The Effect of Picloram Plus 2,4-Dichlorphenoxyacetic Acid on Peanut Growth and Yield

Picloram (4-amino-3,5,6-trichloropicolinic acid) injury, in the form of leaf roll, is often observed in peanut fields due to short crop rotations, contaminated irrigation water, treated hay, and contaminated livestock waste. Limited data on peanut response to picloram is available. Field trials were conducted near Tifton, GA from 2015-2017 to determine the effects of picloram plus 2,4-D (2,4-dichlorophenoxyacetic acid) on peanut growth and yield. Picloram plus 2,4-D was applied to ‘GA-06G' peanut at four different timings: preemergence (PRE), 30 d after planting (DAP), 60 DAP, and 90 DAP. At each timing, three rates of picloram plus 2,4-D were applied including the following: 1/10thX (0.18 + 0.67 kg ai/ha); 1/100thX (0.018 + 0.067 kg ai/ha); and 1/300thX (0.006 + 0.023 kg ai/ha). A non-treated control (NTC) or 0 rate was included for comparison. Peanut plant density was not influenced by any rate or timing of picloram plus 2,4-D. For peanut injury (leaf roll), a significant rate x timing interaction was observed (P=0.047). At 120 DAP, leaf roll was significant for the 1/10thX rate applied at 30, 60, and 90 DAP, the 1/100thX rate applied at 60 and 90 DAP, and for the 1/300thX rate applied at 90 DAP. When averaged over timing, peanut height at 120 DAP was significantly reduced by the 1/10thX and 1/100thX rates. When averaged over rate, peanut height reductions were greatest when picloram plus 2,4-D was applied at 60 DAP. When averaged over timing, only the 1/10thX rate caused significant yield reductions (11%). When averaged over rate, timing had no effect on yield (P=0.5403). Peanut fields unintentionally exposed to picloram plus 2,4-D rates ≤ 1/100thX can exhibit typical injury symptoms but most likely will not experience yield losses.