DEC’s Forest Health Research Lab recently conducted a study to understand how far nitidulid beetles—native, sap-feeding beetles that spread oak wilt disease—can travel in forested environments. Oak wilt is a fungal disease that can kill oak trees within months. After a tree is killed by oak wilt, the fungus produces a sweet-smelling spore pad which attracts nitidulid beetles. The beetles become covered in spores while feeding, then carry the spores to new oak trees. The spores enter oak trees through wounds in the bark, causing a new infection.
While we know that nitidulid beetles spread the oak wilt fungus, it is unknown how far these beetles typically fly in a forested environment. To better understand flight distances of nitidulids, researchers at DEC’s Forest Health Research Lab collected nitidulid beetles in the woods, then brought them to the lab where they were dusted with a fluorescent powder. The powdered beetles were then released back in the woods at locations surrounded by rings of traps. Once a powdered beetle was collected in a trap, the team calculated the distance from the trap to the release point to tell how far it flew. The samples are still being processed, but early results indicate that some species can fly at least a half mile.
The team was also interested in which nitidulid species would commonly visit fresh oak wounds in New York. Previous years of trapping have revealed that New York is home to at least 44 species of nitidulid beetles. While rainy and cold weather dampened the study efforts, they did find that one species, Epuraea corticina, repeatedly visited wounds. Better understanding what species visit oak wounds will help determine which nitidulids may move oak wilt spores in New York.
Small, black beetles covered in bright pink fluorescent powder walk across a white surface.
Nitidulid beetles covered in fluorescent powder.
You can help prevent the spread of oak wilt by following these tips:
• Report sightings of oak wilt anywhere in New York state. If you see oak leaves turning brown and dropping during July-August, email foresthealth@dec.ny.gov with the location and photos or use our Forest Health Reporting form. Symptoms are most severe in red oaks, where more than half of the canopy can be lost. Symptoms in white oaks tend to be less severe, with trees typically only losing a few branches of discolored leaves per year.
• Only prune oak trees in October-February. Nitidulid beetles are most active in the spring and summer, so pruning only in the fall and winter months lowers the risk of spreading the disease.
• Follow regulations in oak wilt quarantine districts. Oak wilt quarantine districts prevent the spread of oak wilt by prohibiting the movement of potentially infected oak wood. Also remember to follow New York State’s Firewood Regulation everywhere in the state to prevent the spread of forest pests and diseases.
