Response of Common Goldenweed (Isocoma coronopifolia) and Buffelgrass (Cenchrus ciliaris) to Fire and Soil-Applied Herbicides

Controlled burning during winter reduced densities of common goldenweed [Isocoma coronopifolia(Gray) Greene] by 33 to 44% and suppressed canopy cover and height of surviving common goldenweeds for 2 yr. Applied to an unburned infestation, 2,4-D [(2,4-dichlorophenoxy) acetic acid] or dicamba (3,6-dichloro-o-anisic acid) granules only partially controlled common goldenweed at rates of 2 kg/ha or less. Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} or picloram (4-amino-3,5,6-trichloropicolinic acid) pellets provided excellent control of common goldenweed if applied at 2 kg/ha during March and at 1 kg/ha if applied after burning in February. The burning pretreatment appeared to synergistically enhance effectiveness of herbicides applied at relatively low rates. Increases in standing crop of buffelgrass (Cenchrus ciliarisL.) following burning were usually small and temporary, but effective herbicide treatments and burn-herbicide combinations increased buffelgrass standing crop by as much as three-fold.