Wyoming Big Sagebrush Control with Metsulfuron and 2,4-D in Northern New Mexico

Abstract

Field experiments conducted between 1982 to 1988 compared 2,4-D [(2,4-dichlorophenoxy)acetic acid] and metsulfuron [2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino)carbonyl]amino]sulfonyl]benzoic acid) for control of Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle and Young) in northern New Mexico. Precipitation was near or above normal during years of herbicide applications. Broadcast sprays of 2,4-D at 2.2 kg/ha were most efficacious during rapid shoot elongation, but mortality averaged less than 38% from treatments applied over 4 separate years. Wyoming big sagebrush shoot growth was greatest in April and May compared to other months, but growth was highly variable among shrubs and probably reduced effectiveness of 2,4-D sprays. The optimum application timing for metsulfuron was during the late-flower growth and fruiting stages. Fall-applied metsulfuron at 0.035 kg/ha provided 65% Wyoming big sagebrush mortality compared to 27% when spring-applied. When metsulfuron was fall-applied at 0.07 kg/ha or higher, control averaged 88% following 3 annual applications. Combining metsulfuron at .0175 kg/ha plus 2,4-D at 1.1 kg/ha was comparable to or more effective than either herbicide applied alone in spring or fall. Total standing crop of grasses increased by nearly 300% after 1 or 2 growing seasons when Wyoming big sagebrush canopy cover was reduced by at least 75% following herbicide treatments.