Herbicide mixtures at reduced rates for effective weed control and herbicide resistance prevention in soybeans

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Little, Robin Marguerte Irene
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University of Guelph

Mixtures of herbicides are recommended to prevent resistance but are not easily implemented. Using mixtures to prevent resistance is widely used with other pests or pathogens. Triple therapies are used when the causal organism is resistance prone. The aim of this study was to determine whether a combination therapy approach is feasible by comparing a mixture of imazethapyr, pendimethalin, metribuzin, linuron, and metolachlor each at 1/3 the full rate, compared to standard soybean herbicides. Experiments were conducted at three sites in 2003 and 2004 and a total of 20 weed occurrences were evaluated. The combination of five herbicides at reduced rate provided similar level of control as the standards in 16 out of the 20 weed species/site/year occurrences and had no crop phytotoxic effect. The effectiveness of the combination was generally due to the combined action of all components and not to one component retaining high activity despite dose reduction.

resistance, combination therapy approach, mixture, imazethapyr, pendimethalin, metribuzin, linuron, metolachlor, herbicide, soybean herbicides