No rest for the laurels: symbiotic invaders cause unprecedented damage to southern USA forests

Laurel wilt is an extraordinarily destructive exotic tree disease in the southeastern United States that involves new-encounter hosts in the Lauraceae, an introduced vector (Xyleborus glabratus) and pathogen symbiont (Raffaelea lauricola). USDA Forest Service Forest Inventory and Analysis data were used to estimate that over 300 million trees of redbay (Persea borbonia sensu lato) have succumbed to the disease since the early 2000s (ca 1/3 of the pre-invasion population). In addition, numerous native shrub and tree species in the family are susceptible and  threatened in the Western Hemisphere. Genetic markers were used to test the hypothesis that the vector and pathogen entered North America as a single introduction. With a portion of the cytochrome oxidase I gene, a single Xglabratus haplotype was detected in the USA. Similarly, Amplified Fragment Length Polymorphisms indicated that 95% (54 of 57) of the isolates of Rlauricola that were examined were of a single clonal genotype; only minor variation was detected in three polymorphic isolates. Similar levels of disease developed after swamp bay (Ppalustris) was inoculated with each of the four genotypes of Rlauricola. It is proposed that a single founding event is responsible for the laurel wilt epidemic in the United States.

Biological Invasions, July 2017, Volume 19, Issue 7, pp 2143–2157

Cold tolerance range of Redbay Ambrosia Beetle overlaps range of Sassafras albidum.

Formby, J.P., Rodgers, J.C., Koch, F.H. et al. Biol Invasions (2017).

Native Lauraceae (e.g. sassafras, redbay) in the southeastern USA are being severely impacted by laurel wilt disease, which is caused by the pathogen Raffaelea lauricola T. C. Harr., Fraedrich and Aghayeva, and its symbiotic vector, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff). Cold temperatures are currently the only viable limitation to the establishment of X. glabratus in northern populations of sassafras…

 

Visit to Torreya State Park

High above the Apalachicola River, in 1833 H.B. Croom discovered a rare native conifer.  Torreya taxifolia is named for the eminent American botanist John Torrey, and the current range only extends through 3 counties on the Florida-Georgia border. It is estimated that 99% of the population has been lost in the past century, most likely from a fungal pathogen that kills the mature tree and stunts and retards new growth. No new adult trees are seen in the wild, they do not set seed and only reproduce from the stumps.

A conservation plan has been proposed that includes cultivation of seedlings, disease-free clone production from tissue culture, and continued aggressive conservation of Torreya taxilfolia in its native range. To that end, more work is needed to survey the full biodiversity of its habitat and learn what we can from studying the communities of flora, fauna and fungi that share the ecosystem of this, the rarest North American conifer.

Laurel Wilt Conference

CONFERENCE ON LAUREL WILT DISEASE AND NATURAL ECOSYSTEMS: IMPACTS, MITIGATION AND THE FUTURE

It is my pleasure to invite you to attend this national conference addressing laurel wilt disease, to be held in Coral Springs, Florida, June 16-18, 2015.

Laurel wilt is one of the most damaging invasive exotic tree diseases to affect forests in North America. Current estimates show that hundreds of millions of trees have died, with multiple significant radiating effects on ecosystem structure and function, endangered species and cultural impacts. The disease continues to expand into new areas affecting diverse resources (sassafras in Louisiana and the swamp bay tree islands of the Everglades, for example).

A concerted effort between the research community, agencies, and land and natural resource managers is needed to address this rapidly expanding threat.

This conference provides a timely opportunity to learn the most recent state of knowledge regarding laurel wilt, its biology, impacts in native ecosystems and efforts to mitigate for its devastating effects.

We encourage individuals from across the country to join us and be a part of this important national discussion.

 

For more information visit http://conference.ifas.ufl.edu/LaurelWilt/