Research Showcase Gallery (Poster 2249)

Restoration Efforts for the Oregon silverspot butterfly: How do herbicides impact early blue violet biomass and consumers while exposed to invasive plant competition?

Abstract

Plant resources for at-risk butterflies are increasingly growing in stressful environments due to competition with invasive weeds. Selective herbicides are a sought-after tool by managers to reduce invasive plants, but impacts on butterflies are poorly understood. Although lethal and sub-lethal effects of herbicides have been examined for some species, few studies examine herbicide effects on larvae within the context of plant competition. The effects of one grass-specific herbicide (fluazifop-p-butyl) and one broadleaf-specific herbicide (clopyralid) were examined on host-plant violets, Viola adunca, grown in competition with tall fescue, Festuca arundinacea, and false dandelion, Hypochaeris radicata. Larvae of a surrogate species related to threatened Oregon silverspot butterfly, Speyeria zerene zerene, were raised on treated violets. Differences in violet biomass and Speyeria z. zerene pupal and adult biomass were assessed. Grown in competition, violet biomass was positively correlated with use of either herbicide in initial measurements. In final measurements, violet biomass was significantly different between those competitively grown, regardless of herbicide, and those grown without competition. Pupal and adult biomass were positively correlated with use of either herbicide when the violet was grown in competition. Both herbicide treatments produced greater pupal and adult biomass when compared to the untreated procedural control. Significant differences were found between pupae and adults reared on plants grown in absence of competition versus those reared on plants grown in competition and treated with fluazifop-p-butyl. These results imply that stress of competition may alter the quality of host-plants and herbicide use in managing at-risk butterfly habitats requires further examination.


About the Presenter

photo of Alyxandra James

Alyxandra James

Alyxandra is an avid outdoors person who chose to pursue an education in environmental science to help protect the natural areas she loves so much! She has been volunteering with the Schultz Conservation Biology lab over the past year studying the non-target effects of herbicides on threatened butterflies. Originally from Southern Oregon, Alyxandra graduates with a bachelor’s in environmental science this spring and returns to Oregon to execute old growth forest research in the summer of 2020. Alyxandra plans to pursue a master’s degree in environmental engineering at Oregon State University in coming years.