Difficulty in Controlling Duncecap Larkspur (Delphinium occidentale)

Abstract

Duncecap larkspur was not killed by triclopyr, picloram, or clopyralid applied once at recommended rates. Triclopyr at 1.1, 1.7, 2.2, and 4.6 kg ae/ha applied twice to the same plots in two consecutive years reduced duncecap larkspur density from 29 to 64%. However, the higher rates of triclopyr left 2 plants/m2, an unacceptable level for preventing cattle poisoning.