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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #307149
Title: Broadleaf weed control in irrigated pastures containing Trifolium repens

Author
item DAVY, JOSH - University Of California - Cooperative Extension Service
item KARLE, BETSY - University Of California - Cooperative Extension Service
item KYSER, GUY - University Of California
item DITOMASO, JOSEPH - University Of California - Cooperative Extension Service
item Rinella, Matthew - Matt

Submitted to: California Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2015
Publication Date: 9/5/2015
Citation: Davy, J.S., Karle, B.M., Kyser, G.B., Ditomaso, J.M., Rinella, M.J. 2015. Broadleaf weed control in irrigated pastures containing Trifolium repens. California Agriculture. 66:985-991.

Interpretive Summary: Increasing irrigated pasture lease and purchase costs are encouraging producers to use herbicides to control broadleaf weeds and maximize forage production on their current land base as opposed to seeking out additional pastureland. There are two challenges to using herbicides to control broadleaf weeds in irrigated pasture. One challenge is that producers often encounter weed species for which herbicide information is limited or nonexistent. Another challenge is that the broadleaf herbicides tend to damage desirable legumes. We evaluated efficacy of several broadleafherbicide options for slender aster, a species previously subjected to little or no herbicide research We also monitored herbicide impacts on desirable legumes, principally white clover. We also evaluated control of field bindweed and buckhorn plantain, subjects of considerable past herbicide research. Our goal was to identify herbicide options that controlled all three weeds while causing the least damage to legumes.Several rates and combinations of dicamba, diflufenzopyr, triclopyr, MCPA, and 2,4-D provided similar control of field bindweed and buckhorn plantain, with estimates suggesting 66-88% control in 2011 and 43-86% control in 2012. 2,4-D+triclopyr provided the best control of buckhorn plantain and field bindweed. This combination also provided the best control of slender aster, with estimates for high rates indicating nearly 100% control both years. However, 2,4-D+triclopyr appeared particularly damaging to legumes. Based on these findings, we recommend 2,4-D+triclopyr where desirable legumes are absent. Where desirable legumes are present, we recommend 2,4-D alone. Whereas 2,4-D alone appeared to underperform 2,4-D+triclopyr at controlling slender aster in 2012, 2,4-D alone appeared relatively less damaging to desirable legumes.

Technical Abstract: Increasing irrigated pasture lease and purchase costs are encouraging producers to use herbicides to control broadleaf weeds and maximize forage production on their current land base as opposed to seeking out additional pastureland. There are two challenges to using herbicides to control broadleaf weeds in irrigated pasture. One challenge is that producers often encounter weed species for which herbicide information is limited or nonexistent. Another challenge is that broadleaf herbicides tend to damage desirable legumes. We evaluated efficacy of several broadleaf herbicide options for slender aster, a species previously subjected to little or no herbicide research. We also monitored herbicide impacts on desirable legumes, principally white clover. We also evaluated control of field bindweed and buckhorn plantain, subjects of considerable past herbicide research. Our goal was to identify herbicide options that controlled all three weeds while causing the least damage to legumes. Several rates and combinations of dicamba, diflufenzopyr, triclopyr, MCPA, and 2,4-D provided statistically indistinguishable control of field bindweed and buckhorn plantain, with point estimates suggesting 66-88% control in 2011 and 43-86% control in 2012. According to point estimates, 2,4- D+triclopyr provided the best control of buckhorn plantain and field bindweed. This combination also provided the best control of slender aster, with point estimates for high rates indicating nearly 100% control both years. However, 2,4-D+triclopyr appeared particularly damaging to legumes. Based on these findings, we recommend 2,4-D+triclopyr where desirable legumes are absent. Where desirable legumes are present, we recommend 2,4-D alone. Whereas 2,4-D alone appeared to underperform 2,4-D+triclopyr at controlling slender aster in 2012, 2,4-D alone appeared relatively less damaging to desirable legumes.