Growers and landscapers are often faced with weed problems in ornamentals that cannot be controlled with selective herbicides. In landscape situations, glyphosate is mainly used as a nonselective herbicide. However, researchers have reported that many plants have significant tolerance to over-the-top applications of glyphosate when applied at rates between 0.1 and 2.0 lb/acre (Ahrens, 1974; Altland et al., 2002; Bing, 1974; Butler and Burnside, 1983; Derting et al., 1973; Olinger, 1982; Perry and Knowles, 1979; Putnum, 1976; Self, 1978). Also, Neal and Skroch (1985) determined that damage from glyphosate applications could be influenced by the time of year and growth stage of the treated plant. Moreover, Neal and Skroch also indicated that shore juniper absorbed carbon-14-labeled glyphosate during shoot elongation, but no significant absorption of glyphosate occurred when applications were made to shore juniper that were cold acclimated, winter dormant, at budbreak, or at termination of first flush of growth. Although risk is of plant damage is a concern, growers and landscapers have considerable interest in determining if glyphosate applications can be used on select plant material to remove problem weeds. The objective of this research was to determine the highest rate of glyphosate that three different species of juniper could tolerate when glyphosate treatments were applied after the termination and maturity of the first flush of growth.
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