Effects of Herbicides on Behr’s Metalmark Butterfly, a Surrogate Species for the Endangered Butterfly, Lange's Metalmark

This experiment evaluated the effects of herbicides on the Behr’s metalmark butterfly (Apodemia virgulti Behr) as a surrogate for the imperiled Lange’s metalmark butterfly (Apodemia mormo langei). Behr’s metalmark first instars were exposed to field rates of triclopyr (Garlon 4 Ultra), sethoxydim (Poast), and imazapyr (Stalker) to determine their effects. 

The herbicides were applied at their recommended field rate directly to the first instars and their food, with water applied for controls. Larvae were fed plants that had been treated with the herbicides after they consumed their initial food. Exposure to triclopyr, sethoxydim, and imazapyr all resulted in significant reductions in the number of pupae produced and thus the number of adults that emerged. 

Since each herbicide has a different mode of action, the authors suspect that the effects are due to inert ingredients or indirect effects on food plant quality. If they have the same effects on the Lange’s metalmark, they could contribute to the decline of the species. The authors note that the use of herbicides in restoration and natural areas should be carefully considered, especially for projects in endangered butterfly habitat. 

Authors: 
Stark, John D., Xue Dong Chen, and Catherine S. Johnson
Journal: 
Environmental Pollution
Year published: 
2012