.5)
8/24/2010 Honeycrisp few 3.2 45 13.3 (12-15) 11.6 4.6 (2-6.5)

Comments: harvested at UMass Cold Spring Orchard, Belchertown. Marshall McIntosh treated with ReTain last week. All three of these cultivars are at the 'tipping point' in terms of harvestable maturity. Spot picking could begin anytime and will be underway next week.

Honeycrisp storage recommendations

A reminder that there are a couple of recommendations for storing Honeycrisp apples to prevent soft scald and cold injury. These include:

  • pre-condition just harvested fruit at a temperature of 50-70 F. for 5 or more days
  • store at a temperature of 38 degrees F.

You should also consider applying a pre-harvest fungicide such as Pristine to Honeycrisp to help prevent storage rots.

Guest article

SUMMER ROTS Janna Beckerman, Dept. of Botany & Plant Pathology, Purdue University Extension. Reprinted from Ohio Fruit ICM News, Volume 14, Issue 14

Hot, wet weather has greatly increased the incidence and severity of summer rots this year. Summer rots can be caused by Colletotrichum acutatum, Colletotrichum gloeosporioides (also called Glomerella cingulata because these names aren't quite long or confusing enough). Two other closely related rots, white and black rot, caused by Botryosphaeria dothidea and Botryos- phaeria obtusa round out our perpetrators. There are a variety of apple summer rots, but as a group these fungi infect, causing small dark spots that appear on fruit surfaces in July and August (and later on late-maturing fruit). These lesions can increase in size to cover most of the fruit by harvest, making infected fruit unmarketable.

In the case of the Colletotrichum species, symptoms do not develop until the fruit begins to mature. This means that spraying needs to occur prior to the observation of symptom development especially in wet years, and particularly for sensitive cultivars like Honeycrisp, Empire, Golden Delicious, Fuji, Granny Smith, Ida Red, Stamen and the highly overrated Arkansas Black. The rot begins as a small, light brown, circular lesion. As lesions enlarge, they change to a dark brown and form sunken or saucer-shaped depressions with fruiting bodies of the fungus appear near the center of the lesion. Under wet and humid conditions, large numbers of salmon pink spores are produced in an oozing mass, which occur concentric circles. The rotted flesh beneath the surface of the lesion is watery, appearing in a V-shaped pattern in cross section that narrows toward the core.

Black rot, caused by the fungus Botryosphaeria obtusa, is the fruit infecting stage of frog-eye leaf spot. Fruit infection usually occurs early in the season at the calyx end of the fruit, and results in blossom-end rot later in the season. Early lesions are often overlooked as reddish spots that expand and become brown on mature fruit. As the rotted area expands, a series of concentric bands form creating a target pattern of black and brown. Careful examination of the fruit may reveal black pustules (pycnidia) that erupt on the surface of the infected fruit. Empire, Northern Spy and Cortland may be slightly more susceptible to black rot than other cultivars.

Black rot's evil twin, white rot (caused by Botryosphaeria dothidea and also called bot rot), only infects fruit and wood (no foliar infections). New infections should be visible by now, and appear as small, circular spots or blisters that expand from lenticels. As the lesions expand, the area becomes depressed and a watery exudate may appear on the bark around the blisters. On the fruit, infection can be seen four to six weeks before harvest and develop with fruit maturation. Lesions begin as small, slightly sunken brown spots that expand, rotting the entire fruit to the core the core. Red-skinned apple cultivars may "bleach" as they rot, thus the name, "white rot." Black pustules may be visible on extremely rotted fruit. Of all the rots, I've observed this one the least in Indiana. Golden Delicious, Akane, Empire, and Jersey Mac seem to be most severely affected, and should be looked upon as the "canaries in the coal mine."

Useful links

UMass Extension Fruit Program

Scaffolds Fruit Journal

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