Student 10-Minute Presentation
Plant-Insect Ecosystems
Student
Student Competition
Olivia Bigham
Purdue University
Lafayette, Indiana
Tyler Dreaden
University of Kentucky
Lexington, Kentucky
James Jacobs
USDA-Forest Service
St. Paul, Minnesota
Matthew Ginzel
Professor & Director of the Hardwood Tree Improvement and Regeneration Center
Purdue University
West Lafayette, Indiana
Anna Conrad
Purdue University
Delaware, Ohio
Since 2019, sassafras trees in the Central Hardwood Forest Region have been wilting, yet the cause remains unknown. Initially, it was suspected that laurel wilt, a deadly disease of sassafras and other laurel species, had spread. However, neither its primary insect vector (Xyleborus glabratus) nor the causal agent of laurel wilt (Harringtonia lauricola) have been detected. However, investigations of material from wilting trees revealed two non-native ambrosia beetles (Xylosandrus germanus and X. crassiusculus) and a potentially novel fungus closely related to Ophiostoma quercus.
In this study, we conducted a series of field and greenhouse experiments to understand the etiology of wilt symptoms in sassafras. Over the last two years, we have conducted field surveys and enlisted private landowners and government agencies to report wilting trees to better understand the full range and progression of symptoms of this emerging threat to forest health. We are also characterizing the insect and microbial communities associated with wilting sassafras. To date, from symptomatic material several non-native ambrosia beetle species have been reared and a fungus closely related to the Ophiostoma found in 2019 was isolated. Additionally, to fulfill Koch’s postulates, we tested the pathogenicity of this fungus to determine its role in causing wilt symptoms. This work is crucial to understanding the cause of sassafras wilt and developing effective strategies to safeguard this important native understory tree species.