Canadian Forest Service Publications
Growth response of conifers following control of Kalmia angustifolia L. 1997. Titus, B.D.; English, B Pages 141-147 in P.G. Comeau and G.J. Harper, compilers. Expert Committee on Weeds, Proceedings: of the 1996 National Meeting. December 9-12, 1996, Victoria, BC. BC Ministry of Forests, Victoria, BC.
Issued by: Pacific Forestry Centre
Catalog ID: 18838
Scarifiction (disc trenching) more than doubled third-year leader growth of black spruce, jack pine and eastern larch seedlings planted on a site invaded by Kalmia angustifolia near Botwood, central Newfoundland. Treating Kalmia with a combination of herbicides further enhanced conifer growth, but not as much as use of NPK fertilizer at planting. The best growth was obtained when scarification, herbicide application and fertilization were combined. The beneficial results of applying herbicides were obtained even though Kalmia stocking was only reduced from 89% to 72%. Three-year top height of larch was greater than pine, which was greater than spruce. However, third-year leader growth was greater for pine than for larch. There was no difference in conifer survival between scarified sites that were treated with herbicides (91-97%) and those that were not (88-98%), suggesting that Kalmia does not reduce survival of planted conifers. Survival was > 90% even on untreated control plots.
A second set of trials demonstrated that early July applications of glyphosate or triclopyr at 6 L ha -1 with or without a surfactant (Sylgard®) were not as successful in controlling Kalmia as late August applications. Glyphosate controlled sprouting from dead Kalmia stems and regeneration from rhizomes more effectively than triclopyr. Sylgard® generally increased the efficacy of glyphosate and triclopyr, and improved the “rain fast-ness” of glyphosate. However, use of Sylgard® increased damage to conifers. Glyphosate + Sylgard® in late August was best for control of Kalmia, but glyphosate or triclopyr alone caused less damage to spruce seedlings.