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

Abstract

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.

Early detection of the oak wilt fungus (Bretziella fagacearum) using trapped nitidulid beetle vectors

“…The beetles collected in wet collection traps were not used for culturing due to the sterilizing ability of the propylene glycol commonly used in wet trapping systems. The results showed that multiple‐funnel trap with wet collection cups caught higher abundances and more diverse groups of nitidulids in New York (DiGirolomo et al, 2020).…”

“…New York began trapping nitidulid beetles in 2017 as part of a multi‐state effort to determine (1) which trap types collected the highest abundance and diversity of nitidulid beetles and (2) to determine if oak wilt could be cultured from beetles collected in wind‐oriented dry collection traps (DiGirolomo et al, 2020). Oak wilt was not successfully cultured from dry‐collected beetles during the study.…”

“…The beetles are also attracted to sap from tree wounds, and as they feed in the wounds, the spores can be deposited and cause new infections. Fungal spore mats have been found most abundantly in spring and fall in other parts of the disease range (Juzwik et al, 2011) highest abundance and diversity of nitidulid beetles and (2) to determine if oak wilt could be cultured from beetles collected in windoriented dry collection traps (DiGirolomo et al, 2020). Oak wilt was not successfully cultured from dry-collected beetles during the study.…”

New records of Nitidulidae (Nitidulidae, Coleoptera) species in Canada, Ontario, and Manitoba

“…Flying beetles were collected using four types of traps; wind-oriented funnel traps, 12-unit Lindgren funnel traps, 12-unit modified Lindgren funnel traps, and 5-unit Synergy multitraps (Synergy Semiochemical Corp. Delta, BC ). Wind-oriented funnel traps are also referred to as PVC pipe traps and wind-oriented pipe traps ( Dowd et al 1992 ; DiGirolomo et al 2020 ). Three traps were placed at least 10 m apart at 16 localities in Ontario and Manitoba.…”

“…Oak trees are susceptible to this fungus with some species dying within weeks of the initial infection. Oak wilt can infect neighboring trees through root-to-root contact ( Bruhn et al 1991 ), however transmission by nitidulids is considered more concerning because of the potential for transmission over greater distances and the formation of many new infection epicenters ( DiGirolomo et al 2020 ).…”