2017 ASHS Annual Conference

We established three replicated trials in Spring 2013 in Mendocino County, California (CA), Hood River, Oregon (OR), and Geneva, New York (NY) to evaluate multiple training system, spacing, and rootstock combinations for the European pear (Pyrus communis) cultivar ‘Bartlett’ (California), ‘D’Anjou’ (Oregon), and ‘Bosc’ (New York): Tall Spindle (TS), “V” Trellis (V-T) , parallel 2-leader (2-L; California only), and nursery-formed Bi-axis (B-A) x 3’, 4.5’ and 6’ spacings x OHxF 69, OHxF 87, and Pyro 2-33 rootstocks (36 total combinations) in a split-split plot design. In California only, an adjacent row of extra B-A and single leader trees was left completely unheaded and unpruned and a replicated sub-trial initiated on one set of the extra B-A trees on OHxF 87 to compare the effect of spreading vs. not spreading on vigor and precocity (remaining trees on OHxF 87 and 69 were left completely unpruned as an unreplicated control. From 2013-2016, TS trees were tallest and also had the largest cultivar single trunk cross-sectional area (TCSA) (B-A trees had the largest total TCSA with both scaffolds combined). TS and V-T and trees were most precocious and efficient. There was a trend for 6’ spacing to have the largest and most fruit. OHxF 87 was the most productive and efficient rootstock and Pyro 2-33 the least. There was a slight trend toward more root suckers in the V-T. For spread versus unspread B-A trees on OHxF 87, there was a trend toward higher yield in unspread versus spread trees, with no difference in fruit size. Spread trees were significantly smaller (shorter) and thus had higher yield efficiency. After four growing seasons, training and rootstock appear to be the most important factors in determining early tree growth and productivity. Tall spindle and V-Trellis are the most productive training systems to date, with V-Trellis having the largest fruit of the two. Spacing has yet to play a discernible role, except (slightly) for tree height. OHxF 87 yield and fruit size exceeds that of OHxF 69 and Pyro 2-33 lags well behind both OHxF rootstocks. V-Trellis has required the least fruit removal to maintain vigor and promote leader development. Pyro 2-33 appears to be slightly more prone to water stress than OHxF 87, perhaps due to its larger canopy size. Spreading of B-A trees appears to reduce vigor, but perhaps also fruiting potential. Completely forgoing pruning in early years appears to encourage early fruiting without compromising tree size (caliper).