Printer friendly .pdf file - Horticulture - Cornell University

2Honeycrisp – some preliminary observationsHoneycrisp is a new apple variety forNew York that has created lots of marketenthusiasm. However, problems with this varietycould destroy market confidence for the apple.The most important postharvest problems arebitter pit and soft scald.Bitter pit generally is thought to berelated to calcium concentrations in the fruit. Itsincidence is often worse in younger, vigorouslygrowing trees than in mature, evenly croppingtrees. Therefore, a combination of preharvestcalcium sprays together with good orchardmanagement will likely result in satisfactorycontrol of pit. We are currently investigating theeffectiveness of calcium sprays for pit controland initial results should be available by spring.Soft scald, however, has been of greaterconcern because its appearance in the marketplace has been sporadic. Also, the problem issometimes expressed as an internal browningthat is not apparent on the outside of the fruit. Inthe 1999 harvest season, we carried out our firsttrials with Honeycrisp. We focussed on theeffects of:1. Temperature, because soft scald may be achilling-injury, and therefore controlled byraising the storage temperature;2. Diphenylamine (DPA) application, becausethis antioxidant compound, when used forcontrol of superficial scald, has beeneffective for control of soft scald in othervarieties;3. Delays before storing fruit at low storagetemperatures, as sometimes this can controlthe disorder.Fruit were harvested in a Western New Yorkorchard on September 17, 1999, and treated asdescribed in Table 1.Soft scald was reduced by storing fruit at36 o F compared with 33 o F, and by treatment offruit with DPA at harvest, but these reductions inincidence, while significant, did not eliminate thedisorder. In contrast, a delay of a week at 50 o Fprior to either 33 or 36 o F storage markedlyreduced soft scald incidence, overall averaging0.6% compared with 19% in the non-delaytreatments. Factors such as firmness and solublesolids were not affected by treatment, but theaverage bitter pit incidence of fruit subjected to adelayed cooling treatment was 25% comparedwith 14% in the non-delay treatment. Therefore,use of delayed cooling treatments should be usedonly on fruit with a low bitter pit risk.Table 1: Soft scald incidence in Honeycrisp fruituntreated or treated at harvest with 1000ppmDPA, and then stored at 33 o or 37 o F, or kept at50 o F for one week before being stored at 33 o or36 o F.TreatmentSoft Scald(%)Stored at 33 o F28aStored at 36 o F19bDPA-treated, stored at 33 o F 19bDPA-treated, stored at 36 o F 8cOne week at 50 o F, then stored at 2cd33 o FOne week at 50 o F, then stored at 0d36 o FDPA-treated, one week at 50 o F, 0dthen stored at 33 o FDPA-treated, one week at 50 o F, 0dthen stored at 36 o FValues with different letters indicatedifferences between means at the 5% level.We were reluctant to make recommendationsfor use of delay treatments for control ofsoft scald based on one year of data. However,trials performed in 2000 have confirmed theseresults, and informal tasting of the fruit does notsuggest that Honeycrisp quality is affected bydelayed cooling treatments. Also, at least twogrowers have tried this or similar methods withgood results. Therefore, a tentativerecommendation is made that a short delay,either at 50 o F or in a barn at similartemperatures, before cold storage might be worthtrying. In the longer term, however, storagetemperature control, perhaps 38-40 o F, may be abetter solution, at least for early to mid-harvestedfruit. This year’s research, which is still inprogress, suggests that a higher storagetemperature is less effective for late harvestedfruit than early harvested fruit. Furtherrecommendations will be made available to theindustry before the 2001 harvest.