Preemergent herbicide phytotoxicity was evaluated for six species of container-grown ornamental grasses: beach grass (Ammophila breviligulata Fern.), pampas grass [Cortaderia selloana (Schult. & Schult. f.) Asch. & Graebn.], tufted hair grass [Deschampsia caespitosa (L.) Beauvois.], blue fescue [Festuca ovina cv. glauca (Lam.) W.D.J. Koch], fountain grass [Pennisetum setaceum (Forssk.) Chiov.], and ribbon grass (Phalaris arundinacea cv. picta L.). Herbicides included isoxaben, metolachlor, MON 15151, napropamide, oryzalin, oxadiazon, pendimethalin, prodiamine, and trifluralin; the granular combination products of benefin plus trifluralin; and oxyfluorfen plus pendimethalin. Metolachlor, granular or spray, and oryzalin severely injured all species tested, except beachgrass, which was not injured by metolachlor granule. Napropamide injured pampas grass, fountain, grass, blue fescue, and tufted hair grass, but was safe on ribbon grass and beach grass. Pendimethalin, prodiamine, trifluralin; MON 15151, isoxaben, oxyfluorfen plus pendimethalin, and benefin plus trifluralin were safe on all six species. Chemical names used: N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine(benefin);N-[3-(1-ethyl-1-methylpropyl)5-isoxazolyl]-2,6-dimethoxybenzamide(isoxaben);2-chloro-N-(2-ethyl-6-methylphenyll-N-(2-methoxy-1-methylethyl)acetamide (metolachlor); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate(MON 15151);N,N-diethyl-2-(l-naphthalenyloxy)propanamide (napropamide); 4-(dipropylamino)-3,5-dinitro-benzenesulfonamide (oryzalin); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (oxyfluorfen); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin); N3,N3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine (trifluralin).
For the past 5 years, we have evaluated more than 100 herbaceous perennial groundcovers, including both grasses and grass mixtures, as well as ornamental broadleaf materials, for their ability to establish, suppress weeds, provide aesthetic appeal, and resist pests in various landscape and roadside settings across New York State. By working in cooperation with the NYSDOT, we have developed recommendations for materials that have performed well in difficult, potentially stressful, roadside and landscape settings. We have performed replicated research and demonstration trials that have clearly shown that certain species and cultivars provide effective weed suppression; great aesthetic appeal due to foliar texture, color, or flowering, resist pests and diseases; and require low maintenance over time. In addition, certain materials tolerate high levels of salt (NaCl), simulating roadside salt application exposure, in supplemental greenhouse studies. Materials generally suppressed weeds effectively by forming a dense canopy in a short period of time, and reducing light interception at the soil surface under this dense canopy. Certain groundcovers also appeared to exhibit strong potential allelopathic properties when grown either in field or laboratory settings. The selection of new plant materials for use in low-maintenance landscape settings offers potential to reduce time and maintenance inputs in difficult landscape or roadside settings, with the added benefit of reducing pesticide application in these settings for weed management. Additional studies are currently underway to develop further recommendations for use of warm- and cool-season turfgrasses in these settings.
Several juniper species and cultivars were compared for sensitivity to labeled and experimental postemergence graminicides. The junipers treated were: Juniperus horizontalis Moench. ‘Wiltonii’ (blue rug), J. h. ‘Bar Harbor’ (Bar Harbor)), J. h. ‘Youngstown’ (Youngstown Andorra), J. chinensis L. ‘Pfitzeriana’ (Pfitzer), J. c. ‘Parsonii’ (Parson’s), J. c. ‘Sargentii’ (Sargent’s), and J. conferta Parl, (shore). The herbicide treatments were fluazifop-p, sethoxydim, haloxyfop, quizalofop, cycloxydim, and fenoxaprop at recommended rates for annual grassy weed control, with recommended spray adjuvants. ‘Bar Harbor’ juniper was injured, in decreasing order of severity, by haloxyfop, fenoxaprop, quizalofop, and fluazifop. Sethoxydim and cycloxydim produced no reduction in plant fresh weight for the juniper cultivars tested. However, sethoxydim plus adjuvants did reduce ‘Bar Harbor’ juniper visual quality ratings in 1986. Pfitzer juniper was slightly injured by haloxyfop in 1985 and by fenoxaprop in 1986. The other junipers were unaffected by herbicide treatments. Chemical names used: (R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy] phenoxy] propanoic acid (fluazifop-p), (±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy] propanoic acid (fenoxaprop), 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid (haloxyfop), (±)-2[-4-[(6-chloro-2-quinoxalinyl)oxy]phenoxy] propanic acid (quizalofop), 2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one (sethoxydim), and 2-[1-(ethoxyimino)butyl]-3-hydroxy-5-(2H-tetrahydrothiopyran-3-yl)-2-cyclohexen-1-one (cycloxydim).