Canada fleabane (Conyza canadensis) control with preplant applied residual herbicides followed by 2,4-D choline/glyphosate DMA applied postemergence in corn

Abstract

Ford, L., Soltani, N., Robinson, D. E., Nurse, R. E., McFadden, A. and Sikkema, P. H. 2014. Canada fleabane (Conyza canadensis) control with preplant applied residual herbicides followed by 2,4-D choline/glyphosate DMA applied postemergence in corn. Can. J. Plant Sci. 94: 1231–1237. Glyphosate resistant (GR) Canada fleabane (Conyza canadensis) is an extremely problematic weed in no-tillage farming operations. A total of five field trials were conducted over a 2-yr (2012 and 2013) period in Ontario to determine the level of GR Canada fleabane control with a two-pass weed control program of a pre plant (PP) residual herbicide followed by 2,4-D choline/glyphosate dimethylamine (DMA) applied POST. Among residual herbicide treatments evaluated, s-metolachlor (1600 g a.i. ha−1)+flumetsulam (50 g a.i. ha−1)+clopyralid (135 g a.e. ha−1) provided the most consistent (95–99%) control across all sites 8 wk after application (WAA). S-metolachlor/atrazine (1800 g a.i. ha–1) did not provide effective GR Canada fleabane control (21–86%) 8 WAA. The preplant residual herbicides followed by 2,4-D choline/glyphosate DMA (1720 g a.e. ha−1) POST provided 97–100% control. Glyphosate (900 g a.e. ha−1) applied PP followed by 2,4-D choline/glyphosate DMA POST provided 80–93% control 8 WAA. The application of 2,4-D choline/glyphosate DMA POST following any PP residual herbicide resulted in 97% or greater control of GR Canada fleabane. Results from this research demonstrate that residual herbicides applied PP followed by 2,4-D choline/glyphosate DMA POST provides excellent control of GR Canada fleabane, and also incorporates different modes of action thereby limiting the selection of resistant weeds.