Growth and Fruiting of ‘Heritage’ Primocane Fruiting Red Raspberry in Response to Paclobutrazol

Abstract

Abstract Paclobutrazol (PP333) was applied to dormant ‘Heritage’ primocane fruiting red raspberry (Rubus idaeus L.) plants at dosages of 0, 6, 12, 24, 48, and 96 mg a.i.·0.37 m−2 ·hill−1. After 29 days of fruit production, the average cumulative fruit yield of primocanes treated with 24, 48, or 96 mg of paclobutrazol was 92% greater than for control primocanes. The cumulative fruit yield of primocanes receiving the 24-mg dosage remained significantly greater through 50 days of production compared to that of control primocanes. Cumulative fruit yield was not adversely affected at any time during the production season by any of the dosages applied. The 24-mg dosage suppressed final primocane height by 19% but did not significantly decrease primocane diameter or the number of nodes formed. The vegetative responses to 48- and 96-mg dosages were similar, with an average reduction in primocane height, diameter, and total number of nodes formed of 36%, 25%, and 14%, respectively. Early onset of anthesis was positively correlated (r = 0.72) with suppression of vegetative growth. Production midpoint occurred 60 ± 3.7 days after initial anthesis and varied (r = 0.85) with the date of first anthesis. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).