Peanut tolerance to soil and foliar applications of Triclopyr

The abundance and close proximity of pine trees (Pinus spp.) and peanut (Arachis hypogaea L.) in Georgia have resulted in off-target movement of forestry herbicides, including triclopyr, into peanut fields. Currently, no information is available evaluating peanut response to triclopyr. Research was conducted from 2020-2022 near Ty Ty, Georgia to determine peanut response to triclopyr applied preemergence (PRE), 1 day after planting (DAP), or postemergence [(POST) 30 DAP or 60 DAP] at five rates including 0, 8.4 (1/100X), 84 (1/10X), 168 (1/5X), and 840 g ae/ha (1X, manufacturers suggested use rate). Peanut density (stand), growth, and yield were not reduced when triclopyr was applied PRE at rates ≤ 168 g ae/ha. Triclopyr at 840 g ae/ha applied PRE reduced peanut density by 52%, visual plant growth by 32%, and yield by 22%. Significant reductions in plant growth were also observed with POST applications of triclopyr ≥ 168 g ae/ha applied 30 DAP. However, only the 840 g ae/ha rate resulted in plant height reductions (29%) and yield losses (42%) when applied at this time. When applied 60 DAP, triclopyr at 168 and 840 g ae/ha caused height reductions (17% to 46%) and yield reductions (24% to 62%). These results suggest that peanut should not be planted in fields exposed to full rates of triclopyr until rates decline to ≤ 168 g ae/ha (~three half-lives or 138 d). Peanut exposed to POST applied triclopyr at rates ≤ 84 g ae/ha (1/10X) during the growing season should not experience significant growth inhibition or yield loss.