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United States Department of Agriculture

Agricultural Research Service

Research Project: PROTECTION OF SUBTROPICAL AND TROPICAL AGRICULTURE COMMODITIES AND ORNAMENTALS FROM EXOTIC INSECTS

Location: Subtropical Horticulture Research

Title: Laurel wilt: An unusual and destructive disease of American members of the Lauraceae

Authors
item Ploetz, R -
item Smith, J -
item Hughes, M -
item Inch, S -
item Dreaden, T -
item Spence, D -
item Carrillo, D -
item Duncan, R -
item Pena, J -
item Kendra, Paul
item Sandaran, S -
item Ehsani, R -
item Held, B -
item Blanchette, R -
item Campbell, A -
item White, T -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 20, 2012
Publication Date: August 12, 2012
Repository URL: http://Ambrosia Beetle/Fungal Symbiont Workshop; UC Riverside Center for Invasive Species Research; Riverside, CA; 12-14 Aug 2012
Citation: Ploetz, R., Smith, J., Hughes, M., Inch, S., Dreaden, T., Spence, D., Carrillo, D., Duncan, R., Pena, J., Kendra, P.E., Sandaran, S., Ehsani, R., Held, B., Blanchette, R., Campbell, A., White, T. 2012. Laurel wilt: An unusual and destructive disease of American members of the Lauraceae. Meeting Abstract. Ambrosia Beetle/Fungal Symbiont Workshop.

Interpretive Summary: Laurel wilt kills American members of the Lauraceae plant family (Laurales, Magnoliid complex). These include significant components of Coastal Plain forest communities in the SE USA, most importantly redbay (Persea borbonia), as well as the commercial crop avocado (P. americana). Laurel wilt is caused by the ascomycete Raffaelea lauricola (Ophiostomatales), which has an Asian ambrosia beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), as a vector. In May 2002, X. glabratus was reported for the first time in the Western Hemisphere in Port Wentworth, GA. Laurel wilt is now widely spread in the SE USA due to its mobile insect vector, the movement of infested wood, and the presence of native and non-native plants that are susceptible to the disease and on which the vector reproduces. Diverse strategies have been examined for managing laurel wilt, including host resistance (avocado and redbay), the use of fungicides (avocado and redbay), and insecticides and repellents (avocado). To date, no highly efficacious and cost-effective measure has been identified. In the absence of such a measure cultural methods, in particular the prompt identification, removal and destruction of infected/infested trees (sanitation), will play significant roles in disease mitigation. Ongoing work investigates a remote sensing method to rapidly identify affected trees. In artificially inoculated avocado, plant size was positively correlated with disease severity. Since significant symptoms develop internally in the sapwood before external symptoms are evident, management of the disease with fungicides or other means will be difficult if measures are delayed until after external symptoms develop. Despite its rapid acropetal and basipetal movement in host xylem, R. lauricola is scarcely evident in affected plants. Microscopic localization of the fungus and its detection via DNA analyses is inconsistent, especially in avocado. Vascular function and hydraulic conductivity is dramatically reduced in affected avocado. The pathogen has been recovered from nine species of scolytines that have been recovered from laurel wilt-affected avocado, redbay and swampbay. Compared to X. glabratus, fewer propagules of R. lauricola have been detected in other beetle species (100s or 10s vs 1,000s). However, the rarity of X. glabratus in laurel wilt-affected avocado (no or very few individuals of this species are recovered from this host) and what appear to be sufficient levels of inoculum in several of the other species to cause disease raised the possibility that X. glabratus is not the only vector of this pathogen. Recently, this possibility was confirmed on avocado and redbay. Other means by which the pathogen could be transmitted include movement via root grafts (probable), pruning equipment (less likely), and avocado fruit, seed and scion material (doubtful).

Technical Abstract: Laurel wilt kills American members of the Lauraceae plant family (Laurales, Magnoliid complex). These include significant components of Coastal Plain forest communities in the SE USA, most importantly redbay (Persea borbonia), as well as the commercial crop avocado (P. americana). Laurel wilt is caused by the ascomycete Raffaelea lauricola (Ophiostomatales), which has an Asian ambrosia beetle, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), as a vector. In May 2002, X. glabratus was reported for the first time in the Western Hemisphere in Port Wentworth, GA. Laurel wilt is now widely spread in the SE USA due to its mobile insect vector, the movement of infested wood, and the presence of native and non-native plants that are susceptible to the disease and on which the vector reproduces. Diverse strategies have been examined for managing laurel wilt, including host resistance (avocado and redbay), the use of fungicides (avocado and redbay), and insecticides and repellents (avocado). To date, no highly efficacious and cost-effective measure has been identified. In the absence of such a measure cultural methods, in particular the prompt identification, removal and destruction of infected/infested trees (sanitation), will play significant roles in disease mitigation. Ongoing work investigates a remote sensing method to rapidly identify affected trees. In artificially inoculated avocado, plant size was positively correlated with disease severity. Since significant symptoms develop internally in the sapwood before external symptoms are evident, management of the disease with fungicides or other means will be difficult if measures are delayed until after external symptoms develop. Despite its rapid acropetal and basipetal movement in host xylem, R. lauricola is scarcely evident in affected plants. Microscopic localization of the fungus and its detection via DNA analyses is inconsistent, especially in avocado. Vascular function and hydraulic conductivity is dramatically reduced in affected avocado. The pathogen has been recovered from nine species of scolytines that have been recovered from laurel wilt-affected avocado, redbay and swampbay. Compared to X. glabratus, fewer propagules of R. lauricola have been detected in other beetle species (100s or 10s vs 1,000s). However, the rarity of X. glabratus in laurel wilt-affected avocado (no or very few individuals of this species are recovered from this host) and what appear to be sufficient levels of inoculum in several of the other species to cause disease raised the possibility that X. glabratus is not the only vector of this pathogen. Recently, this possibility was confirmed on avocado and redbay. Other means by which the pathogen could be transmitted include movement via root grafts (probable), pruning equipment (less likely), and avocado fruit, seed and scion material (doubtful).

Last Modified: 9/10/2014
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