THE USE OF BIOREGULATORS IN THE PRODUCTION OF DECIDUOUS FRUIT TREES

Development of branched trees in the deciduous tree-fruit nursery has become more important as availability of size-controlling rootstocks has made higher-density plantings commercially feasible. Although European and North American nursery tree production practices differ in some respects, both require the use of appropriate bioregulator products for the effective induction of lateral branches in many fruit-tree cultivars. Among the many bioregulator products tested over the past half century, products containing cytokinins (e.g., 6-benzyladenine) with or without gibberellic acid isomers (usually a mixture of GA₄₊₇) have proven the most useful for producing good quality feathered nursery trees. The demand for well-feathered nursery trees is stronger in Europe but is growing in North America. A new bioregulator, cyclanilide® (CYC, Bayer Environmental Science, 95 Chestnut Ridge Rd., Montvale, N.J. 07645), has been tested for growth-related effects on nursery apple (Malus × domestica), pear (Pyrus communis) and sweet cherry (Prunus avium) trees. CYC treatment of difficult-to-branch cultivars such as ‘Cameo’ apple or ‘Bing’ sweet cherry trees in the nursery increased the formation of well-developed feathers up to 6-fold and with minor or no effect on caliper or final tree height. CYC appears promising for lateral branch induction in nursery fruit trees.