Aug 31, 2015

Harvest practices to prevent postharvest disorders in Honeycrisp

There are many factors that affect Honeycrisp storage behavior, and some occur during harvest. Spot picking fruit at the optimum stage of maturity, compared to slightly immature, can reduce bitter pit, whereas soft scald and soggy breakdown can be reduced by harvesting fruit before it becomes over-mature.

With support from Pennsylvania growers and packers, we have been conducting research the past three years that provides some guidance for harvesting this temperamental cultivar.

Following the 2014 harvest season, growers from regions around the state reported excellent Honeycrisp fruit quality – in some cases, the best they had ever seen. But several months following storage, a number of disorders started to appear.

Ben Rice, Rice Fruit Company, calculated that 2014 packouts were reduced by an average of 17% for soggy breakdown, 8% for bitter pit and 3% due to senescent breakdown, for a total of $2.8 million in losses. Other packers reported similar percent losses, with fruit rots being an additional concern. Soggy breakdown is a chilling injury like soft scald and was likely associated with the cooler than normal harvest season.

Harvesting Fruit at the Optimum Stage of Maturity

A spreadsheet tool to help you assess whether increasing the number of times you harvest Honeycrisp will be cost-effective based on potential reductions in premature fruit drop and bitter pit is now posted at the Penn State Tree Fruit Production website. Sample increases in packout are based on our 2014 storage trials conducted on fruit segregated by background color following commercial harvest. Fruit from three different growers were segregated into three treatments:

1. Fruit harvested with a background color that was slightly too green
2. Fruit harvested at the optimum ground color of very light green to light yellow
3. Fruit harvested with a deeper yellow background color

These fruit were then stored for 4 months at 38°F and evaluated for the incidence of storage disorders.

Fruit harvested slightly immature, or 3 versus 5 times, had 60% more bitter pit. Fruit harvested at an overmature stage, had 40% more soft scald.

Senescent breakdown, soggy breakdown and soft scald are more prevalent when fruit are harvested when over-mature. While red color development is desirable, it is important to also consider potential losses to chilling injuries and senescent breakdown.

Assessing Which Honeycrisp Apples are Ready to Spot Pick

The summer issue of Massachusetts Fruit Notes has a ground color chart that Duane Greene and Jon Clements found to be useful when harvesting Honeycrisp. The authors reported that when starch readings average about 6 on the Cornell starch-iodine index you should begin spot picking Honeycrisp, selecting fruit that have a background color of light green, white or light yellow and a pink blush turning to red.

Harvesting Honeycrisp at Optimum Maturity also Increases Consumer Acceptance

Another important reason for harvesting Honeycrisp at the proper stage of maturity is thatprior sensory evaluation trials on PA fruit determined that consumers can readily detect the inferiority of apples harvested immature (Baugher et al., 2010). Consumers found fruit from heavily or lightly cropped trees to also be inferior in taste.

Photo: Fruit spot-picked at three stages (left to right – slightly immature, mature, slightly overmature) for taste tests conducted by a sensory evaluation panel.

100 panelists participated in this study conducted at the Penn State Sensory Evaluation Laboratory.

Increasing Calcium Levels in Fruit Relative to Nitrogen, Potassium and Magnesium

When you complete the final spray in your season-long calcium program, you should have applied a total of 9 to 14 lbs of actual calcium to your trees in order to influence both bitter pit and storage life. Recent research comparing calcium materials confirmed that these higher levels of elemental calcium are more efficacious on Honeycrisp (Greg Peck and Alan Biggs, 2015). Rob Crassweller and Lynn Kime developed a useful on-line spreadsheet to help with this calculation.

In our 2014 Honeycrisp research in commercial orchards, bitter pit was reduced when the level of calcium was high relative to nitrogen, potassium and magnesium. There was an interaction with crop load, with bitter pit further reduced at moderate crop loads.

Stem-Clipping to Increase Packouts

New York growers have more experience than we do with stem clipping fruit to prevent stem punctures and subsequent fruit decay. Growers and packers report a 5% reduction in decay with stem-clipping, and Lynn Kime developed another spreadsheet calculator to help you determine if this practice is cost-effective in your operation.

Research on Honeycrisp Continues

Our research on Honeycrisp continues this season. In addition to conducting a fourth year of field trials, we are cooperating with Chris Watkins, Cornell University, on a third year of storage studies with PA fruit. Chris will be the featured speaker at a special Honeycrisp Symposium to be held the opening day of the 2016 Mid-Atlantic Fruit and Vegetable Convention.

— Penn State University