Eleven herbicides applied in May, were evaluated for yankeeweed control in East-Central Texas. Yankeeweed cover 1 yr later was reduced to 5% or less by 0.28 kg ha-1 of picloram; 0.56 kg ha-1 of clopyralid, glyphosate, or dicamba; 0.28 + 0.84 kg ha-1 of dicamba + 2,4-D, and 1.1 kg ha-1 triclopyr compared with 30% cover in the untreated area. Chlorsulfuron and metsulfuron at 0.07 kg ha-1 reduced yankeeweed cover to 12 and 7%, respectively. Dalapon, 2,4-D, and tebuthiuron were relatively ineffective. Most herbicides, reduced woolly croton cover within 1 mo after treatment compared to the untreated areas, but 2,4-D at 0.28 kg ha-1 and chlorsulfuron at 0.02 kg ha-1 and 0.07 kg ha-1 were most effective after 4 mo. All herbicides, except dalapon at 1.1 kg ha-1 or less and most rates of 2,4-D and tebuthiuron, reduced partridgepea cover during the year of application. Total grass cover was increased 4 and 12 mo following treatment with clopyralid, picloram, dicamba, and triclopyr. On separate sites, bahiagrass and coastal bermudagrass accounted for most of the increased grass cover.

Field studies were conducted in 1984 and 1986 to identify herbicides that would control woolly croton and bitter sneezeweed on grazing land in the Blackland prairies of Texas. Herbicides included chlorsulfuron, clopyralid, dalapon, dicamba, 2,4-D, glyphosate, metsulfuron, picloram, tebuthiuron, 2,4,5-T, and triclopyr. Chlorsulfuron and metsulfuron applied at 0.018 kg ha-1 and 2,4-D, picloram, 2,4,5-T, and triclopyr at 0.28 kg ha-1 controlled >80% of the woolly croton. Metsulfuron controlled more than 90% of the bitter sneezeweed at 0.018 kg ha-1. Similar control was obtained with clopyralid, glyphosate, and picloram each at 0.28 kg ha-1. Bermudagrass cover increased with all herbicide treatments except dalapon at one of three sites.

In field experiments, chlorsulfuron and CGA 131036 did not injure winter wheat. Both herbicides applied postemergence at 9 and 10 g ai/ha completely controlled flixweed. CGA 131036 controlled cutleaf eveningprimrose 81%, and chlorsulfuron controlled 91%. At similar rates, CGA 131036 was also less effective than chlorsulfuron on henbit and Italian ryegrass. Both controlled wild buckwheat 77% when applied postemergence at 18 g/ha. Neither of the sulfonylurea herbicides controlled prostrate spurge or woolly croton as effectively as 2,4-D. In a bean root bioassay, root growth inhibition by both herbicides was partially alleviated by adding isoleucine and valine.

Chlorsulfuron and metsulfuron were effective on Texas whitebrush, killing 70 to 75% of the plants at 0.28 kg ai ha, marginally effective on Macartney rose, killing 15 to 43% of the plants at 1.12 kg ha, but ineffective on honey mesquite and huisache, killing no more than 10% of the plants at 1.12 kg ha. Sulfometuron was ineffective on all woody species at 1.12 kg ai ha. Clopyralid and picloram were effective, killing 70 to 92% of the huisache at 2.24 kg ae ha. Tebuthiuron killed 72% of the Texas whitebrush at 1.12 kg ai ha. Sulfometuron generally reduced herbaceous plant cover the year of application. Chlorsulfuron and metsulfuron often resulted in increased grass cover the year of application. Most herbicides reduced broadleaf weeds the year of application. Woolly croton often was the first prominent broadleaf species to return to areas treated with clopyralid and sulfometuron. Few differences occurred among herbicides in herbaceous weed cover the year following treatment.

Field studies were conducted in 1981 to 1983 to evaluate selected herbicides for control of a natural infestation of woolly croton (Croton capitatus Michx. ♯ CVNCP) in soybean [Glycine max (L.) Merr.]. Ineffective woolly croton control was obtained with all preemergence herbicides evaluated. Early postemergence treatments of acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} and lactofen {1-(carboethoxy)ethyl) 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate} provided excellent woolly croton control. Postdirected applications of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] applied at the V4 stage of soybean growth and tank mixes of cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile}, linuron [N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea], or metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] plus 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] applied at the V4 and repeated at the V6 stage of soybean growth also provided effective control.