Location: Physiology and Pathology of Tree Fruits Research
Project Number: 2094-30600-001-018-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Dec 1, 2025
End Date: Nov 30, 2028
Objective:
1. Determine optimal maturity range for minimizing soft scald incidence.
2. Means of most accurately referencing harvest maturity for ‘Sugar Bee’.
3. Establish orchard temperature events elevating soft scald risk.
Approach:
‘Sugar Bee’ is a promising flagship club variety with superior firmness/juiciness and eating quality retention characteristics potentially allowing for a year-round market supply from member WA producers. While appearance and eating quality are easy to maintain with conventional storage technologies, the apple can develop soft scald and internal browning related to CO2 sensitivity during CA storage. CO2-related internal browning is associated with more mature apples and can be controlled with diphenylamine drenching. It has been reduced significantly or eliminated by scrubbing CO2 from the rooms. However, soft scald is far more challenging without any consistent controls. Along with advanced maturity, soft scald and the internal form of the disorder, soggy breakdown, disorder risk is associated with cold temperatures in the orchard around harvest and the transition to storage temperatures. Consequently, conditioning ‘Honeycrisp’ a soft scald/soggy breakdown sensitive variety and parent of ‘Sugar Bee’ at 50 F for 7-10 days is the conventional approach to mitigating these disorders. This procedure, while effective in reducing symptoms of soft scald/soggy breakdown, does not ‘cure’ chilling injury in each lot in either cultivar. Furthermore, while well-established for ‘Honeycrisp’, varietal differences require examination of the impacts of orchard temperatures in the weeks preceding harvest and relative harvest maturity to best augment temperature conditioning mitigation protocols. Determining optimal harvest maturity in combination with cumulative chilling in the orchard will be the first step to reducing ‘Sugar Bee’ cold chain losses.