Creosotebush control and forage production in the Chihuahuan and Sonoran deserts

Abstract

Creosotebush (Larrea tridentata [Sesse & Moc. ex DC.] Cov) and other shrubs have spread into semidesert grasslands of the southwestern United States and northern Mexico; and as creosotebush increases, perennial grasses decrease. This study evaluated 3 rates of tebuthiuron and 4 mechanical treatments in 1981 and 1982 for creosotebush control at 4 locations, 3 in Chihuahua, Mexico, and 1 in Arizona, U.S.A., and compared forage production after treatment with untreated checks. Creosotebush mortalities averaged across locations and years were 75, 87, 93, 3, 33, 68, and 68% for the 0.5, 1.0, and 1.5 kg ai/ha tebuthiuron (N-(5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea), land imprinting, 2-way railing, disk plowing, and disk plowing with contour furrowing treatments, respectively. Forage production averaged across locations and years was 529, 524, 606, 303, 344, 290, 330, and 302 kg/ha for the 0.5, 1.0, and 1.5 kg ai/ha tebuthiuron, land imprinting, 2-way railing, disk plowing, disk plowing with furrowing, and untreated check treatments, respectively. Precipitation was below long-term means at all Chihuahuan locations in 1983, and forage production was significantly greater on most treated plots where brush was controlled than on untreated checks. At the Arizona location precipitation was above the long-term mean in 1983 and all plots treated in 1981, except the disk plowing and disk plowing with furrowing which destroyed perennial grasses, produced significantly more grass forage than the untreated checks. Precipitation was above the long-term means at all locations in 1984 and about half of the plots treated with tebuthiuron produced significantly more forage than the untreated checks but not any mechanically treated plots. When treatments reduced shrub density and remnants of native forage grasses were present, forage production increased in both wet and dry years.