Sesame (Sesamum indicum L.) Response to Combinations of Ethalfluralin Plus S-metolachlor Applied Prior to Planting

Aims: Determine sesame response to ethalfluralin at 0.63, 0.84, or 1.05 kg ha-1 in combination with S-metolachlor at 1.07 or 1.42 kg ha-1 applied and incorporated prior to planting.

Study Design: Randomized complete-block with 3 replications.

Place and Duration of Study: Studies conducted during the 2019 growing season in the Southern High Plains region of Texas near New Deal (33.5818o N, -101.7794o W) and in south Texas near Yoakum (29.2756o N, -97.1226o W).

Methodology: At New Deal, two passes (in opposite directions) using a rolling cultivator with mixing wheels was used to incorporate herbicides within one hour of application. Mixing wheels consists of four to six spider gangs approximately 10 to 13 cm long mounted on a gang tube and set to incorporate the herbicide no greater than 2.0 cm. At the Yoakum locations, listed bed tops were cut so that they were no greater than 7 cm tall. At Yoakum 1, after beds were knocked down, herbicides were applied and incorporated approximately 2.0 cm deep with a similar piece of equipment as used at New Deal. At Yoakum 2, only the mixing action of the Monosem® precision planter was used to incorporate herbicides.

Results: At Yoakum, Urochloa texana (Buckl.) control with all ethalfluralin plus S-metolachlor treatments when evaluated 31 to 39 DAP was inconsistent and varied from 62 to 95% while Amaranthus palmeri S. Wats control was 98 to 100% and Trianthema portulacastrum L. control was 81 to 99%. At New Deal, only ethalfluralin at 0.84 kg ha-1 + S-metolachlor at 1.42 kg ha-1 did not reduce stand. All treatments caused sesame injury when evaluated 16 and 72 days after planting; only ethalfluralin at 1.05 kg ha-1 + S-metolachlor at 1.42 kg ha-1 reduced yield. At Yoakum, all herbicide treatments reduced yield regardless of incorporation method (mixing wheel vs planter action).