Developing thinning programs for European pear

As there is little information available on chemical thinning programs for European pears or on the effect of chemical thinning agents on pear fruit quality, the work described here was undertaken to examine chemical thinning options for European pear and to develop the most viable options into practical programs. The cultivar 'Packhams Triumph' (Packham) was used in these studies. Chemicals examined included ethephon, ammonium thiosulphate (ATS) and potassium thiosulphate (KTS) applied during the flowering period and 6-benzyladenine (BA) applied as a post-bloom thinner. The desiccating agent ATS was an effective blossom thinner, and two applications at 20% and 50% bloom stage would be recommended. KTS also showed potential as a blossom thinner. BA proved to be a consistent thinner of Packham, and can be applied as early as 10 dAFB to as late as 40 dAFB following a blossom application of either ethephon or ATS. All chemicals examined maintained or improved fruit quality measured as size, firmness and sugar content, but ATS caused a slight increase in skin russet. This work has resulted in practical recommendations for the use of a range of chemical thinning agents to manage crop load in Packham pear.