Influence of Rootstock on Response of ‘Delicious’ and ‘Golden Delicious’ Trees Treated with Paclobutrazol

Abstract

Mature ‘Golden Delicious’ and ‘Red Prince Delicious’ on seedling, MM.106, MM.111 or M.7 rootstocks were treated with a high or low dosage of paclobutrazol by trunk crown drench in April 1985. Dosage varied with rootstock according to a hypothetical amount of natural growth reduction relative to trees on seedling rootstock. Length of current seasons growth of shoots was measured over the next 4 growing seasons. In the year of application treatment had no effect. The following year, terminal shoot length on both cultivars receiving the higher dosage was significantly less than controls and was controlled to the same degree on all 4 rootstocks. In the second and third years after treatment, differences among rootstocks became more apparent.