Managing individual juniper and pinyon infestations with pelleted tebuthiuron or picloram

Abstract

Junipers (Juniperus spp.) and pinyons (pinus edulis Engelm.) are reinfesting areas from which they have been removed and are encroaching into other areas. Controlling these trees while they are small would help maintain forage production and protect the soils. Individual trees can be controlled by applications of pelleted picloram (4amino-3,5,6-trichloro-2-pyridinecarboxylic acid) and tebuthiuron [N-[5-(1,l-dimethylethyl)-l,3,4thiadiazol-2-yl]N-N-dimethylurea), but little is known of the comparative effectiveness of these herbicides on junipers and pinyon. We compared pelleted picioram and tebuthiuron on individuai alligator juniper (J. deppeana Steud.), one-seed juniper [J. monosperma (Engelm.) Sarg.], Utah juniper [J. osteosperma (Torr.) Little], and pinyon. Pellets were applied at 0.7 and 1.4 g picloram acid equivalent (a.e.) or tehuthiuron active ingredient (a.i.)/m of tree height at 3 Arizona and 3 New Mexico locations. Utah juniper and pinyon trees up to 2 m tall were killed with 0.7 g picloram a.e. or tebuthiuron a.i./m of height. One-seed junipers up to 2-m tall were killed by 0.7 g tebuthiuron a.i./m of height, but were not by picloram. Neither herbicide killed alligator juniper consistently. Some understory grasses were damaged more by tebuthiuron than by picloram.