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1 January 2011 Native Grass and Forb Response to Pre-Emergent Application of Imazapic and Imazapyr
Matt A. Bahm, Thomas G. Barnes
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Grassland restoration attempts to rehabilitate and/or re-create biologically diverse native plant communities using a variety of management techniques including seeding, burning, grazing, and most recently using herbicides. Herbicides are an important tool for suppressing weed competition for initial seedling growth and removing exotic species in native plant communities. Little information is available on which species of native plants can endure a pre-emergent application of the imidazolinone herbicides. In spring 2006, we initiated a study testing responses of three native grasses and three native forbs to pre-emergent treatments of 0.035 kg ai/ha imazapic, 0.07 kg ai/ha imazapic, and 0.07 kg ai/ha imazapyr. Seedling establishment was monitored at 5 and 14 months after treatment and weed cover was monitored at 2.5, 5 and 14 months after treatment. There were no differences in the number of seedlings found in the untreated plots compared to all the herbicide-treated plots and there were no differences in seedling densities of green needlegrass (Nassella viridula) with the exception of the high imazapic treatment. Showy tick trefoil (Desmodium canadense) and Canada milk vetch (Astragalus crassicarpus) also appear to be able to tolerate applications of all herbicide treatments. There was less weed cover in the herbicide-treated plots when compared to the untreated control plots. This information provides managers options to include these species in initial seeding or restoration projects using these herbicides which may increase diversity and reduce restoration projects cost in the long term.

Matt A. Bahm and Thomas G. Barnes "Native Grass and Forb Response to Pre-Emergent Application of Imazapic and Imazapyr," Natural Areas Journal 31(1), 75-79, (1 January 2011).
Published: 1 January 2011

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