Karbutilate for Weed Control on Sagebrush Rangelands

Abstract

Procedures were developed for simultaneous control of big sagebrush(Artemisia tridentataNutt.), green rabbitbrush [Chrysothamnus viscidiflorusVar.Viscidiflorus(Hook.) Nutt.] and downy brome(Bromus tectorumL.) with the herbicide karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1, 1-dimethylurea]. After a season of fallow, the herbicide-treated areas were seeded with perennial grasses. During the 4 yr of testing at several locations, karbutilate at 1.1 kg/ha controlled the shrubs and downy brome. A herbaceous fallow was maintained with 0.6 kg/ha of the herbicide, but 1.1 kg/ha was necessary for green rabbitbrush control. Perennial grass seedling establishment was highly variable among sites and years of testing. If germination of the seeded species occurred in the fall, stands were poor. When germination was delayed by the onset of cold weather until spring, excellent stands were obtained on plots treated 1 yr previous to seeding with 1.1 kg/ha of karbutilate. Residual herbicide activity was harmful at the time of fall seeding but herbicide residues declined by spring as shown by bioassay of soils.