title: Glyphosate and dicamba herbicide tank mixture effects on native plant and non-genetically engineered soybean seedlings.
abstract: Crops engineered to contain genes for tolerance to multiple herbicides may be treated with several herbicides to manage weeds resistant to each herbicide. Thus, nearby non-target plants may be subjected to increased exposure to several herbicides used in combination. Of particular concern are native plants, as well as adjacent crops which have not been genetically engineered for tolerance to herbicides. We evaluated responses of seven species of native plants grown in a greenhouse and treated less than field application rates of glyphosate and/or dicamba: Andropogon gerardii, Asclepias syriaca, Eutrochium purpureum, Oenothera biennis, Polyganum lapathifolium, Solidago canadensis and Tridens flavus, and non-herbicide resistant soybean (Glycine max, Oregon line M4). Herbicide concentrations were 0.03 or 0.1 × field application rates of 1122 g ha(-1) active ingredient (a.i) (831 g ha(-1) acid glyphosate) for glyphosate and 562 g ha(-1) a.i. for dicamba. In general, plant growth responses to combinations of glyphosate and dicamba were less than the sum of growth responses to the individual herbicides (i.e., antagonistic effect), primarily when one or both herbicides alone caused a large reduction in growth. E. purpureum, P. lapathifolium and S. canadensis were the most sensitive species to both herbicides, while A. gerardii was the most tolerant, with no response to either herbicide. The combinations of herbicides resulted in responses most similar to that from dicamba alone for G. max and from glyphosate alone for T. flavus. The results of this study indicated the need for more data such as effects on native plants in the field to assess risks to non-target plants from combinations of herbicides.
authors.affiliation: US Environmental Protection Agency National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th Street, Corvallis, OR, 97333, USA, olszyk.david@epa.gov.
authors.forename: David
authors.initials: D
authors.lastname: Olszyk
authors.forename: Thomas
authors.initials: T
authors.lastname: Pfleeger
authors.forename: E Henry
authors.initials: EH
authors.lastname: Lee
authors.forename: Milton
authors.initials: M
authors.lastname: Plocher
mesh_terms: D018556:Crops, Agricultural / Q000187:drug effects* / Q000254:growth & development; D003996:Dicamba / Q000737:chemistry / Q000633:toxicity*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000633:toxicity; D006540:Herbicides / Q000737:chemistry / Q000633:toxicity*; D018570:Risk Assessment / Q000379:methods; D036226:Seedlings / Q000187:drug effects; D013025:Glycine max / Q000187:drug effects / Q000254:growth & development; D000097797:Glyphosate
chemical_list: D003996:Dicamba; D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate
references.citation: Science. 1963 Jul 26;141(3578):362
references.pmid: 17815995
references.citation: Annu Rev Plant Biol. 2010;61:317-47
references.pmid: 20192743
references.citation: Science. 2007 May 25;316(5828):1185-8
references.pmid: 17525337
references.citation: Pest Manag Sci. 2009 Jan;65(1):19-26
references.pmid: 18785223
references.citation: Environ Sci Pollut Res Int. 2015 Jun;22(11):8010-21
references.pmid: 24728576
references.citation: Environ Toxicol Chem. 2007 Dec;26(12):2634-43
references.pmid: 18020679
references.citation: Ecotoxicology. 2012 Oct;21(7):1771-87
references.pmid: 22547211
references.citation: Ecol Appl. 2012 Mar;22(2):459-71
references.pmid: 22611847
references.citation: Environ Toxicol Chem. 2013 Nov;32(11):2542-51
references.pmid: 23881750
references.citation: Environ Pollut. 2014 Feb;185:295-306
references.pmid: 24316067
references.citation: Integr Environ Assess Manag. 2008 Jan;4(1):105-17
references.pmid: 17973566
references.citation: Environ Toxicol Chem. 2012 May;31(5):1023-31
references.pmid: 22362509
references.citation: Environ Toxicol Chem. 2009 Sep;28(9):1920-9
references.pmid: 19413364
references.citation: Environ Pollut. 2012 May;164:24-7
references.pmid: 22310058
references.citation: Pest Manag Sci. 2015 Mar;71(3):357-76
references.pmid: 25346235
references.citation: Environ Toxicol Chem. 2014 Mar;33(3):696-702
references.pmid: 24488525
references.citation: Ecotoxicology. 2004 May;13(4):349-69
references.pmid: 15344515
references.citation: Integr Environ Assess Manag. 2010 Oct;6(4):725-34
references.pmid: 20872651
references.citation: Pest Manag Sci. 2007 Mar;63(3):282-95
references.pmid: 17304633
references.citation: Sci Total Environ. 2012 Jan 15;415:79-92
references.pmid: 21621821