C.R. Unrath

Suppression of apple bloom with gibberellin sprays

SummaryGibberellin A4+7 at concentrations of 250 mg P1 active ingredient (a.i.) or less, applied as one, two or three sprays 4-16 weeks after petal fall gave inconsistent flower thinning on five year old redchief ‘Delicious’ apple trees. Four sprays, each a month apart, beginning one month after petal fall on similar six year old trees, with concentrations of 250 or 500 mg r1 a.i., eliminated 95% or 99% of return bloom, respectively.

Growth dynamics of young apple trees as influenced by scion and rootstock vigour

Growth of young potted apple trees composed of ‘Classic Delicious’ (nonspur) or ‘Red- chief Delicious’ (spur-type) scions grafted onto O.P. Malus domestica L. (seedling) or Mailing 26 (M.26) rootstocks was observed during three growing seasons. Across rootstocks, spur-type ‘Delicious’ characteristics include lower whole-tree and shoot-wood dry weights, resulting in higher root/shoot ratios. Across scions, rootstock had little effect on dry weight of tree parts above the graft union, whole-tree dry weight or spur density. Trees on M.26 dwarfing rootstock had higher root shank and lower fibrous-root dry weights on all three sampling dates. Although few scion by rootstock interactions were detected, the spur-type scion on M.26 had the most spurs and flowers per metre of scion by the third growing season.