Biologically effective dose of pyraflufen-ethyl/2,4-D, applied preplant alone or mixed with metribuzin on glyphosate-resistant horseweed in soybean

Abstract

Glyphosate resistance in weed species has presented immense challenges for farmers in Ontario. The co-application of burndown plus residual herbicides provides control of glyphosate-resistant (GR) horseweed control in soybean. Pyraflufen-ethyl/2,4-D is a premixed herbicide formulation sold under the tradename Blackhawk®. Five field experiments were conducted over a two-year period (2019, 2020) in fields in southwestern Ontario to ascertain the biologically-effective-dose of pyraflufen-ethyl/2,4-D, applied alone, or mixed with metribuzin, for GR horseweed control when applied pre-plant to soybean. Soybean visible injury for all treatments was <15%. At 8 wk after application (WAA), the calculated doses of pyraflufen-ethyl/2,4-D for 50, 80, and 95% GR horseweed control were 390, 1148, and >2108 g ha−1, respectively. The addition of metribuzin to pyraflufen-ethyl/2,4-D reduced the doses of pyraflufen-ethyl/2,4-D for 50, 80, and 95% GR horseweed control to 19, 46 and 201 g ha−1, respectively. Pyraflufen-ethyl/2,4-D + metribuzin controlled GR horseweed 97% which is comparable to the current industry standards. Based on these results, pyraflufen-ethyl/2,4-D + metribuzin (527 + 400 g ha−1) applied preplant can be used for GR horseweed control in soybean.

The Addition of Saflufenacil to Glyphosate plus Dicamba Improves Glyphosate-Resistant Canada Fleabane (Erigeron canadensis L.) Control in Soybean

“…Previous research reported similar results when pyraflufenethyl/2,4-D was tank-mixed with other herbicides for GRCF control. Westerveld et al [42] reported no benefit in GRCF control when adding low rates of pyraflufen-ethyl/2,4-D (≤132 g ai ha −1 ) to glyphosate (900 g ae ha −1 ) + metribuzin (400 g ai ha −1 ); however, GRCF control was improved by 20% when greater rates of pyraflufen-ethyl/2,4-D (≥527 g ai ha −1 ) were added to glyphosate (900 g ae ha −1 ) + metribuzin (400 g ai ha −1 ) at 2, 4 and 8 WAA. In contrast to the present study, Westerveld et al [42] observed 87 and 95% decreases in GRCF density and biomass, respectively, when pyraflufen-ethyl/2,4-D (527 g ai ha −1 ) was added to glyphosate (900 g ae ha −1 ) + metribuzin (400 g ai ha −1 ), compared to glyphosate (900 g ae ha −1 ) + metribuzin (400 g ai ha −1 ).…”

Improving the Level and Consistency of Glyphosate-Resistant Canada Fleabane (Erigeron canadensis L.) Control With Bromoxynil-Based Tankmixes Applied Preplant to Soybean

“…All other tankmixtures were considered additive. Westerveld et al (2021b) reported synergism when pyraflufen-ethyl/2,4-D (527 g ai ha -1 ) was added to glyphosate (900 g ae ha -1 ) plus metribuzin (400 g ai ha -1 ) applied PP in soybean 8 WAA.…”

Response of dry beans to tiafenacil applied preemergence

“…The suggested rate for tiafenacil use in dry bean crops is 25 to 75 g ai ha −1 . Westerveld (2021) reported comparable yield as the non-weedy plots with tiafenacil applied PP at 25 and 50 g ai ha −1 alone and in mixes with other herbicides in soybean. Similarly, another recent study has shown little injury with tiafenacil applied PP at 12.5, 25, and 37.5 g ha −1 in corn (Soltani et al 2021).…”

“…Tiafenacil is a new nonselective, pyrimidinedione, contact herbicide developed by FarmHannong Co., Ltd., in Korea, that is under consideration for use in corn, soybean, wheat, cotton, and other crops to control both monocot and dicot weeds prior to crop emergence (Anonymous 2020; Park et al 2018; Westerveld 2021). Tiafenacil is one of the most active protoporphyrinogen IX oxidase (PPO) inhibitor herbicides from the pyrimidinedione chemical family (Park et al 2018).…”