INVESTIGATION of Factors Contributing to the DEVELOPMENT of Lenticel Break Down IN ‘Royal Gala' Apples IN SOUTH Africa

Lenticel break (LB) down is a relatively new post harvest disorder observed on apples in apple producing countries world wide.  At present, the actual cause for this disorder is unknown, however there are several factors that possibly contribute towards the observed increase in severity.  Trials were conducted in commercial orchards in the Ceres area with a history of LB to find possible reasons for the development for LB in ‘Royal Gala’.  The possible influence of fruit calcium content and fruit maturity were investigated. Individual fruit analysis to determine whether mineral content influences susceptibility to LB could only be conducted in one season, but showed no correlation between fruit Ca content and LB.  The effect of pre-harvest temperatures, rate of cooling, and storage temperatures and amelioration of orchard conditions were assessed during the past two seasons.  We did not find a simple correlation between minimum or maximum daily temperatures before harvest and LB as was reported in Chile. We also investigated the effect of vapor pressure deficit on the development of the disorder. Very little LB occurred at the experimental sites during 2006/7 and 2007/8.  The storage trials were carried out, and even though statistical differences from the storage results indicated a possible effect of cooling rate, no conclusive results were found due to the low incidence of LB in all trials during 2007 and 2008.