Published online by Cambridge University Press: 12 June 2017
Picloram (4-amino-3,5,6-trichloropicolinic acid) and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} were the most effective herbicides for killing Macartney rose (Rosa bracteata Wendl.) on the Claypan Resource Area of Texas. At 4.5 kg/ha picloram (ae/ha) and tebuthiuron (ai/ha) as sprays killed 70% of the plants and as pellets 73 and 84% 1 yr after application, respectively. Bay Met 1486 {N-[5-(ethylsulfonyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone}, 2,4-D [(2,4-dichlorophenoxy) acetic acid], 3,6-dichloropicolinic acid, glyphosate [N-(phosphonomethyl)glycine], hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione], and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid} were markedly less effective than either picloram or tebuthiuron. After 2 to 4 months, 2,4-D, picloram, picloram + 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and triclopyr reduced the Macartney rose canopy by at least 95%, but only picloram and tebuthiuron controlled Macartney rose after 3 yr. Sprays of glyphosate and hexazinone inhibited growth of grasses after 3 months. Most herbicide sprays reduced broadleaf cover for at least 3 months.