ASHS 2015 Annual Conference

Peach trees are traditionally fruit thinned between 30-45 days after full bloom (AFB) to maximize production efficiency and fruit size. Other thinning times and methods are available. In the last few years, peach growers in Georgia have been evaluating the possibility of using bloom thinning in certain varieties. However, the end result and the effect of weather events (i.e. freezes) have not allowed the determination of benefits and/or losses produced by both methods. Bloom thinning can be done during the pink flower and open blossom stages. This method can be more beneficial than fruit thinning resulting in a 10-30% increase in fruit size and yield and a reduction of labor cost needed to thin fruit. The objective of this study was to compare bloom and fruit thinning based on labor use, fruit characteristics, and overall yield. Bloom-, fruit-, and no-thinning treatments were applied to ‘Harvester’ and ‘Redglobe’ peach varieties in 2014. The experimental design was a split plot with a randomized complete block design (RCBD), with plots being the two varieties, seven blocks within a plot, five replicates per treatment (bloom-, fruit-, and no-thinning), and trees as replicates. Bloom thinning was done at full bloom, with a freeze occurring two days after thinning. Fruit thinning was done at 38 AFB. The use of blocks differentiated the effect of the freeze for both orchards, as the blocking corresponded to a gradient in elevation and freeze damage, with one extreme of the experiment having no damage and the other having almost 100% damage. There was a significant difference (P<0.05) for blocks when considering all data together due to the freeze damage, however, the blocks could be separated based on their damage levels. The results hereafter are based on blocks with no freeze damage. Three different harvest time points were performed for ‘Redglobe’ and two harvest points for ‘Harvester’. There were significant differences for the first, third, and total yield harvested when comparing bloom-, fruit-, and no-thinning experiments for ‘Redglobe’ (P<0.05). Similarly, there were differences between the first harvest and total yield when comparing bloom-, fruit-, and no-thinning experiments for ‘Harvester’ (P<0.05). Bloom thinning saved approximately 50% of time of labor per tree when compared to fruit thinning (P<0.05). Differences for fruit weight were observed when comparing bloom-, fruit-, and no-thinning for ‘Redglobe’ (P<0.05). The results of this project yielded encouraging observations; however, this experiment will be repeated due to the environmental effects.