Herbicide effects on the endangered Lange's metalmark butterfly, Apodemia mormo langei, in the Antioch Dunes National Wildlife Refuge, California

The Lange’s metalmark butterfly (Apodemia mormo langei) is in imminent danger of extinction due to the loss of its habitat caused by invasive exotic plants which are eliminating naked stem buckwheat (Eriogonum nudum var. auriculatum), its food plant. The butterfly was listed as an endangered species on June 1, 1976 (Federal Register 41: 22141-22044). Invasive plants significantly impact the few remaining acres of habitat at the Antioch Dunes National Wildlife Refuge. Plant control measures include mowing, hand pulling, fire, and herbicides. In March 2007, the Recovery Branch of the Sacramento Fish and Wildlife Office asked the Environmental Contaminants Division to design experiments to test effects of herbicide treatments on larvae of other subspecies of metalmark butterflies. In this study, we evaluated the effects of three herbicides commonly used in the Antioch Dunes for weed control. The effects of Triclopyr (Garlon 4 Ultra), Sethoxydim (Poast), and Imazapyr (Stalker) on a surrogate species, Behr’s Metalmark, Apodemia virgulti were evaluated over the life-span of this species. The effects of these herbicides on Behr’s Metalmark will be discussed in relation to potential impacts on Lange’s metalmark.