Preharvest Programs to Reduce Lenticel Breakdown In Apples

Lenticel-related disorders in apple have been a concern for most growers and packers in Washington since the late 1990s. In a survey conducted in the 2005/06 storage season, we found that half of the packers contacted reported lenticel-related problems such as lenticel breakdown and lenticel blotch pit. The post harvest manifestation of these disorders has resulted in signifcant losses – up to 30% of a storage room/orchard block/year. Cultivars most affected include Gala and Fuji. Since 2006, the Washington Tree Fruit Research Commission has facilitated testing of promising approaches utilizing hydrophobic spray emulsions applied preharvest to mitigate lenticel breakdown. Trials in commercial Washington orchards tested Raynox, soybean oil, summer supreme oil, SylGard, SylTec, and EpiShield using different concentrations and timings. All fruit were harvested at commercial maturity suitable for long term CA storage. We found no differences for common maturity parameters at harvest or after storage between control and treated fruit. Fruit from multiple sites expressed symptoms after 3 and 6 months of CA storage similarly. No significant treatment effect was seen regarding oil type or spray frequency. 2008/09 trials are in storage and results will be discussed. It appears, lenticel breakdown problems are best mitigated by harvest at optimum maturity and careful postharvest handling.