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United States Department of Agriculture

Agricultural Research Service

Title: Synergistic Effects of a Combined Exposure to Herbicides and An Insecticide in Hyla Versicolor

Authors
item Mazanti, L - USDA/NRCS
item Sparling, D - USGS
item RICE, CLIFFORD
item BIALEK KALINSKI, KRYSTYNA
item Stevenson, C - UNIV MD
item Teals, B - USDA/NRCS

Submitted to: Book Chapter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 22, 2002
Publication Date: N/A

Interpretive Summary: Pesticide combinations were tested under both laboratory and field conditions to determine their individual and combined effects on amphibian populations. In the lab, tadpoles of the gray treefrog experienced 100% mortality when exposed to a high but environmentally realistic pesticide combinations whereas low concentrations of the pesticides or high concentrations of either herbicides or insecticides caused non-lethal effects of lethargy, reduced growth and delayed metamorphosis but no significant mortality. In some pesticide combinations, significantly reduced amphibian populations were observed compared to controls whereas with other combinations amphibian populations were able to rebound through recruitment by the end of the season. This information will be useful in assessing the toxicity of edge-of field runoff and as input for determining the environmental standards, such as TMDLs (Total Maximum Daily Loads).

Technical Abstract: Combinations of the herbicides, atrazine and metolachlor, and the insecticide chlopyrifos were tested under both laboratory and field conditions to determine their individual and combined effects on amphibian populations. In the lab, Hyala versicolor tadpoles experienced 100% mortality when exposed to a high but environmentally realistic combination of pesticides. Low concentrations of the pesticides or high concentrations of either herbicides or insecticide caused sublethal effects of lethargy, reduced growth and delayed metamorphosis but no significant mortality. In the field with macrocosms, high herbicide-low insecticide and low herbicide-low insecticide mixtures significantly reduced amphibian populations compared to controls. However, in the low herbicide-low insecticide treatments, amphibian populations were able to rebound through recruitment by the end of the season. This information will be useful in assessing the toxicity of edge-of field runoff and as input for determinin TMDLs (Total Maximum Daily Loads).

Last Modified: 9/29/2014
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