Document Type

Honors Project

Publication Date



One of the most threatened plants in the Great Lakes region is Pitcher’s thistle (Cirsium pitcheri), which inhabits sand dunes along the shorelines of Lakes Michigan, Huron, and Superior. In addition to risks from habitat loss and invasive species, C. pitcheri are imperiled by a thistle bud weevil (Larinus planus) that was originally distributed for biological control of nonnative thistles. During the summer of 2014, we empirically studied the devastating damage caused by L. planus on a population of C. pitcheri at Whitefish Dunes State Park, WI, to determine what factors influence the distribution and intensity of damage. We devised three treatments isolating the effects of elevation and neighboring plants. Our experiment revealed that the low elevation treatment with the greater neighboring plant density experienced the most damage during both the early and late season assessments. Additionally, we demonstrated that different abiotic and biotic factors affect L. planus distribution and damage during the early season compared to the late season. Finally, we analyzed the thistle-weevil system from a spatial ecology perspective. These results have important implications for other studies of plant-insect interactions, offer a cautionary tale about biological control, and inform efforts to conserve C. pitcheri.

Level of Honors

summa cum laude




Alyssa Hackes