Kon, Thomas1; Fernandez, Gina2; Perkins-Veazie, Penelope3; Blaedow, Karen4
1Assistant Professor, NC State University, Mills River, NC, 28759
2Distinguished Professor, NC State University, Raleigh, NC, 27695
3Professor, NC State University, Kannapolis, NC, 28081
4Extension Agent, NC Cooperative Extension, Hendersonville, NC, 28792


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. In response to the labor cost and disease pressure associated with tipping an experiment was initiated in 2019 to to compare effects of primocane growth management strategies on cane architecture, reproductive development, and fruit quality of ‘Prim-Ark Traveler’ blackberry in Mills River, NC.  We investigated the use of a plant growth regulator, prohexadione calcium (P-Ca), as an alternative primocane growth management strategy for primocane-fruiting blackberry. Treatments consisted of an untreated control, tipping at 46 cm and 91 cm or three applications of 200 ppm P-Ca + 0.125% (v:v) non-ionic surfactant. Visible effects of P-Ca on primocane height were apparent within 14 days of the initial application and a significant reduction in height (25% reduction) was observed 21 days after treatment. Cumulative, marketable, and cull yield did not differ among treatments. Results from the study showed that P-Ca has promise as an alternative to reduce primocane height, but this practice would likely need to be augmented with additional practices to enhance fruiting lateral number and subsequent productivity if it is to be a commercially viable option. Future research will focus on addressing specific P-Ca application timings, alternative plant growth regulators, and cultural practices to assist with managing season long vegetative growth while increasing yields.


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