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Development of a constructed Willamette Valley plant community to determine non-target effects of herbicide drift on native plants
Citation:
Olszyk, D., T. Pfleeger, T. Shiroyama, AND Milt Plocher. Development of a constructed Willamette Valley plant community to determine non-target effects of herbicide drift on native plants. Presented at SETAC, Nashville, TN, November 17 - 21, 2013.
Impact/Purpose:
As part of its regulation of pesticides, the US Environmental Protection must consider potential environmental effects, including impacts to nontarget plants. Normally the Office of Pesticides Programs (OPP) risk assessment to determine these impacts requires simple, individual species, greenhouse, dose-response experiments with growth endpoints. The study demonstrated a useful experimental protocol whereby a plant community can be evaluated for ecological responses, and will provide information which OPP can use in requesting field test to determine ecological responses to pesticides. The field test included small (0.45 x 0.45 m) plots planted with nine perennial Willamette Valley native plant species: Eriophyllum lanatum (Oregon sunshine), Iris tenax (Toughleaf Iris), Prunella vulgaris var. Lanceolata (Self-Heal), Camassia leichtlinii (Large Camas), Festuca roemeri (Roemer’s fescue), Elymus glaucus (Blue wildrye), Ranunculus occidentalis (Western Buttercup), Frageria virginiana (Virginia/wild strawberry), and Potentilla gracilis (Slender Cinquefoil). Plots were established on two Oregon State University farms. The effects of aminopyralid and fluroxypyr, alone and in combination, were determined at 0.03 and 0.1 x a Field Application Rate (FAR) of 10.4 grams active ingredient (g.a.i.) for aminopyralid and 147.1 g.a.i. for fluroxypyr. Response endpoints per species were % cover on a periodic basis, # of reproductive structures and seed production. The results suggest that field plots such as these can provide necessary information for ecological risk assessment.
Description:
As part of its regulation of pesticides, the US Environmental Protection must consider potential environmental effects, including impacts to nontarget plants. Normally the risk assessment to determine these impacts requires simple, individual species, greenhouse, dose-response experiments with growth endpoints. However, the extrapolation of potential risk of pesticide drift from individual species to a plant community should be viewed with caution. More sophisticated field tests may be required, but are rarely conducted. To provide a procedure for a field test to indicate herbicide effects on plant communities, we developed a series of small (0.45 x 0.45 m) plots planted with nine perennial Willamette Valley native plant species: Eriophyllum lanatum (Oregon sunshine), Iris tenax (Toughleaf Iris), Prunella vulgaris var. Lanceolata (Self-Heal), Camassia leichtlinii (Large Camas), Festuca roemeri (Roemer’s fescue), Elymus glaucus (Blue wildrye), Ranunculus occidentalis (Western Buttercup), Fragaria virginiana (Virginia/wild strawberry), and Potentilla gracilis (Slender Cinquefoil). Plots were established on two Oregon State University farms. One year after establishment of the plots, the effects of aminopyralid and fluroxypyr, alone and in combination, were determined at 0.03 and 0.1 x a Field Application Rate (FAR) of 10.4 grams active ingredient (g.a.i.) for aminopyralid and 147.1 g.a.i. for fluroxypyr. Response endpoints per species were % cover on a periodic basis, # of reproductive structures and seed production. The study demonstrated a useful experimental protocol whereby a plant community can be evaluated for ecological responses. However, there was little if any response to the herbicides for any species at either site in this study, possibly due to the large size of the plants and low levels of herbicides used.