Ambrosia beetle symbioses & threats to forest health


  • Characterizing novel symbiotic associations from diverse environmental microbial samples.
  • Developing sampling and analytical tools for rapid identification of symbiotic associations that pose serious risks to global forest health.

Bark and ambrosia beetles are simultaneously associated with commensal, parasitic, and mutualistic fungal taxa that form complex fungal communities within the beetles and their galleries (Figure 8). While most of these beetle associated fungi are harmless, a few are virulent plant pathogens that threaten global forest health and agriculture; e.g. laurel wilt disease, Dutch elm disease, and thousand cankers disease which have decimated American red bay, American and European elms, and American walnuts respectively. Invasions of beetles carrying these pathogens have caused irreparable damage to naïve ecosystems and caused hundreds of millions of dollars in damages. Consequently, there is a need for efficient and effective methods to rapidly and accurately identify associations between beetle and potentially threatening fungal taxa.


As part of the Emerging Threats to Forests Research Group (, I am using traditional culture techniques, sequence-based taxonomy, and new molecular sampling techniques via direct meta-barcode sequencing of DNA and RNA to rapidly characterize the fungal communities associated with known invasive and potentially invasive beetle species at home and abroad. These incredibly rich datasets are then combined with powerful multivariate and permutations-based statistical analyses to identify significant associations between beetle and fungal species (Figure 9). Potentially pathogenic fungi that are found to be significantly associated with beetles are then tested for pathogenicity in American pines and oaks. Using these methods, we have sampled in 8 countries throughout Asia and Europe, isolated nearly one thousand fungi from 243 beetle species, discovered multiple novel associations between beetle and fungal lineages, and tested dozens of potentially pathogenic beetle associated fungal isolates.



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Brood chamber of an ambrosia beetle (Xylosandrus discolor) containing beetle eggs and luscious ambrosia fungus that was inoculated and cultured by an adult female.

Ambrosia beetles have interesting mating systems. These Xyleborus pinicola are haplo-diploid. The horned male is a flightless, blind, haploid whom mates with his diploid sisters immediately after pupating and just before the females disperse.

Fungal symbiont isolated from X. pinicola in Southeast Asia. Could this fungal symbiont be the next major threat to american forest health? We are working hard to find out!