Effect of wiper-applied glyphosate followed by chlorsulfuron or picloram on yellow toadflax ( Linaria vulgaris )

Yellow toadflax is an invasive perennial broadleaf weed that negatively impacts forage production and wildlife habitat. Few herbicides effectively manage this weed. Glyphosate is a nonselective herbicide that can help manage yellow toadflax but is rarely used in pasture/rangeland due to injury to desirable vegetation. The effectiveness of wiper-applied glyphosate followed by (fb) either chlorsulfuron or picloram was evaluated on yellow toadflax grown in the greenhouse. Glyphosate was applied with a wiper at 0 or 50% diluted concentrate. Chlorsulfuron at 26 g ai ha -1 was applied alone or immediately after the wiper application of glyphosate. Picloram at 560 g ae ha -1 was applied in a similar manner. Injury estimates on yellow toadflax were greatest with glyphosate, glyphosate fb chlorsulfuron, and glyphosate fb picloram (77 to 86%) compared with chlorsulfuron and picloram alone (52 to 56%) three months after treatment. The response of subsequently harvested biomass was not different for herbicide treatments. One month after treatment, flowering, regrowth of biomass, and root biomass were quantified. Wiper-applied glyphosate and wiper-applied glyphosate fb broadcast chlorsulfuron or picloram reduced >50% flowering, regrowth, and root biomass the greatest compared with broadcast applications of chlorsulfuron or picloram <50%. The results of the experiment suggest that wiper-applied glyphosate fb broadcast applications of chlorsulfuron or picloram help manage yellow toadflax regrowth compared with single herbicide treatments.