Evaluating herbicide programs for peanut response and weed control

Field research evaluated peanut (Arachis hypogaea L.) tolerance and weed control with preemergence (PRE) followed by early postemergence (EPOST) herbicide programs: PRE pyroxasulfone, S-metolachlor, flumioxazin, pendimethalin, ethalfluralin, diclosulam, or dimethenamid-P, followed by EPOST application of paraquat + acetochlor + bentazon at 4 wk after PRE (WA-PRE). The herbicides resulted in no differences in peanut injury at 2 WA-PRE in 2019 but flumioxazin resulted in approximately two-fold greater injury (>22%) than other treatments in 2020 because of heavy rainfall at peanut cracking. Palmer amaranth (Amaranthus palmeri S.Watson) control with diclosulam was lower than with other herbicides. Carpetweed (Mollugo verticillata L.) control with S-metolachlor and dimethenamid-P was at least 10% lower than with pendimethalin, flumioxazin, or pyroxasulfone at 4 WA-PRE. Palmer amaranth control 2 wk after the EPOST (WA-EPOST) application was >94% for all treatments except diclosulam. Peanut injury at 2 WA-EPOST was <= 28% but was minimal by 8 WA-EPOST. Overall, yield with herbicide treatments was similar to the weedfree control. A greenhouse experiment evaluated postemergence herbicide combinations for Palmer amaranth control, including 2,4-DB, acifluorfen, imazapic, bentazon + acifluorfen, pyroxasulfone + carfentrazone, and various combinations of each. Palmer amaranth control (>= 99%) was greater and biomass (<= 0.3 g plant(-1)) was lower with acifluorfen treatments than with other treatments. The 2,4-DB + pyroxasulfone + carfentrazone treatment provided similar control to acifluorfen treatments. The EPOST paraquat + acetochlor + bentazon combinations following an effective PRE program will effectively control Palmer amaranth in peanut. Additionally, greenhouse experiments supported the use of acifluorfen for postemergence Palmer amaranth control.