Evaluation of Herbicides for Phytotoxicity to Rose Plants and Efficacy

Abstract

Abstract Roses frequently occur in gardens and landscapes and may require weed management. Herbicide trials were conducted with 10 herbicides applied at label rates to plots containing a hybrid tea rose cultivar. The primary objective was to evaluate injury to rose plants when herbicides were sprayed over-the-top at two stages of growth: bud break and full leaf. A secondary objective was to evaluate the efficacy of the herbicides. The soil residual (pre-emergent) herbicides Devrinol (napropamide), Goal (oxyfluorfen) and the dinitroaniline herbicides Surflan (oryzalin), Treflan (trifluralin) and Prowl (pendimethalin) did not injure roses when applied at bud break. The herbicides Ornamec (fluazifop-p-butyl), Poast (sethoxy dim) and Envoy (clethodim), which have post-emergent activity, also did not injure roses when applied to roses at bud break or when applied in late spring when plants had fully developed leaves. Roses oversprayed at bud break with the herbicides Roundup (glyphosate) and Trimec Classic (2,4-D + MCPA + dicamba) did not show phytotoxicity symptoms immediately after application but had significantly shorter shoots beginning six weeks after treatment (WAT). Roses with fully developed leaves which were oversprayed with Roundup and Trimec Classic did show symptoms of injury one WAT and thereafter.