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1 November 2018 Efficacy of Halauxifen-Methyl on Glyphosate-Resistant Horseweed (Erigeron canadensis)
Cara L. McCauley, William G. Johnson, Bryan G. Young
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Halauxifen-methyl is a new synthetic auxin herbicide for control of broadleaf weeds, including preplant applications for corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. The objective of this study was to investigate the efficacy of halauxifen-methyl in comparison to the current auxin standards, 2,4-D and dicamba, on glyphosate-resistant (GR) horseweed (Erigeron canadensis L.) at different plant heights. In field experiments, a foliar application of halauxifen-methyl at the recommended use rate of 5 g ae ha-1 resulted in 81% control. Dicamba applied at 280 g ae ha-1 provided a comparable level of efficacy of 80%, while 2,4-D at 560 g ae ha-1 resulted in 49% control. The addition of glyphosate improved GR E. canadensis control with 2,4-D more than with halauxifen-methyl or dicamba, possibly due to the higher level of control observed with halauxifen-methyl or dicamba alone. Even though applied at 50 to 100 times lower application rates, the efficacy of halauxifen-methyl on E. canadensis was similar to dicamba and greater than 2,4-D. Thus, halauxifen-methyl should be an effective tool for management of GR E. canadensis before planting both conventional and herbicide-resistant soybean varieties, and it precludes the extended preplant application interval required for dicamba in some soybean management systems.

© Weed Science Society of America, 2018.
Cara L. McCauley, William G. Johnson, and Bryan G. Young "Efficacy of Halauxifen-Methyl on Glyphosate-Resistant Horseweed (Erigeron canadensis)," Weed Science 66(6), 758-763, (1 November 2018).
Received: 9 February 2018; Accepted: 14 June 2018; Published: 1 November 2018

2; 4-D
Arylpicolinate herbicide
Conyza Canadensis
Synthetic auxin herbicide
weed height
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