Unravelling cherry slip-skin maceration disorder

Cherry slip-skin is a problem affecting the health and quality of primarily, late season sweet cherry (Prunus avium L.). Reports of this condition causing major problems in the 2012 harvest came from both British Columbia and Washington State producers, with significant but variable incidence in following years. Previously in the literature slip-skin maceration disorder has been described as a post-harvest disease caused primarily by Rhizopus arrhizus Fischer and R. stolonifer (Ehrenb. ex Fr.) Lind in French prunes and Mucor piriformis A.Fisch., in cherries. Preliminary investigations reported here differ somewhat and suggest both physiological and pathological components, involving several different yeast species within the genera Hanseniaspora, Aureobasidium, Cryptococus, Candida and Rhodotorula. The condition is not easily visible until just after harvest and may not show up until after shipping. Following harvest, the shoulder of the cherry becomes noticeably soft and the skin disassociates from the inner tissue which has become macerated. With time, while the rest of the cherry remains firm, the affected tissue develop radially causing breakage of the skin and during shipping the affected areas may form sunken craters on the fruit’s surface. In this current study, trials involving canopy management and early season calcium sprays have both produced improvements in fruit health: 20% and 60% respectively. Fungicide trials conducted in a research cherry block (cv. Staccato) identified several products, Oxidate® 2.0 and Tilt® 250E, that reduced cherry slip-skin development by 70% and 51% respectively, while other products such as potassium meta-bisulphite only reduced symptoms by 18% and Quintec® which showed a slight increase when compared to controls.