Interactions of pinyon and juniper trees with tebuthiuron applications at 2 matched reinvaded sites in Utah

Abstract

Four rates (0.12, 0.25, 0.50, and 0.75 gm a.i. per 130 dm3 crown volume) of tebuthiuron boluses were applied to tree stembase, mid-crown, or dripline placements. Four size classes of Utah juniper Juniperus osteosperma, and single needle Pinus monophylla and Rocky Mountain P. edulis pinyon trees were treated in September 1985. Defoliation and mortality levels were estimated 24 and 36 months following treatments. The presence and strength of main effects and first order interactions was largely site-specific. Pinyon was more susceptible than juniper at either site. Medium-sized and large saplings were more readily defoliated than seedlings and small saplings. The highest, most rapid and most uniform defoliation and mortality of trees resulted from application of tebuthiuron at the stem bases. This placement option has strong operational advantages and minimizes damage to forage plants beneath trees. -from Authors