Recovery plan for laurel wilt on redbay and other forest species caused by Raffaelea lauricola and disseminated by Xyleborus glabratus

Authors: HUGHES, M - University Of Florida; SMITH, J - University Of Florida; PLOETZ, R - University Of Florida; HULCR, J - University Of Florida; CARRILLO, D - University Of Florida; STELINSKI, L - University Of Florida; MAYFIELD, A - Forest Service (FS); HANULA, J - Forest Service (FS); RABAGLIA, B - Forest Service (FS); Kendra, Paul; EICKWORT, J - Florida Department Of Agriculture; CAMERON, S - Forestry Commission; RIGGINS, J - Mississippi State University; PERNAS, T - National Park Service

Submitted to: Office of Pest Management National Plant Disease Recovery System
Publication Type: Government Publication
Publication Acceptance Date: 1/20/2015
Publication Date: 1/30/2015
Publication URL: http://www.ars.usda.gov/News/docs.htm?docid=14271
Citation: Hughes, M., Smith, J., Ploetz, R., Hulcr, J., Carrillo, D., Stelinski, L., Mayfield, A., Hanula, J., Rabaglia, B., Kendra, P.E., Eickwort, J., Cameron, S., Riggins, J., Pernas, T. 2015. Recovery plan for laurel wilt on redbay and other forest species caused by Raffaelea lauricola and disseminated by Xyleborus glabratus. Office of Pest Management Policy National Plant Disease Recovery System. http://www.ars.usda.gov/News/docs.htm?docid=14271.

Interpretive Summary: Laurel wilt is a highly destructive disease of the plant family Lauraceae within the United States. The insect vector, the redbay ambrosia beetle (RAB) (Xyleborus glabratus) was first detected in early monitoring and detection traps at Port Wentworth GA in 2002 and the unprecedented mortality of redbay (Persea borbonia) trees was reported in 2003. The disease (later named laurel wilt) is caused when the RAB introduces its pathogenic fungal symbiont (Raffaelea lauricola) into the sapwood of susceptible host trees during its boring activities. The fungus is housed within specialized pouches in the beetle’s mouthparts (mandibular mycangia), where it lives in a budding, yeast-like state. Once introduced into the xylem, host trees will react to the fungal invasion by the production of gums and tyloses, blocking water transport and causing wilt of the crown. Upon dissection of infected wood, xylem discoloration and evidence of ambrosia beetle attack (small holes and boring dust) is readily evident. The disease has now spread to over 115 counties in 6 states (FL, GA, AL, SC, NC, MS), causing significant mortality among redbay populations. Redbays serve an important ecological role in their respective forests and available studies show that losses of this species have had significant effects on forest composition and trophic structure. Several other forest lauraceous hosts (sassafras, pondspice [state endangered] and pondberry [federally endangered]) are susceptible to laurel wilt and have been affected by the disease in varying degrees. In addition, agricultural and ornamental non-native members of the Lauraceae within the United States are susceptible, indicating that laurel wilt is more than a disease of native forests. Complete eradication of the vector and pathogen is unfeasible due to the ability of the vector to persist in small diameter stems and the supposed ability of a single female to create new infectious populations. Currently, management options within a natural forest setting are limited and letting the disease run its course may be the only cost effective option, however, the following strategies may help reduce the impact of laurel wilt in forests and urban settings: - Continue to monitor the spread of the disease in order to assess the rate of movement and its impact upon the ecosystem - Minimize the human aided transport of firewood and unprocessed wood materials, a mechanism for long distance movement of the disease - Utilize chemical management options (fungicides and possibly insecticides) for the protection of high value trees - Continue the development of resistant host plant cultivars for restoration into the landscape - Collect and maintain germplasm for vulnerable hosts, especially rare species that may be in danger of extinction - Conduct research on disease biology, vector relations, management options, and host-parasite interactions - Continue to educate the public about laurel wilt, its economic and ecological effects and ways to garner public support and funding for continued management efforts

Technical Abstract: Laurel wilt is a highly destructive disease of the plant family Lauraceae within the United States. The insect vector, the redbay ambrosia beetle (RAB) (Xyleborus glabratus) was first detected in early monitoring and detection traps at Port Wentworth GA in 2002 and the unprecedented mortality of redbay (Persea borbonia) trees was reported in 2003. The disease (later named laurel wilt) is caused when the RAB introduces its pathogenic fungal symbiont (Raffaelea lauricola) into the sapwood of susceptible host trees during its boring activities. The fungus is housed within specialized pouches in the beetle’s mouthparts (mandibular mycangia), where it lives in a budding, yeast-like state. Once introduced into the xylem, host trees will react to the fungal invasion by the production of gums and tyloses, blocking water transport and causing wilt of the crown. Upon dissection of infected wood, xylem discoloration and evidence of ambrosia beetle attack (small holes and boring dust) is readily evident. The disease has now spread to over 115 counties in 6 states (FL, GA, AL, SC, NC, MS), causing significant mortality among redbay populations. Redbays serve an important ecological role in their respective forests and available studies show that losses of this species have had significant effects on forest composition and trophic structure. Several other forest lauraceous hosts (sassafras, pondspice [state endangered] and pondberry [federally endangered]) are susceptible to laurel wilt and have been affected by the disease in varying degrees. In addition, agricultural and ornamental non-native members of the Lauraceae within the United States are susceptible, indicating that laurel wilt is more than a disease of native forests. Complete eradication of the vector and pathogen is unfeasible due to the ability of the vector to persist in small diameter stems and the supposed ability of a single female to create new infectious populations. Currently, management options within a natural forest setting are limited and letting the disease run its course may be the only cost effective option, however, the following strategies may help reduce the impact of laurel wilt in forests and urban settings: - Continue to monitor the spread of the disease in order to assess the rate of movement and its impact upon the ecosystem - Minimize the human aided transport of firewood and unprocessed wood materials, a mechanism for long distance movement of the disease - Utilize chemical management options (fungicides and possibly insecticides) for the protection of high value trees - Continue the development of resistant host plant cultivars for restoration into the landscape - Collect and maintain germplasm for vulnerable hosts, especially rare species that may be in danger of extinction - Conduct research on disease biology, vector relations, management options, and host-parasite interactions - Continue to educate the public about laurel wilt, its economic and ecological effects and ways to garner public support and funding for continued management efforts