Evaluating Herbicide Programs for Effective Weed Control in South Texas Peanut (Arachis hypogaea L.) Production

Aims: To evaluate peanut tolerance and weed efficacy with various peanut herbicide programs.

Study Design: Randomized complete block.

Place and Duration of Study: Field studies were conducted during the 2018, 2021, and 2022 growing seasons in the south Texas peanut growing region.

Methodology: A weed-free study was conducted in 2018 to evaluate crop safety while in 2021 and 2022 weed efficacy trials were conducted. The weed-free study was taken to yield; however, the weed efficacy studies were not.

Results: No noticeable peanut injury with any herbicide program was noted in 2018; however, paraquat + imazethapyr applied at cracking produced the lowest yield. In the 2021 and 2022 studies, peanut stunting was noted with all herbicide systems which included paraquat. Amaranthus palmeri control was > 95% with pendimethalin + flumioxazin + S-metolachlor applied preemergence or any herbicide systems that included S-metolachlor + 2,4-DB applied postemergence. Pendimethalin alone provided 83% control of Urochloa texana while herbicide systems that contained multiple herbicides provided > 90% control. Similar results were seen with Cucumis melo. Ipomoea hederacea L. required the use of multiple herbicides to provide effective control. Pendimethalin alone or paraquat + pyroxasulfone provided <70% control while systems which included pendimetahlin + either S metolachlor, the premix of carfentrazone + pyroxasulfone, or imazapic provided 100% control.

Conclusion: These studies indicate that grower concerns about peanut injury are largely unfounded as only paraquat-containing herbicide systems consistently resulted in any stunting. The premix of carfentrazone + pyroxasulfone caused leaf burn; however, peanuts recover quickly with no yield reduction. Although the premix of carfentrazone + pyroxasulfone systems provided excellent control of U. texana, typically this combination does not effectively control large-seeded annual grasses. Other herbicide systems which included pendimethalin plus either S-metolachlor, flumioxazin + S-metolachlor, dimethenamid, or imazapic provided excellent weed control. These herbicide systems offer growers another option to help provide season-long weed control in the southwestern US peanut production areas.