Weed Control and Peanut Tolerance Using Pyroxasulfone in Oklahoma

Aims: To determine the spectrum of weed control and peanut tolerance with pyroxasulfone in Oklahoma.

Study Design: Randomized complete block design with four replications.

Place and Duration of Study: Oklahoma State University Caddo Research Station near Ft. Cobb (35.091º N, 98.275º W) in southwestern Oklahoma during the 2013-2014 growing seasons.

Methodology: Herbicides were applied with a CO2 compressed air backpack sprayer using Teejet 110015XR nozzles that delivered 93 L ha-1 at 180kPa. Weed control and peanut injury were visually estimated on a scale of 0 indicating no control or plant death to 100 indicating complete control or plant death, relative to the untreated control. Peanut yields were obtained by digging each plot separately, air-drying in the field for 4 to 7 d, and harvesting peanut pods from each plot with a combine. Visual estimates of weed control and peanut yield were subjected to analysis of variance to test effects of postemergence (POST) herbicide and application timing and means were compared with Fisher’s Protected LSD test (0.05).

Results: In 2013, only treatments that controlled Urochloa texana > 85% were those that included pendimethalin plus pyroxasulfone applied preemergence (PRE) and imazapic applied late postemergence (LPOST). Ipomoea hederacea control using either pendimethalin applied preplant incorporated (PPI) or flumioxazin applied PRE and imazethapyr applied POST was ≥ 75%. In 2014, herbicide systems that included imazapic applied POST controlled I. hederacea at least 98% while no other herbicide systems provided better than 78% control. Peanut stunting (4 to 13%) was observed in 2013 with all PPI and PRE treatments. In 2013 and 2014, pyroxasulfone plus pendimethalin systems applied PRE followed by imazapic applied LPOST produced the greatest peanut stunting.

Conclusion: These results indicate that pyroxasulfone is an effective herbicide for weed control in Oklahoma peanut production. Although no peanut yield reductions were observed, the early season stunting in isolated instances should be noted.