ARS | Publication request: Sweet corn hybrid influences outcomes of wild proso millet suppression with sethoxydim

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract
Publication Acceptance Date: January 15, 2007
Publication Date: February 5, 2007
Citation: Williams, M., Boydston, R.A. 2007. Sweet corn hybrid influences outcomes of wild proso millet suppression with sethoxydim [abstract]. Weed Science Society of America Meeting Abstracts. Paper No. 121.

Technical Abstract: he extent to which crop interference can reduce reliance on other forms of weed control are poorly known. Observed variation in weed suppressive ability among sweet corn hybrids, coupled with the need for new approaches to manage annual grasses, provide incentive to quantify the effect of crop hybrid on efficacy of sethoxydim doses. A split plot design was established in Urbana, Illinois and Prosser, Washington in 2005 and 2006 where main plot treatments were one of two sethoxydim-tolerant sweet corn hybrids, also seeded with wild proso millet. Subplot treatments received doses of sethoxydim ranging from 0 to 100 g ai/ha applied at 3-4 leaf wild proso millet. Percent weed control at 14 and 28 days after treatment (DAT) was similar between hybrids, with the dose resulting in 50% control ranging from 24 to 36 g ai/ha at 14 DAT and 28 to 43 g ai/ha at 28 DAT. However, as the season progressed, differences in sweet corn canopy density and weed suppressive ability among hybrids were observed. `Rocker¿ grew 26 to 37% taller than `Cahill¿, produced 20 to 120% more leaf area, and intercepted up to 26% more light. By the time of crop harvest, wild proso millet was suppressed to a greater extent by `Rocker¿, compared to `Cahill¿, over a range of sublethal doses, but not at 100 g ai/ha since control was complete in both hybrids. For instance in the absence of sethoxydim, wild proso millet biomass was suppressed 42 to 53% in Illinois and 24 to 34% in Washington by `Rocker¿, relative to `Cahill¿. This study demonstrates that outcomes of sublethal herbicide dose application depend in part on the extent of crop interference provided by sweet corn hybrid. More competitive sweet corn hybrids, as determined by canopy density, may increase herbicide efficacy under sub-optimal conditions, enhance the success of reduced herbicide doses, or contribute to weed management in organic cropping systems.