Pine-specific beetle-fungus symbioses in Asia that have not yet invaded the US: empirical assessment of threat
J. HULCR (1), C. Bateman (1), W. Bo (2). (1) University of Florida, Gainesville, FL, U.S.A.; (2) Chinese Academy of Sciences, Xishuangbanna, China
Introduced tree diseases vectored by wood borers nearly eradicated a number of American tree species, including elms and redbays, and are now threatening crops such as walnuts or avocados. A similar future epidemic of American pines would result in an unprecedented disaster. We developed a safe and feasible approach for assessing the threat of exotic pine boring insects associated with fungi before their establishment in the US. Our data will enable federal agencies to distinguish harmless from actionable species in case of introduction. Our screening consists of five steps: 1) Collect target species abroad, using bait trees and traps. 2) Isolate fungal associates (potential pathogens); the vectors are discarded. 3) Fungal isolates are shipped to the US. 4) Assemble genotypes of each of the 3 most important pines in the SE US: loblolly, slash, and longleaf. 5) Each pine genotype is inoculated with each fungus to test for pathogenicity. Pathogenicity is fitted to one of three models of interactions between exotic beetle-borne tree pathogens and American trees: 1) no effect, 2) locally pathogenic, 3) systemic pathogens. The screening approach has been successfully tested in 2013 in China. It yielded data for three beetle-fungus complexes: Fungi of <i>Tomicus minor</i>: no pathogenicity; fungi of <i>Xyleborus pinicola</i>: no pathogenicity; fungi of <i>Ips chinensis</i>: mildly pathogenic to loblolly pine, should be monitored if detected. None of the three species is an imminent threat.
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