Sap Beetles (Coleoptera: Nitidulidae) in Oak Forests of Two Northeastern States: A Comparison of Trapping Methods and Monitoring for Phoretic Fungi

Oak wilt is slowly expanding in the northeastern United States. Several nitidulid beetle species are known vectors of the fungus [Bretziella fagacearum(Bretz) Z. W. De Beer, Marinc., T. A. Duong, and M. J. Wingf (Microascales: Ceratocystidaceae)] that causes this disease, acquiring spores from fungal mats on infected trees and transmitting them to uninfected trees. Survey and fungal isolation from captured nitidulid beetles could be an important tool for detecting the presence of this disease in a geographic area not previously known to have oak wilt. In preparation for monitoring activities in such areas, two trapping studies were conducted in the northeastern United States: 1) trap test comparing the efficacy of wind-oriented pipe, multiple-funnel, and modified pitfall traps for nitidulids and 2) wet and dry collection cup comparison. Lures were a combination of nitidulid pheromones and fermenting liquid. Results support the use of multiple-funnel traps over the other two trap types, for both targeted species-specific surveys and community sampling. More total nitidulids, Colopterus truncatus(Randall), and Glischrochilus fasciatus(Olivier) were captured in wet collection cups compared with dry cups. Twenty-seven fungal species were isolated, none of which were B. fagacearum. Many fungi isolated from beetles were plant pathogens, indicating that in addition to the oak wilt fungus, sap beetles may contribute to the spread of other plant diseases.