|CARRILLO, D - University Of Florida|
|AVERY, P - University Of Florida|
|NAVARRETE, J - University Of Florida|
|DUNCAN, R - University Of Florida|
|CAVE, R - University Of Florida|
|CRANE, J - University Of Florida|
|Rooney, Alejandro - Alex|
|PENA, J - University Of Florida|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2014
Publication Date: 11/1/2014
Publication URL: http://handle.nal.usda.gov/10113/60615
Citation: Carrillo, D., Dunlap, C.A., Avery, P.B., Navarrete, J., Duncan, R.E., Jackson, M.A., Behle, R.W., Cave, R., Crane, J., Rooney, A.P., Pena, J.E. 2014. Entomopathogenic fungi as a biological control for the vector of the laurel wilt disease: The redbay ambrosia beetle. Biological Control. 81:44-50.
Interpretive Summary: The red bay ambrosia beetle (RAB) is an invasive pest species that threatens both natural ecosystems in the Southern United States and the Florida avocado industry, which accounts for approximately 12-14% of avocado production in the United States annually. This species attacks trees of the laurel family especially redbay and swampbay trees, which are important parts of natural ecosystems across the United States, and avocado trees, which is a $54 billion per year industry in Florida. Only a few chemicals are registered for used against this pest. Thus, current control strategies mostly involve cultural/mechanical practices, centering on the removal of infested trees. Our research has identified a new pest control option to combat the RAB threat. Three insect-killing fungi were shown to be able to kill the RAB at significant levels. Of these three species, however, the fungus Beauveria bassiana showed the fastest response; interestingly, this species is available commercially and can therefore be used immediately to combat the RAB. These findings provide a new weapon that avocado growers and managers of natural redbay/swampbay ecosystems can use to control infestations of the RAB.
Technical Abstract: The redbay ambrosia beetle (RAB), Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae) vectors the fungal pathogen, Raffaelea lauricola, which causes laurel wilt (LW), a lethal disease of trees in the family Lauraceae, including the most commercially important crop in this family, avocado, Persea americana. The objective of this study was to determine the susceptibility of RAB to infection and subsequent death by exposure to four commercial strains of entomopathogenic fungi. RAB females were exposed separately to two strains of Isaria fumosorosea (Ifr 3581) and PFR 97® 20% WDG (PFR), one strain of Metarhizium brunneun (Met F52® ES), and one strain of Beauveria bassiana (BotaniGard® ES). RAB females were dipped in fungal spore solutions and their lethal times (LT50) determined. Contact with any of the biopesticides resulted in death of all RAB females within a few days. LT50s of RAB females exposed to the different entomopathogenic fungi ranged from 2.92 days (B. bassiana) to 4.75 days (I. fumosorosea PFR). B. bassiana and M. brunneum killed RAB females faster, followed by I. fumosorosea Ifr and PFR. RAB females dipped in B. bassiana and M. brunneum fungal suspensions had the highest number of viable spores attached to their bodies, followed by I. fumosorosea (Ifr). Beetles dipped in I. fumosorosea (PFR) suspension had significantly less viable spores attached to their bodies. No significant differences were observed in the mortality of beetles that were dipped in fungal spore solutions and then offered avocado logs as substrate, compared to beetles that were allowed to walk on logs previously treated with the different fungi. Beetles were able to bore into the logs and construct galleries but they were found dead inside the galleries few days after exposure to the entomopathogens. Entomopathogenic fungi infection in dead beetles was confirmed through molecular techniques. This is the first study to demonstrate that entomopathogenic fungi are potential biological control agents against adult RAB. Additional research to determine the effectiveness of entomopathogenic fungi under field conditions to control RAB infestations is granted.