Pruning height and selective limb removal affect yield of large 'Hass' avocado trees

Avocado (Persea americana Mill. cv. Hass) trees were pruned over 3 years at either 4 or 6 min height by removing or heading back selected limbs. Yield s were compared with those from control trees with no pruning in the upper canopy. All trees had similar crop loads before pruning. Trees were at 9 x 10-m spacing and were 8 years old when first pruned. Fruit yields were reco rded for 2 years before the first pruning and then in each year of pruning. In the final year, trees were harvested in four height zones: 0-2m; 2-4 in ; 4-6 in; and >6 in. Cumulative yields over 3 years were similar on 6-m and control trees, but were less on 4-m trees due to the large volume of fruit ing canopy removed in the first pruning. The height of the main fruiting zo ne was lowered on the 4-m trees, with yields in the 2-4-m zone similar to t hose in the 4-6-m zone of the control trees. Pruning to reduce the number a nd length of scaffold branches increased fruit yields on the remaining scaf folds without reducing fruit size. Results are discussed in terms of harves t efficiency and the benefits of small tree orchard systems.