Response of three shrub communities in southeastern Idaho to spring-applied tebuthiuron

Abstract

Tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-61]-N,N′-dimethylurea) pellets containing 20 and 40% active ingredient were applied at 0.6 and 1.1 kg ha-1 during May 1979 to range sites dominated by mountain big sagebrush (Artemisia tridentata subsp. vaseyana Nutt.), threetip sagebrush (A. tripartita Rydb.), and gray horsebrush (Tetradymia canescens DC) to determine effectiveness for shrub control and response of associated grasses and forbs. Sagebrush densities were significantly less (P is lesser than or equal to .05) in 1984 on all herbicide treated sites compared to the untreated sites. The 1.1 kg ha-1 (20P) treatment reduced the densities of all shrubs more than other treatments at all sites. Grass production was significantly (P is lesser than or equal to .05) greater on plots treated at 1.1 kg ha-1 (40P) at the mountain big sagebrush and threetip sagebrush sites. Forb production did not respond to tebuthiuron treatments. Grass production was not increased or decreased significantly by any treatment at the gray horsebrush site. For sites with similar soil and environmental conditions, the 1.1 kg ha-1 (40P) treatment should give sufficient control of sagebrush to allow for significant increases in total grass and forb production.