Journal of Experimental Agriculture International

Background: Since peanut fields are often treated with fungicides during the growing season to control stem rot disease (caused by Sclerotium rolfsii Sacc.) and early and late leaf spot disease [caused by Cercospora arachidicola Hori) and Cercosporidium personatum (Berk. & M.A. Curtis) Deighton, respectively], weeds can also interfere with the uniform deposition of fungicides and therefore reduce disease control.

Aims: The present study evaluates weed control and peanut response with the premix of carfentrazone plus pyroxasulfone (C + P).

Study Design: Randomized complete block design with 3 to 4 reps depending on location.

Place and Duration of Study: During the 2022 through 2024 growing seasons in the Texas Rolling Plains near Vernon and in south Texas near Yoakum.

Methodology: Plots at Yoakum consisted of two rows spaced 97 cm apart and 7.6 m long while at Vernon plots were 2 rows spaced 102 cm apart by 7.6 m long in 2022 and 2024 and 4 rows spaced 102 cm apart by 18.2 m long in 2023. Preemergence (PRE) treatments were applied 2 to 10 days after planting (DAP). Peanut cracking (CRACK) treatments were applied 4 to 10 DAP. Postemergence (POST) treatments were applied 30 to 40 DAP. Weed control and peanut injury data were arcsine transformed prior to analysis of variance. Means were compared with Fisher’s Protected LSD test at the 5% probability level.  The untreated control was not included in the weed control analysis but was included in the yield analysis. 

Results: In south Texas, Palmer amaranth (Amaranthus palmeri S. Wats.) control was > 90% with either pendimethalin applied PRE followed by (fb) S-metolachlor applied at CRACK fb C + P plus clethodim applied POST or S-metolachlor plus paraquat applied at CRACK fb S-metolachlor plus clethodim applied POST.  All herbicide systems which contained C + P controlled Texas millet [Urochloa texana (Buckl.)] 87 to 98% while Smellmelon (Cucumis melo L. var. Dudaim Naud.) control with C + P systems ranged from 58 to 100%. In the Rolling Plains, A. palmeri and U. texana control was most consistent (76 to 91%) with C + P applied both at CRACK and POST.  Under moderate A. palmeri pressure (4 to 5 plants/m²), all herbicide systems increased peanut yield over the untreated check (65%), while with no weed pressure, no differences in yield were noted with any herbicide treatment from the untreated check.

Conclusion: The premix of C + P can help peanut producers manage their annual broadleaf weed problems. Broadleaf weeds cause Texas peanut growers considerable problems and can be hard-to-control with many of the presently used herbicides.  Oftentimes, the premix of C + P does not effectively control large-seeded annual grasses such as Texas millet and requires the use of a graminicide such as fluazifop-P-butyl, clethodim, or sethoxydim (WSSA Group 1 herbicides) to improve season-long control.