NONTARGET EFFECT OF HERBICIDES .2. THE INFLUENCE OF GLYPHOSATE ON ECTOMYCORRHIZAL SYMBIOSIS OF RED PINE (PINUS-RESINOSA) UNDER GREENHOUSE AND FIELD CONDITIONS

The effects of the herbicide glyphosate [N‐(phosphonomethyl)glycine]on seedling growth of Pinus resinosa and on the ectomycorrhizal development of the symbiotic fungus Paxillus involutus were investigated under greenhouse and field conditions. Glyphosate at 0–54 and 3–23 kg ha−1 did not reduce seedling growth or ectomycorrhizal development under greenhouse conditions. There was no seedling mortality due to glyphosate treatment at either rate. Under field conditions, seedling growth of P. resinosa and ectomycorrhizal development of P. involutus were not affected by the above rates. Seedlings (46–48%) failed to survive in non‐glyphosate‐treated plots, presumably because of weed competition, whereas all survived in glyphosate‐treated plots. All the non‐mycorrhizal seedlings were colonized bv indigenous mvcorrhizal fungi within 2 months after planting in both control and glyphosate‐treated plots. The injection rates varied from 74–86 %. Copyright © 1990 Wiley Periodicals, Inc., A Wiley Company