Control of Rocky Mountain Iris and Vegetation Response on Mountain Meadows

Abstract

Application of 2, 3, or 4 lb/acre of 2,4-D in mid-June or 3 or 4 lb/acre in early July gave 91 to 100% control of iris. Iris phenology at treatment ranged from late vegetative to late bloom. The 2 lb/acre rate applied when seed capsules were forming controlled 73 to 85% and control was not uniform. Reduction in iris yield ranged from 398 to 1568 lb/acre and averaged 925 lb/acre. Iris control gave a significant increase in production of grass and grasslike species of from 274 lb/acre (58%) to 2364 lb/acre (360%) with an average of 1173 lb/acre (180%). Slender wheatgrass and Nevada bluegrass were the most responsive species. Yield of sage grouse food plants, dandelion and yarrow, was severely reduced the first year after all treatments. Total forb production was deficient or minimal for sage grouse, and dandelion was deficient. Total forb production and dandelion component appeared adequate for existing sage grouse populations in the second and subsequent years after treatment.