Effects of manual application method on application time, thoroughness, and tebuthiuron outlays

Abstract

Small-plot trials of effective herbicides for manual woody-weed treatments should be validated on large tracts where rapidity, thoroughness, and efficiency of application are integral to operational-scale recommendations. A 7.9 hectare woodland chaining in Utah, with 248 Juniperus osteosperma Torr. (Little) and Pinus monophylla Torr. & Frem. saplings per ha, was divided into nine 25-m by 350-m strips for timed tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea) manual application trials in fall 1986 and summer 1987. About 1 ha was treated per hour, and 6 to 15% of the trees were missed. Three application methods differed in total and aggregate time outlays, accuracy, and tediousness, but were highly similar in formulated tebuthiuron expenditures of 1.5 to 2.0 kg/ha (0.21 to 0.28 kg/ha tebuthiuron a.i.). Time expenditures were moderately predictable (r2=0.62) from treated tree density and mean tree height, whereas percent trees missed was unrelated to density or method. Placing herbicide particles at the stem base and basing dosages on stem height are preferable to dripline applications and crown-volume based dosage estimations.