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Investigation of pruning strategies for dried plums including hand, mechanical and combinations

Krueger, W.H., Niederholzer, F.J.A., Fichtner, E.
Acta horticulturae 2013 no.985 pp. 201-207
Prunus domestica, adverse effects, alternate bearing, canopy, fruit yield, growers, labor, ladders, mechanization, plums, prunes, saws, summer, topping (pruning), trees
Dried plum (Prunus domestica) trees are pruned to thin fruitwood, improve fruit size, reduce alternate bearing and control tree size and shape. Hand pruning with ladders and loppers has long been thought to be the best alternative for pruning because of the selective nature of the pruning which cannot be matched by mechanical pruning. Because of the increasing cost and decreasing availability of labor, growers have continued to look for strategies to reduce pruning costs while maintaining yield and quality. A four year study in Glenn County (Sacramento Valley) and a two year study in Tulare County (San Joaquin Valley) compared the traditional hand pruning during the dormant season using ladders and hand shears to various combinations and timings of mechanical hedging and topping combined with a less detailed pruning from the ground using pneumatic pruners, pole saws and/or long handled shears without ladders. In both studies the mechanical pruning treatments included dormant or post-harvest topping and a "V" cut where the center of the canopy was mechanically shaped into a V. In the Glenn County study the mechanical pruning treatments also included a "roof top" treatment and summer timings of the mechanical treatments. Cumulative yields and value per ha for the 4 years of the Glenn County study were significantly higher for all of the mechanical plus ground pruning treatments than the traditional hand pruning utilizing ladders and shears, suggesting that the hand pruned treatments may have been over pruned. In the Tulare study neither fresh nor dry yield was affected by pruning treatment in either year. The results from both locations suggest that mechanized pruning techniques may be employed in combination with less-detailed hand pruning from the ground, without adverse effect on yield or fruit size.