Corn Research

Evaluation of a flexible weed management program for glyphosate tolerant corn
Dr. Clarence Swanton, University of Guelph

The objective of this project is to develop and evaluate the agronomic and economic performance of a flexible weed management strategy in corn. This weed management program will incorporated the strategic use of reduced rate pre-emergence herbicides with post-emergence herbicides on an “if-required” basis. The strategy will also improve the flexibility of weed management by widening the window for herbicide application. Furthermore, it aims to reduce the risk associated with weed management, optimize crop yields and profitability and provide the potential to reduce herbicide use.

In trials conducted in Woodstock and Elora in 2008, corn yields were generally greater when full or half rate residual herbicides were tank-mixed or followed by glyphosate than when applied alone. Optimal seasonal rainfall and other growing conditions minimized the impact of mid-late season weed interference on corn yields. For example, in Woodstock, the half rate of Aatrex alone provided 40 to 60 percent mid-season control of all weed species but yield was reduced by only 11 percent when compared to the weed-free treatment. Aatrex applied pre-emergence alone at half-rates followed by a sequential application of Roundup when corn was at the seven to eight leaf stage consistently provided superior weed control compared to full rate pre-emergence treatments of Aatrex, Aatrex plus Prowl H2O, and Primextra II Magnum.

The strategic use of reduced rate pre-emergence herbicides with post-emergence application of Roundup on an “if-required” basis improves the flexibility of weed management by widening the window for herbicide application and provides an opportunity to optimize weed management for weed control and corn yield and to reduce herbicide cost.

This project is supported through ORD.