Growth retarding effects of paclobutrazol and RSW 0411 on Granny Smith and Fuji apple trees

Abstract

. The growth retardants paclobutrazol (3-[(4-chlorophenyl)methyl]-a-(1,1-dimethylethyl)-IH-1,2,4-triazole-l-ethanol)and RSW 0411 ((3-(cyclohexyl methylene)-a-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol) were tested on two-year-old trees of Granny Smith and Fuji apple . RSW 0411 at 100 mg/L did not cause any growth reduction in Granny Smith, while 500 and 1000 mg/L significantly reduced growth below that of the control between 27 and 40 days after application . Paclobutrazol at 100 mg/L had a small effect on growth of Granny Smith shoots ; however 500 mg/L significantly reduced shoot growth between 27 and 55 days after application, and 1000 mg/L reduced shoot growth between 27 and 82 days after application . By 100 days after application, there were no longer differences between treatments . Shoot growth on Fuji trees was reduced below that of the control as follows : between 14 and 27 days following a single application of 500 mg/L RSW 0411 ; between 27 and 55 days following two applications ; between 14 and 72 days following three applications ; and between 14 and 82 days following four applications . Treatments were applied 14 days apart . Paclobutrazol was a more active growth retardant than RSW 0411 at the same rate, and the growth-retarding effects of RSW 0411 were short-lived .In recent years, trees in many New Zealand apple orchards have been planted intensively ; 3-5 m between rows and 1-3 m within rows . In Europe, most trees at these spacings are planted on the dwarfing M 9 or M 26 rootstocks ; however, in New Zealand, trees continue to be planted on the semi-dwarfing MM 106 rootstock .Growers and advisors thought that height and spread of trees on MM 106, at close spacings, would be adequately controlled through early cropping . How-

Paclobutrazol Boost up for Fruit Production: A review

“…However, the eff ectiveness of PP333 varied with the dose, time, and method of application. Irving and Pallesen [30], found that on twoyear-old apple 1000 ppm of PP333 had extraordinarily little eff ect on vegetative growth and remained eff ective up to 82 days of application. But Stinchcombe, et al [31], reported that, in Cider apple, PP333 at 2000 ppm remained eff ective in the following year also.…”