Lodgepole pines, Pinus contorta var. latifolia Engelm., treated with the herbicide glyphosate applied by axe frill or drill hole into the sapwood around the root collar, were readily infested by mountain pine beetles, Dendroctonus ponderosae Hopk. On trees treated with 360 mg of glyphosate per centimetre of circumference, foraging woodpeckers, Picoides spp., debarked 15% of the bole surface within 10 weeks and > 30% after 1 year, compared with < 5% for controls. Foraging efficiency on mountain pine beetle at 4 m exceeded 90% after applications by axe frill of glyphosate at doses of 360, 36, and 3.6 mg per centimetre of circumference, compared with < 50% for controls. Glyphosate-treated trees rapidly became suitable for cavity excavation by woodpeckers.