Pathology of the Green-Flowered Milkweed (Asclepias viridis) and Its Relationship to Arthropods and Monarch Butterfly (Danaus plexippus) Survivorship

Document Type


Degree Name

Master of Science (MS)


Biological and Environmental Sciences

Date of Award

Fall 2018


Monarch butterfly populations have exhibited sharp declines and understanding the cause of these declines is needed to support recovery efforts. There is no information about how the health and quality of Asclepias viridis host plants affect monarch larval survivorship. The purpose of this study was to examine the relationship between monarch host plant pathology and survival. Among the 11 pathologies, herbivory, yellowing, and leaf spot were most common. Plant pathology was unrelated to soil chemistry and viruses were the most likely cause of many symptoms, likely transmitted by milkweed herbivores. Based on an overall index of plant health, monarch survival was highest on plants with slight symptoms of pathology. Monarch survivorship was greater on plants with more ramets. Overall, the health and quality of milkweed host plants played a remarkably slight role in monarch survival. Land management should focus on maintaining stable populations of milkweed plants embedded in healthy and diverse plant communities to promote greater monarch survivorship.


Jeffrey G. Kopachena

Subject Categories

Life Sciences | Plant Sciences