Dikegulac Sodium Concentration and Application Number Affects Branching of Blackgum and Southern Sugar Maple during Container Production

Abstract

A study was conducted under nursery production conditions to evaluate multiple concentrations of dikegulac sodium (dikegulac) (0, 800, and 1,600 ppm) applied either once or twice as a foliar spray to blackgum grown at two locations in Alabama and to southern sugar maple grown at a single location. Mid-season and end-of-season shoot counts increased linearly in response to increasing dikegulac concentrations in both species and at both locations. Shoot counts also were greater when dikegulac was applied twice compared to a single application, except when 800 ppm dikegulac was applied to blackgum at one location. Both southern sugar maple and blackgum were visibly more branched and compact following treatments with dikegulac than nontreated control plants, although the branching response was much greater in blackgum. Effects of dikegulac application on plant height and caliper varied with species, concentration, application number, and time after application. Southern sugar maple exhibited temporary reddening of immature foliage that dissipated over time, while immature foliage of blackgum yellowed at one location and cupped and developed necrotic lesions at the second location. No phytotoxicity was evident 6 weeks after dikegulac application.