Abstract/Contents: | "Kochia (Kochia scoparia L.) poses a threat to roadside management programs, especially in bareground settings. This species thrives in roadside and other harsh environments. Kochia has widespread resistance to sulfometuron and is beginning to show resistance to diuron. Several diuron alternatives were evaluated for early-season activity against kochia, and in a separate experiment, postemergence kochia control was assessed for fifteen non-crop herbicides. In May 2007, trials were established in right-of-way settings in State College and Enola, PA to compare early-season activity among herbicide mixtures containing sulfometuron plus chlorsulfuron at 0.16 and 0.079 kg/ha, respectively, either alone, or combined with 7.2 kg/ha diuron, 0.28 kg/ha flumioxazin, 4.5 kg/ha pendimethalin, 1.1 kg/ha prodiamine, or 0.42 kg/ha sulfentrazone. Glyphosate at 1.7 kg ae/ha was applied alone and included with the other herbicide treatments. The experiment was repeated at a roadside location in State College, PA in May 2008, with the additional treatment of bromacil plus diuron at 3.6 plus 3.6 kg/ha. In July 2008, postemergence kochia control was compared at sites in Bellefonte and Jersey Shore, PA, using the following herbicides (in kg ae/ha): 2.4-D at 2.1, aminocyclopyrachlor at 0.056, aminopyralid at 0.070, clopyralid at 0.11, dicamba at 0.84, dicamba plus diflufenzopyr at 0.14 plus 0.056, fluroxypyr at 0.21, glyphosate at 1.7, hexazinone at 1.1, imazapic at 0.21, imazapyr at 0.28, metsulfuron at 0.042, triclopyr at 0.84, saflufenacil at 0.098, and sulfometuron plus metsulfuron at 0.11 plus 0.042. Results from the early season trials were variable, possibly due to differences in kochia size and vigor at time of treatment. At State College in 2007, larger kochia plants, approximately 15 cm tall, were not eliminated by the glyphosate component as intended and were released. Treatment effect was not significant in the analysis of variance, but an orthogonal contrast comparing kochia cover in sulfentrazone-treated plots (2 percent) to the other herbicide treatments (33 to 78 percent) was significant. Differences in kochia cover were not significant at Enola, although kochia was less vigorous with 25 percent cover in untreated plots at season end. At State College in 2008, treatments containing sulfometuron plus metsulfuron combined with either diuron, flumioxazin, pendimethalin, prodiamine, or sulfentrazone, and the bromacil plus diuron treatment were rated significantly lower for kochia cover (2 to 23 percent) than sulfometuron plus metsulfuron alone (48 percent) at the end of the trial. Postemergence kochia control also appeared to vary with plant size and vigor. Significant differences in injury and control ratings at the poor-quality, low vigor Jersey Shore site did not translate into differences in percent kochia cover. Kochia was more vigorous at the Bellefonte site, with some plants as tall as 1.3 m at time of treatment. Dicamba, glyphosate, dicamba plus diflufenzopyr, fluroxypyr, and 2,4-D provided significant reduction in kochia cover compared to the untreated plots." |