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

Abstract Yellow toadflax is an invasive perennial broadleaf weed that negatively affects 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 because it may injure desirable vegetation. The effectiveness of wiper-applied glyphosate followed by (fb) applications of either chlorsulfuron or picloram was evaluated on yellow toadflax grown in a greenhouse. Glyphosate was applied with a wiper at 0% or 50% diluted concentrate. Chlorsulfuron (26 g ai ha −1 ) was applied alone or immediately after the wiper application of glyphosate. Picloram (560 g ae ha −1 ) was applied in a similar manner. At 3 mo after herbicide treatments, estimates of injury to yellow toadflax were greatest with glyphosate, glyphosate fb chlorsulfuron, and glyphosate fb picloram (77% to 86%) compared with chlorsulfuron or picloram applied alone (52% to 56%). The response of subsequently harvested biomass was not different after herbicide treatments. One month after treatment, flowering and regrowth of biomass and root biomass were quantified. Flowering, regrowth, and root biomass demonstrated the greatest (&gt;50%) recovery with wiper-applied glyphosate and wiper-applied glyphosate fb broadcast-applied chlorsulfuron or picloram compared with &lt;50% recovery with broadcast applications of chlorsulfuron or picloram. The results of the experiment suggest that wiper-applied glyphosate fb broadcast applications of chlorsulfuron or picloram can help manage yellow toadflax regrowth compared with single herbicide treatments.