DETERMINING FIELD RECOMMENDATIONS FOR CONTROL OF SAND BLACKBERRY WITHTRICLOPYR

Triclopyr ([3,5-6-trichloro-2-pyridinyl] oxyacetic acid) rates, month of application, spray volumes, propellant pressures, and use of an adj uvant were compared in four south-central Florida trials for control o f sand blackberry (Rubus cuneifolius Pursh) in pasture. Fluroxypyr (4- amino-3,5-dichloro-6-fluoro-2-pyridyloxyacetic acid) and dicamba (3,6- dichloro-2-methoxybenzoic acid) were included in one trial. Total nons tructural carbohydrate (TNC) concentrations in rhizomes were determine d in samples collected at 28-d intervals. Triclopyr at 0.5 lb (ai) acr e-1 reduced (P < 0.05) blackberry cover from an average 76% pretreatme nt to 18% at 1-yr posttreatment, which was not different from 9% cover with 2.0 lb acre-1 triclopyr. Triclopyr at 0.5 or 1.0 lb acre-1 appli ed in April or May (spring) did not reduce cover compared to those rat es in September (fall) (21% vs 23%). Rhizome TNC concentration followe d a cubic response (P < 0.001) to sample date (11% min. April to 27% m ax. October). Increasing pressure alone from 40 to 86 psi, or increasi ng pressure together with an increase in spray volume from 40 to 60 gp a for 0.5 and 1.0 lb acre-1 triclopyr did not decrease blackberry cove r. Applying 0.5 lb acre-1 of triclopyr in spring and fall (1.0 lb acre -1 total) reduced cover (4%) below that from 1.0 lb acre-1 applied onc e in either spring (26%) or fall (44%) in one trial, but not in a seco nd trial. Use of an adjuvant with 0.5 or 1.0 lb acre-1 triclopyr did n ot reduce blackberry cover. Increasing fluroxypyr from 0.25 to 1.0 lb acre-1 decreased cover from 23% to 1%. Triclopyr at 0.5 lb acre-1 had less cover (18%) than the control at 1-yr posttreatment (79%), but dic amba at 1.0 lb acre-1 applied in spring and fall (total 2.0 lb acre-1) was not different (66%) from the control. No treatment eliminated bla ckberry, but 0.5 lb acre-1 of triclopyr applied in spring at 40 gpa wi th 40 psi provided an average 58% reduction in cover 1-yr posttreatmen t.