Managing vigor of blackberry with prohexadione calcium: effects on primocane and floricane development
In the southeastern United States, primocane growth management of blackberry relies on summer pruning/tipping primocanes at multiple heights throughout the growing season. Tipping increases the risk of cane blight infection (Leptosphaeria coniothyrium) and is both labor intensive and expensive. Alternative strategies to manage primocane growth of blackberry are not available. We investigated the use of a plant growth regulator, prohexadione calcium (P-Ca), as an alternative primocane growth management strategy for blackberry. In 2018, an experiment was initiated in a two-year-old planting of Osage and Von at 0.9×3.7 m spacing. Treatments consisted of an untreated control, or three applications of 200 ppm P-Ca + 0.125% (v:v) non-ionic surfactant. Treatments were applied to 24 uniform two-plant plots (12 plots per cultivar). The experiment was replicated six times, had a split-plot design, and analysis of variance was performed to test main effects and interactions. The first P-Ca application was applied when primocanes were 43 cm tall followed by applications at ~21 d intervals. In both cultivars, three applications of 200 ppm P-Ca reduced primocane height by 25% and internodal length by 38% when compared to the control. In general, P-Ca did not have negative effects on yield and fruit quality in the year of treatment. Initial results appear promising and the experiment will be repeated in 2019. Identical treatments will be applied to the same plots to determine effects of multi-season P-Ca applications on primocane and floricane development.
Kon, T.M., Fernandez, G.E., Perkins-Veazie, P. and Blaedow, K. (2020). Managing vigor of blackberry with prohexadione calcium: effects on primocane and floricane development. Acta Hortic. 1277, 329-336
Rubus, growth retardant, plant growth regulator, vegetative growth, internode