Submitted to: Pacific Northwest Vegetable Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/15/2009
Publication Date: 11/11/2009
Citation: Boydston, R.A. 2009. Weed and Onion Response to multiple Applications of Goal Tender beginning at the 1-Leaf Stage of Onion. Proc. Pacific Northwest Vegetable Assoc. Conference, Kennewick, WA. Available http://www.pnva.org/files/files/Onionoxyflourfen09-RickBo.pdf
Technical Abstract: Broadleaf weed control in onion is difficult in part due to a lack of postemergence herbicide options at an early growth stage of onions. Onion tolerance to sequential applications of oxyfluorfen (Goal-Tender) alone and with bromoxynil (Buctril) beginning at the 1-lf stage of onions was evaluated near Prosser, WA. Herbicide treatments were initiated when onions reached the 1 true leaf stage and sequential treatments were made at the 2-lf stage , 3-lf stage , and the 4-lf stage June 18, 2009. Oxyfluorfen and bromoxynil only slightly injured onions at all application dates tested. Onion injury mainly consisted of leaf tip burn, occasional necrotic spots on leaves, and curled leaves. In late June, treatments of Goal Tender inititated at he 1-lf stage and without any Buctril were injured the least .Buctril tank mixed with Goal Tender or Buctril alone tended to injure the onions slightly more than Goal Tender alone. Goal XL formulation also tended to injure onions greater than similar rates of Goal Tender. By 2 weeks after the last herbicide application, onion injury was less than 8% among all herbicide treatments . Common lambsquarters control in early June following the first herbicide applications at the 1-lf stage of onions, was greatest in plots treated with the highest rate of Goal Tender at 0.125 lb ai/a or with the 0.0625 lb ai/a rate of Goal Tender plus Buctril 0.03 lb ai/a, but was notcompletely controlled by any herbicide treatment . Lambsquarters that escaped initial treatments were never completely controlled by sequential herbicide treatments, but growth was greatly impeded and any new seedlings that emerged were controlled. All Goal Tender plus Buctril tank mixes the highest rate of Goal Tender alone, and Goal 2XL controlled common lambsquarters greater than 90% in late June. Hairy nightshade emerged later than common lambsquarters and all herbicide treatments controlled hairy nightshade 99 to 100%. Pigweed also emerged later than common lambsquarters and all herbicide treatments controlled pigweed well except Buctril alone. Common mallow emerged later than other broadleaf weeds and was completely controlled by all herbicide treatments.. Onion yield and size distrubution were not significantly different among herbicide treatments . Sequential applications of Goal Tender starting at the 1-lf stage of onion controlled all broadleaf weeds well without any increase in onion injury compared to Goal Tender applications starting at the 2-lf stage and could give growers an opportunity to treat weeds starting at a younger growth stage, thereby reducing the risk of weed control failure.