The implications of light quality for weed control

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Cressman, Scott Tyler
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University of Guelph

Crop seedlings have the ability to detect the presence of neighbouring weeds by means of the R:FR ratio reflected from the weeds leaf surfaces. The role of the R:FR ratio as a weed management tool has not been explored. Laboratory experiments were conducted to test the following hypotheses: 1) the persistence of R:FR ratio reflected from the leaf surface of weeds treated with herbicides is dependent upon herbicide chemistry and dose, and 2) weeds species differ in their ability to reflect R:FR ratio and these differences are dependent on seedling growth, leaf area, and distance from the weed canopy. Results of this study confirm that the R:FR ratio reflected from the leaf surface of weeds is affected by: herbicide chemistry, herbicide dose, weed species, stage of weed development and distance of the weed from the crop. This information is of particular importance to herbicide selection and application timing of postemergence herbicides.

crop seedlings, weeds, weed management tool, red/far-red ratio, light quality, herbicide, leaf surface, reflection