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Title: Efficacy of Topramezone and Tembotrione Herbicides in Sweet Corn: Effect of Atrazine Rate, Adjuvants, and Timing

Author
item PEACHEY, E - OREGON ST UNIV
item Williams, Martin
item Boydston, Rick

Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2007
Publication Date: 7/21/2008
Citation: Peachey, E., Williams, M., Boydston, R.A. 2008. Efficacy of Topramezone and Tembotrione Herbicides in Sweet Corn: Effect of Atrazine Rate, Adjuvants, and Timing. Western Society of Weed Science Meeting Proceedings. 61:36.

Interpretive Summary:

Technical Abstract: Experiments determined the effect of soil residual tankmix, atrazine rate, and adjuvant on control of wild proso millet and other broad leaf weeds with topramezone and tembotrione. Topramezone (18 g ai/ha) and tembotrione (92 g/ha) were applied as a tankmix with dimethenamid-P plus atrazine (0.95 + 0.56 kg ai/ha) or S-metolachlor plus atrazine (1.6 + 0.56 kg ai/ha) to V2 or V4 corn. Leaf burn of corn was observed in both years of the study, and was most prominent for tankmixes with S-metolachlor in 2007 and with dimethenamid-P in 2006. Higher temperatures in 2006 at the time of the dimethenamid-P application may have predisposed corn to injury and reduced yield. Weed control was better and crop yield greater when these treatments were applied at V2 rather than V4, particularly at sites with a high weed density. Additional treatments evaluated the impact of methylated seed oil (0.25% or 1% v/v) and urea ammonium nitrate (0 or 2.5% v/v) on topramezone and tembotrione efficacy. Weed control improved substantially for both herbicides when the MSO rate increased from 0.25% to 1%, with slight differences in efficacy between tembotrione and topramezone depending on weed species present. In Oregon, tembotrione (92 g/ha) and topramezone (18 g ai/ha) were applied to hybrid Super Sweet Jubilee with 123, 370, or 1120 g ai/ha of atrazine to determine the most efficient rate of atrazine. Both weed control and corn yield declined as the atrazine rate was reduced from 1120 to 123 g ai/ha. An exception to the trend was apparent when tembotrione was applied without atrazine. Yields of tembotrione and topramezone treatments without atrazine were similar to yields when tankmixed with 1120 g/ha atrazine, probably because the number of ears harvested increased when the two HPPD herbicides were applied without atrazine. A similar study was conducted that included sites in Illinois and Washington. Tembotrione (31 g ai/ha) was applied with 0, 42, 123, 370, or 1120 g ai/ha of atrazine to varieties Code 128 and Quickie. On average, the variety Quickie was 115 cm tall and intercepted 70% of the available PAR at silking. Code 128 was 221 cm tall and intercepted 91% of the available PAR. Weed control declined as the atrazine rate declined, but only in the less competitive variety Quickie, and only at the site with the greatest weed density.