Non-crop vegetation can compete with young conifers, potentially reducing conifer survival and growth rates. FRDA funded the establishment of several research trials designed to document the effect of herbicides (both registered and unregistered) and manual cutting on vegetation growth. This interm report summarizes the growth response of several vegetation species from one to five growing seasons after these treatments. Herbicides tested included glyphostate, hexazinone, triclopyr ester, sulfometuron methyl, and metsulfuron methyl. Manual cutting treatments were done throughout the growing season. A broad range of vegetation species were well controlled following application of glyphosate (1.8 kg a.i/ha). However Vaccunium spp., salal, red-osier dogwood, and hazelnut showed some tolerance. Glyphosate was generally most effective when applied later rather than earlier in the growing season. Hexazinone (4.0 kg a.i/ha) did not give effective control of vegetation species of concern in these coastal ecosystems. As a late-summer foliar treatment, triclopyr ester (2.9 kg a.e/ha) was less effective than glyphosate in controlling the non-crop species examined in these trials. Both thimbleberry and salmonberry showed a moderate degree of resistance. A wide range of vegetation species responses were displayed following application of sulfometuron methyl (0.60 kg a.i/ha) and metsulfuron methyl (0,12 kg a.i/ha). Conifers showed some intolerance to both chemicals. Since many prominent vegetation species in coastal forests resprouted vigorously following cutting of the above ground portions of the plant, manual cutting provided only short-term control of competing vegetation.
FRDA Research Report 135 (436 KB)
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Updated July 24, 2015