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Response of Pennsylvania native plant species to dicamba and/or glyphosate
OLSZYK, D. M., T. G. PFLEEGER, T. Griffin, E. LEE, AND M. PLOCHER. Response of Pennsylvania native plant species to dicamba and/or glyphosate. Presented at Weed Science Society of America Annual Meeting & Trade Show, Denver, CO, February 07 - 11, 2010.
Weeds may become resistant to intensive and extensive use of specific herbicides associated with the growth of herbicide tolerant crops, e.g., the use of glyphosate for weed control with glyphosate tolerant soybeans.
Weeds may become resistant to intensive and extensive use of specific herbicides associated with the growth of herbicide tolerant crops, e.g., the use of glyphosate for weed control with glyphosate tolerant soybeans. To counter this resistance, crops modified to contain genes for tolerance to both glyphosate and dicamba may be treated with both herbicides to control weeds tolerant to either herbicide. Thus, non-target plants may be subjected to aerial drift from two herbicides used in combination, instead of just one. Of particular concern are non-target native plants which provide resources for wildlife, however, crops which have not been genetically modified for tolerance to both herbicides may also be at risk. We evaluated the response of eight species on native plants found in Lancaster County, Pennsylvania to glyphosate and/or dicamba: Andropogon gerardii, Asclepias syriaca, Eupatorium pupureum, Oenothera biennis, Polyganum lapathifolium, Solidago canadenses and Tridens flavus. We also grew non-herbicide resistant soybean (Glycine max, Oregon cultivar14), which may be at risk from drift of glyphosate and dicamba used on tolerant soybeans. Herbicide concentrations representing aerial drift were used, 0.1 or 0.03 x field application rates of 830 and 563 g HA-1 for glyphosate and dicamba, respectively. Plants were grown in a greenhouse using a modification of EPA’s vegetative vigor testing protocol. In general, glyphosate or dicamba individually reduced plant growth; with the effects of the combined herbicides being species dependent. The results of this study are discussed in terms of assessments of risks to non-target plants from combinations of herbicides.