Performance of Pyroxasulfone to Control Amaranthus palmeri and Salsola kali in Peanut

Aims: Determine weed efficacy and peanut tolerance to pyroxasulfone in the Texas High Plains peanut growing area.

Study Design: Randomized complete block design with 3 replications.

Place and Duration of Study: Weed efficacy studies were conducted during 2013 and 2014 at the Texas A&M AgriLife Research and Extension Center near Halfway (34.188o N, 101.952o W) and near Seagraves (32.9369o N, 102.5409o W). Peanut tolerance studies were conducted during 2014 and 2015 near Brownfield (33.1042o N, 102.1615o W).

Methodology: Plots were four rows wide spaced 102 cm apart and 9.5 m long. Herbicides were applied with a CO2 compressed-air backpack sprayer using Teejet Turbo Tee 11002 flat fan nozzles which delivered 140 L ha-1 at 207 kPa. In the weed efficacy studies, field plots were naturally infested with moderate Palmer amaranth (Amaranthus palmeri S. Wats.) populations while Russian thistle (Salsola kali L.) populations were low to moderate. Weed control and peanut injury was visually estimated on a scale of 0 indicating no control and 100 indicating complete control or plant death, relative to the untreated control. In the variety tolerance study, pyroxasulfone alone at 0.09 and 0.18 kg ha-1 was compared with flumioxazin + pyroxasulfone at 0.07 + 0.09 and 0.14 + 0.18 kg ha-1, respectively applied PRE. This area was kept weed-free.

Results: Pyroxasulfone, applied either PRE or EPOST, provided at least 95% A. palmeri control while pyroxasulfone applied PRE followed by paraquat applied EPOST controlled Salsola kali 97%. This was as good as all other herbicide treatments with the exception of either pyroxasulfone or dimethenamid-P plus paraquat applied EPOST and followed by imazethapyr applied LPOST, which provided only 58% control.

Conclusion: These results indicate that pyroxasulfone can be an effective herbicide for control of Amaranthus palmeri and Salsola kali in peanut. All peanut varieties evaluated showed excellent tolerance to pyroxasulfone.