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RESEARCH REPORT: USE OF VEGETATIVE VIGOR TEST TO DETECT EFFECTS OF LOW LEVELS OF HERBICIDES ON SELECTED NON-CROP PLANTS
Citation:
OLSZYK, D. M., M. BLAKELEY-SMITH, T. G. PFLEEGER, E. LEE, G. KING, M. PLOCHER, AND J. KERN. RESEARCH REPORT: USE OF VEGETATIVE VIGOR TEST TO DETECT EFFECTS OF LOW LEVELS OF HERBICIDES ON SELECTED NON-CROP PLANTS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/117, 2006.
Impact/Purpose:
To improve phytotoxicity testing protocols
Description:
To address the need for improved phytotoxicity testing protocols, we evaluated use of the vegetative vigor test methodology for use in determining effects of low concentrations of chemical herbicides on terrestrial non-crop plant species. Species included native plants from Illinois in the corn-soybean belt in the Midwestern U.S., for comparison with crops, and native and introduced plants from the Willamette Valley of Oregon. Two native species; Polygonum lapathifolium and Solidago canadensis had EC25 values for reductions in shoot dry weight of 0.0003 to 0.0016 x f.a.r. (active ingredient) of sulfometuron methyl (sulfometuron), which was within the same range of 0.0002 to 0.0017 x f.a.r. for the crop species Avena sativa, Daucus carota, Glycine max, Solanum lycopersicon, and Zea mays. The other native species Andropogon gerardii and Tridens flavus were most resistant to sulfometuron whereas Symphyotrichum lateriflorum was intermediate in sensitivity. In the Willamette Valley prairie plant study there was a wide variety of responses among 17 species (14 native and 3 introduced) to each herbicide tested [glyphosate, tribenuron methyl (tribenuron) or fluazifop-P-butyl (fluazifop)]. For glyphosate, Potentilla gracillis was the most sensitive species based on an EC25 value of 0.012 x f.a.r. for dry weight; while Bromus carinatus, Clarkia amoena, Gilia capitata, and Lupinus albicaulis were resistant to glyposate as indicated by no effect on dry weight. Seven Willamette Valley forb (broadleaf herbaceous plant) species were sensitive to tribenuron based on EC25 values of 0.001 to 0.012 x f.a.r. for reductions in shoot dry weight; Clarkia amoena, Collinsia grandiflora, Leucanthemum vulgare, Potentilla gracilis, Prunella vulgaris, Ranunculus occidentalis and Sanquisorba occidentalis. Six grass species and Eriophyllum lanatum were resistant to tribenuron showing no reduction in dry weight. Fluazifop primarily affected grass species as expected due to the grass-specific activity for this herbicide. Two native grasses, Elymus trachycaulus and Danthonia californica were the most sensitive to fluazifop, based on low EC25 values of 0.002 to 0.010 x f.a.r. for shoot dry weight. A native fescue grass, Festuca roemeri, and nearly all the forb species were resistant to fluazifop, showing no response for any parameter at any herbicide rate. The results from this research will be useful as background information for evaluating potential modifications in the EPA's Series 850.4150 Vegetative Vigor Test to assess the risk of chemical herbicides to non-target plants. The results also indicate the potential to use herbicide dose / plant response data to favor the growth of species of interest while inhibiting the growth of undesirable species (usually introduced and/or invasive species) which are sensitive to specific herbicides. For example, the three introduced species in the Willamette Valley study were sensitive to different herbicides glyphosate (Festuca arundinacea), fluazifop (Cynosurus echinatus) and tribenuron (Leucanthemum vulgare), respectively.