Enhanced bud production in highbush blueberry (Vaccinium corymbosum L.) in response to paclobutrazol

Blueberry cultivars were treated with either soil drenches or foliar applications of paclobutrazol. Soil drenches of 25 mg.L-1 inhibited shoot elongation and stimulated earlier and greater flower bud production on 'Bluetta', 'Bluecrop', and 'Jersey'. The treatments increased bud numbers 359% to 797%, and stimulated compound bud formation, while reducing formation of vegetative buds, This resulted in overcropping and reduced fruit size, Foliar applications at concentrations of 5, 10, 50, and 100 mg.L-1 increased bud set. Treatments did not significantly alter time to 50% flowering in 'Bluetrop' or 'Duke', but hastened flowering up to 5 days in 'Blueray' at 200 ppm. Fruit ripening was significantly delayed at 100 and 200 ppm in 'Bluecrop' due to overcropping, but no delays were observed in 'Blueray' or 'Duke'. Plant size and vigor appeared to be a determining factor in plant response. Chemical name used: PP333 or (2RS,3RS)-1(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol (paclobutrazol).