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

Abstract

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.