Selective Application of Glyphosate for Control of Larkspurs (Delphiniumspp.)

Abstract

Glyphosate effectively kills duncecap and tall larkspur on mountain rangelands but it is nonselective and kills all other vegetation it contacts. Two selective application methods to treat individual plants were compared to demonstrate their efficacy in controlling larkspur and their effect on associated plant species: (1) spot spray with glyphosate concentration at 2% product solution (0.8% ai); (2) hand held wiper applicator with glyphosate concentration at 33% production solution (13.5% ai). The two methods were equally effective in killing most of the larkspur plants, but the sprayer applicator was more rapid and easier to apply. Neither method adversely affected foliar cover of associated perennial species. Glyphosate must be applied to the entire plant to ensure its mortality.