Abstract
Metamitron, a Group 5 herbicide, was granted an emergency use label for 2024 in 10 and 14 counties in Colorado and Nebraska, respectively, for control of herbicide-resistant (HR) Palmer amaranth (Amaranthus palmeri) in sugar beet. The 2024 emergency use label, however, was restrictive, allowing sugar beet growers to only apply 3.27 kg ai ha-1 before sugar beet emergence. In situations where sugar beet growers miss a PRE application before HR-Palmer amaranth emergence, there is no option for HR-Palmer amaranth control before the 2TL stage. In 2024, studies were conducted in Scottsbluff, NE, to evaluate weed control efficacy under the terms of the 2024 label. Common lambsquarters (Chenopodium album) control was excellent with the use of metamitron compared with the non-treated check and ethofumesate. HR-Palmer amaranth was controlled with metamitron compared with the non-treated check. In a later study, sugar beet safety was assessed when herbicide is applied off-label. Weed control did not improve when metamitron was applied at the cotyledon stage; however, control was excellent when followed up with metamitron + ethofumesate + s-metolachlor at the 2 TL. Crop safety was excellent with no noticeable injury and decrease in crop stand. Metamitron can effectively manage HR-weeds in sugar beets but should be followed up with Group 15 herbicide to maximize efficacy.
