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ARS Home » Pacific West Area » Wenatchee, Washington » Physiology and Pathology of Tree Fruits Research » Research » Publications at this Location » Publication #220415

Title: Preharvest Lipophilic Coatings Reduce Lenticel Breakdown Disorder in 'Gala' Apples

Author
item Curry, Eric
item TORRES, CAROLINE
item NEUBAUER, LUIS

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2008
Publication Date: N/A
Citation: N/A

Interpretive Summary: Since 2000, Lenticel Breakdown (LB) has been a high priority area for research investigations in the arid apple growing regions of the United States. LB usually appears after packing as one or more round, darkened pits on the peel ranging in diameter from 2-8 mm. If symptoms are detected before shipment, there are often significant repacking costs. If undetected, the negative impact on repeat sales can be lasting. Together with Pace International LLC, specialists in development of fruit coatings, ARS evaluated several unique lipophilic formulations to help protect the cuticle during the period of hot arid weather and rapid fruit enlargement that leads to high cuticle microcracking incidence. Emulsions of lipophilic formulation were applied to whole trees at various dosages and timings. LB was assessed after storage at -1 °C for 3 or 6 months. The following season, the best treatment from a single handgun application 7 days before harvest reduced LB after 90 days at -1 °C by 35%, whereas 3 weekly applications beginning 3 weeks before harvest, reduced LB during the same period by as much as 70%. In 2007, the best single treatment applied 1 week before harvest using a commercial airblast sprayer reduced LB by almost 50% after 90 days at -1 °C.

Technical Abstract: Lenticel Breakdown disorder (LB), prevalent on 'Gala' apples, has also been observed on other common cultivars in arid regions. Depending on preharvest environment, fruit maturity at harvest and length of storage, LB usually appears as one or more round, darkened pits, centered on a lenticel, ranging in diameter from 1-8 mm. Symptoms are not visible at harvest nor are they usually apparent on bulk fruit after storage. Following typical fruit processing and packing, however, symptoms are fully expressed after 12-48 h. Our earlier work led to the hypothesis that desiccation stress during the month before harvest was a main causative factor. Thus, several unique lipophilic formulations were developed that might assist the cuticle during this period of hot arid weather and high microcracking incidence due to rapid fruit enlargement. Emulsions of lipophilic formulation were applied to whole trees at various dosages and timings. In 2005, using a single handgun application 1 day before harvest, the best treatment reduced LB by about 20% after 90 days at -1 {degree sign}C. The following season, the best treatment from a single handgun application 7 days before harvest reduced LB after 90 days at -1 {degree sign}C by 35%, whereas 3 weekly applications beginning 3 weeks before harvest, reduced LB during the same period by as much as 70%. In 2007, the best single treatment applied 1 week before harvest using a commercial airblast sprayer reduced LB by almost 50% after 90 days at -1 {degree sign}C.