Effects of cultar (Paclobutrazol) on vegetative growth and fruit production by nashi (pyrus serotina rehd)

Abstract

Paclobutrazol was applied to 2-year-old nashi trees either as a soil drench or as a series of four post-flowering foliar sprays, at a low and a high rate of 0.5 and 1.0 g a.i. per tree or 125 and 250 ppm, respectively. The cultivars treated were ‘Hosui’, ‘Kosui’, ‘Nijisseiki’, and ‘Shinsui’. All cultivars showed a significant reduction in vegetative growth within the first season and for up to 4 years after initial application. Most reduction in growth was obtained from soil applications. Least reduction in growth was from a foliar application at the lower rate of 125 ppm. Greatest reduction in growth was obtained with ‘Kosui’, and least with ‘Hosui’. Over the period of the trial, total fruit numbers and yield, per tree, were reduced by paclobutrazol application, though average fruit size was generally increased from Year 2 onwards. With ‘Hosui’, soil applications of paclobutrazol caused a significant increase in levels of the “bud jump” floral bud disorder and consequently a serious reduction in fruit production. Treatment with paclobutrazol generally reduced the percentage of growth extending beyond the top of the Tatura trellis training system, out of reach from the ground. Soil treatment of ‘Hosui’, and foliar treatment of ‘Kosui’, also produced a more even distribution of flowers and fruit throughout the canopy. © Crown copyright 1991.