Abstract

Sweet cherry rain cracking can be a devastating event that reduces yield and negatively affect profitability in cherry (Prunus avium L.) production worldwide. Although not exclusively, cracking usually occurs after a rain event close to harvest. Osmotic potential differential between the fruit and rain water deposited on its surface is believed to be responsible for most rain-related cracking. Different cultivars have different susceptibility to this physical-physiological disorder. This disparity is thought to be caused by differences in their cuticle structure and development (presence of micro-cracks) and epidermal thickness. One of the most common preventive measures is preventing rain water to get in contact with the fruit cuticle. This can be done by covering the trees, blowing rain water from the fruit's surface using airblast sprayers or helicopters, applying calcium right before and during rain events, and chemical treatments with lipophilic protectants. Lipophilic/hydrophobic coating (currently named RainGard T, Pace International, LLC) applied as a program during the last stage of fruit growth has been tested in several commercial orchards and cultivars located in the VII and VIII Region of Chile since 2004. The lipophilic material reduced fruit cracking on average 40.5, 40, and 52% in 'Bing', 'Sweet Heart', and 'Van', respectively. Cracking reduction efficacy was further increased when RainGard T was combined with CaCl2. Overall, no significant treatment effects were found over fruit size, soluble solids content, firmness, skin color, and fruit pitting incidence. The application program had no significant effects over leaf photosynthesis, photosynthetic efficiency, transpiration or chlorophyll content.