Mechanical blossom thinning of ‘Allstar’ peaches influences yield and quality

Peach trees can produce an overabundance of fruit when crop loads are not managed properly, resulting in poor returns due to small fruit size at harvest. Recently, mechanical thinning using string thinners at bloom has been investigated as a method for reducing crop load and labour costs. ‘Allstar’/‘Bailey’ peach trees grown in a supported spindle-type orchard system were subjected to three rates of mechanical blossom thinning (MBT) and hand blossom thinning (HBT) at bloom across two years, with a hand-thinned control added in the second year. Mechanical and hand blossom thinning were both effective in removing flowers and decreasing fruit set with increasing rates. In 2010, only the highest rate of HBT treatment reduced the time needed to hand-thin, but in 2011 nearly all treatments reduced hand thinning labour requirements. Differences in total yield and number of fruit harvested per tree were observed in both years of the study whereas differences in marketable yield were observed only in the first year. The results of this study highlight the benefits of mechanically string thinning peaches at bloom, but also the variability in response across years.