Effect of training system and rootstock on growth and productivity of Golden Russet® Bosc pear trees

Interest in size controlling, precocious rootstocks has precipitated increased sales of trees grafted to the 'Old Home' x 'Farmingdale' (OHxF) series (Brooks selections). A replicated trial was established in a commercial orchard in Lake County to evaluate performance of 'Golden Russet® Bosc' on six rootstocks and five training systems. Trees grafted on OHxF 69, 97, 217, 333, and 513, and P. Betulaefolia were planted in May 1993. Spacing was 5 x 3 m (797 trees/ha) for the central leader, three-leader, and parallel hedgerow (grower system) training systems. Spacing was 5 x 1.5 m (1,594 trees/ha) for the freestanding perpendicular fan and Tatura trellis systems. The Tatura was formed by heading single trees at planting, rather than double planting. Four systems received delayed heading, pinching of upright and narrow angle young shoots, selective limb tying and summer pruning. The parallel hedgerow was exclusively dormant pruned by the grower and received intensive limb tying through the season. Final height of free standing trees was approximately 4.5 - 4.7 m. Tatura trellis height was limited to 3 m to maximize sunlight penetration and avoid use of ladders. No fruit thinning was done prior to harvest. Trunk circumference and tree height were measured from 1994 - 1999. Yield per tree and fruit size were measured from 1996 - 1999 and yield per hectare, yield efficiency, and economic return calculated. The Tatura had the highest total gross cumulative returns per hectare. The most productive systems on a per tree basis, factoring in spacing, were the parallel hedgerow and central leader. The three-leader and perpendicular fan systems were least productive on a per hectare, and the perpendicular fan on a per tree basis. OHxF 69 was the most productive rootstock and OHxF 513 the least. The combination of Tatura trellis/OHxF 69 yielded the highest cumulative returns. Results indicate that the Tatura must be combined with the correct rootstock as productivity of training/rootstock combinations varied widely. Row spacing is critical since results would have differed if spacing had been adjusted for the shorter height of the trellis, thus increasing number of trees per hectare by one-third. Tatura returns were reduced in 1998 due to small fruit size, indicating fruit thinning is needed in heavy cropping years. Major drawbacks related to installing a Tatura trellis in California are cost of additional trees, cost of trellis installation, and risk of inadequate lateral shoot growth (as is a tendency with 'Bosc'). Major benefits include earlier cash flow, more efficient labor, reduced labor insurance costs, and improved pesticide deposition.