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Postharvest Issues with ‘Honeycrisp’ Apples

‘Honeycrisp’ is being extensively planted in Ontario and consumer demand continues to increase. This apple cultivar has outstanding flavor characteristics and can remain crisp for several months during storage. However, there are several major maturity and storage problems associated with ‘Honeycrisp’. These include (in somewhat order of severity):

1. Bitter pit – more than 50% of apples in some years and at some locations may be unmarketable due to bitter pit
2. Soft scald – up to 100% of the apples may develop soft scald during storage under certain conditions
3. Variability in fruit coloration – attractive red blush, coarsely-striped, poorly-colored, and/or blotchy coloration; suggests multiple strains of ‘Honeycrisp’ may already exist in commercial plantings
4. Uneven maturity – fruit mature very unevenly, so multiple harvests are necessary
5. Immature apples – fruit from over-cropped trees may never mature and thus remain of poor eating quality; fruit harvested too early never develop varietal flavor and remain almost tasteless

Researchers at Cornell University have been investigating these challenges with ‘Honeycrisp’ for the past few years. The following summary highlights some of the research results and recommendations from the various scientists.

Watkins et al.

• Major factors that have been implicated in soft scald development include over-maturity of fruit at harvest, climate (dull, cool, wet summers), light crops, large fruit, and vigorous soils.
• Soft scald (and soggy breakdown) increased with exposure of fruit to storage temperatures of 33 F (0-1 C), especially those from late harvest dates
• Storage at 42 F (5-6 C) controlled soft scald (and soggy breakdown) but also resulted in higher decay and less acceptable flavor
• DPA did not prevent soft scald development in fruit stored at 33 F (0-1 C) but did control it in fruit stored at 37 F (2.5 C)
• One week delay at 50 F (10 C) prior to storage controlled soft scald development (and soggy breakdown), but bitter pit incidence was substantially increased
• Fruit firmness was not affected by storage temperature, DPA treatment, 1 week delay at 50 F prior to storage, or shelf-life of 7 days at room temperature
• No consistent association of internal ethylene concentration to harvest date and soft scald incidence was found
• Starch may be a useful guide to over maturity – suggest a starch index of 6 (Cornell chart of 1 to 8) as a cut-off to harvest fruit for long-term storage
• Storage temperature of 38 F (3-4 C) recommended
• For best post-storage eating quality, fruit should be harvested with a minimum firmness of 13.5 lb and at least 13% soluble solids

Rosenberger et al.

• Early harvest, delayed cooling, and warmer storage temperatures favor the development of bitter pit
• Calcium chloride (CaCl₂) provided the best control of bitter pit
• CaCl₂ sprays alone did not control bitter pit on light-cropping, immature trees
• Solubor^TM, Flint^TM, and Messenger^TM in combination with calcium did not further improve bitter pit control
• Appears to be exceptionally susceptible to black rot and white rot, which may be more problematic if cooling after harvest is delayed or warmer storage temperatures of 38 F (3-4 C) are used in order to reduce soft scald
• Especially susceptible to blue mold (Penicillium expansum)
• Tender skin and stiff stems contribute to a high incidence of stem punctures and such fruit are highly likely to develop blue mold when exposed to water- or air-borne P. expansum spores
• Good sanitation is the only approach for minimizing losses to blue mold
• Keep fruit away from bins and storage areas that are contaminated with P. expansum

• Apples should not be run through a postharvest drench treatment because recycling drench water redistributes spores of P. expansum to fruit wounds

Robinson and Watkins

• Fruit from heavy cropped trees are more mature – produced more ethylene, softer, lower acidity, and higher starch ratings
• Fruit from trees with higher crop loads were softer and had higher incidences of soggy breakdown (not soft scald), but also had lower incidences of bitter pit, senescent breakdown, storage rot, and superficial scald
• Crop loads above 10 fruit per cm² of TCA resulted in more poor size, poor color, and poor flavor, which not improve in storage, although they tended to have the least storage disorders
• Moderate crop loads of 7-8 fruit per cm² of TCA resulted in poor return bloom and mediocre fruit quality
• Crop loads around 5 fruit per cm² of trunk cross-sectional area (TCA) appear optimum, resulting in good fruit color and soluble solids, and medium acidity
• Warmer storage temperatures resulted in more bitter pit, senescent breakdown, and storage rot, but less soft scald, soggy breakdown, and superficial scald

For more details, please see the Fall 2003 issue of the NY Fruit Quarterly, available online.

Dr. Chris Watkins will be speaking on February 18^th at the Ontario Fruit and Vegetable Convention at Brock University in St. Catharines during the apple sessions. His presentation in the morning session (10 a.m.) will be ‘Honeycrisp’ – battles with bitter pit, soggy breakdown, and soft scald, while his presentation in the afternoon session (3 p.m.) will be Trials and tribulations with 1-MCP – a New York experience.

Related Links

• New York Fruit Quarterly