Abstract
Aims: Determine the influence of sequential spray order and role of glufosinate when used in a system with dicamba to control Palmer amaranth at three different growth stages. Study design: Randomized complete block design with four replications Place and duration of Study: A fallow, non-crop field at the Texas A&M AgriLife Research and Extension Center, Lubbock, Texas, during the 2018-2019 growing seasons Methodology: Herbicides were applied to < 10 cm, 10 to 20 cm, and > 30 cm Palmer amaranth with a handheld 1.93m CO2-pressurized backpack calibrated to deliver 140 L ha-1 at 207 kPa. Palmer amaranth control was visually estimated on a scale of 0 (no control) to 100% (complete plant death) relative to the nontreated control. Palmer amaranth biomass and density were taken when all plots reached 50% or less control in 2019. Palmer amaranth control, biomass, and density were subjected to analysis of variance and means were separated using Fisher’s Protected LSD at an alpha of 0.05. Results: Palmer amaranth control decreased as Palmer amaranth size at initial application increased. A difference in efficacy based on herbicide order was observed for < 10 cm Palmer amaranth. Glufosinate followed by dicamba was less effective (76-83%) than dicamba followed by glufosinate (93-96%) at 2 of 4 rating dates following sequential applications in both years. Dicamba + acetochlor followed by glufosinate provided greater Palmer amaranth control than dicamba followed by dicamba at one or more rating dates across all weed sizes. Conclusion: Glufosinate served as a complimentary partner in the dicamba-based system, and additional modes of action will be more effective to slow the development of resistance to group 4 herbicides when compared to repeated use of a group 4 herbicide used alone.
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Claims 5
Claim · model-written summary
Palmer amaranth control decreased as the weed was larger at the initial application.
Verbatim
e0“Palmer amaranth control decreased as Palmer amaranth size at initial application increased”
Claim · model-written summary
Efficacy of glufosinate and dicamba sequences on Palmer amaranth under 10 cm depended on herbicide order.
Verbatim
e1“A difference in efficacy based on herbicide order was observed for < 10 cm Palmer amaranth”
Claim · model-written summary
Glufosinate followed by dicamba was less effective on Palmer amaranth than dicamba followed by glufosinate at 2 of 4 rating dates.
Verbatim
e0“Palmer amaranth control decreased as Palmer amaranth size at initial application increased”
e2“Glufosinate followed by dicamba was less effective (76-83%) than dicamba followed by glufosinate (93-96%) at 2 of 4 rating dates following sequential applications in both years”
Claim · model-written summary
Dicamba plus acetochlor followed by glufosinate gave greater Palmer amaranth control than dicamba followed by dicamba at one or more rating dates.
Verbatim
e3“Dicamba + acetochlor followed by glufosinate provided greater Palmer amaranth control than dicamba followed by dicamba at one or more rating dates across all weed sizes”
Claim · model-written summary
Additional herbicide modes of action are suggested to slow resistance to group 4 herbicides in Palmer amaranth.
Verbatim
e3“Dicamba + acetochlor followed by glufosinate provided greater Palmer amaranth control than dicamba followed by dicamba at one or more rating dates across all weed sizes”
e4“additional modes of action will be more effective to slow the development of resistance to group 4 herbicides when compared to repeated use of a group 4 herbicide used alone”