Injury to Peanut Cultivars from Postemergence Herbicide Tank-Mixtures with Paraquat.

The cancellation of dinoseb created a void in weed control programs for peanut (Arachis hypogaea L.) farmers. This led to the introduction of paraquat as a major herbicide for peanut in the Southeast. The objective was to establish a level of injury for and determine the effects on pod yield and grade from postemergence (POST) herbicide tank-mixtures including paraquat on runner-type peanut cultivars. Experiments were conducted under irrigation in 2016 & 2017 at Ty Ty, GA on a Tifton loamy sand and at Plains, GA on a Greenville sandy loam. Georgia-06G, Georgia-14N, TUFRunner™ ‘511’, and FloRun™ ‘157’ were the four cultivars evaluated. The herbicide tank-mixtures included 1. paraquat, 2. paraquat + acifluorfen + bentazon, 3. paraquat + acifluorfen + bentazon + S-metolachlor, and 4. paraquat + acifluorfen + bentazon + acetochlor. Injury (% leaf burn & % stunting) was rated at 4, 7, 11, and 14 days after treatment (DAT). Peanuts were dug at 150 days after planting. Yield (kg ha^-1) and grade (% Total Sound Mature Kernel [TSMK]) were evaluated after harvest. The value α = 0.10 was used for data analyzation. For both locations, herbicide treatment (p<0.0001) was significant for leaf burn and stunting injury. The paraquat treatment showed the greatest amount of injury at both locations (30-40%). For yield, there were no significant interactions between cultivar and herbicide treatment in Plains and Ty Ty (p=0.66 & p=0.95, respectively). TUFRunner™ '511' and Georgia-06G had the highest yield at both locations. In Plains, herbicide (p=0.09) and cultivar (p=0.07) were significant to grade. The acetochlor treatment may cause a grade reduction in heavier soil types (69 %TSMK). In Ty Ty, there were no significant effects or interaction effects on grade. While the greatest amount of injury occurs with the paraquat treatment, there is no supporting evidence that correlated this to lower yields when compared to the other treatments.