Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2013
Publication Date: 8/14/2013
Citation: Ploetz, R.C., Ploetz, J.N., Konkol, J.L., Carrillo, D., O'Donnell, K., Campbell, A., Duncan, R.E. 2013. Fusarium symbionts of an ambrosia beetle (Euwallacea sp.) in southern Florida are pathogens of avocado, Persea americana [abstract]. American Phytopathological Society. Interpretive Summary:
Technical Abstract: Fusarium dieback, a destructive disease of avocado (Persea americana), was reported in California and Israel in 2012. It is associated with an ambrosia beetle, Euwallacea sp., and damage caused by an unnamed symbiont of the beetle in Clade 3 of the Fusarium solani species complex (FSSC) designated phylogenetic species AF-2. In 2012, a beetle that resembled Euwallacea fornicatus morphologically was recovered in southern Florida from infested avocado trees, and Lindgren funnel and Tanglefoot traps. Adult female beetles were assayed for fungi by macerating and dilution plating different body parts on half-strength PDA+streptomycin sulfate. A novel phylogenetic species within the FSSC designated AF-8 predominated in heads but was almost completely absent in the rest of the body (thoraxes+abdomens). When heads were surface disinfested prior to assay, AF-8 was often the only fungus isolated from the insect. Thus, it is presumed that AF-8 is a symbiont of the beetle that resides in its mandibular mycangia. AF-8 was recovered from 23 of 33 individuals, often to the exclusion of other fungi (20 of 23 individuals). Colony forming units (CFUs) of AF-8 ranged from 0 to 8600 per individual, and significantly more CFUs were isolated from living vs. dead beetles. Isolates of AF-8, and two other FSSC species that associated less frequently with the beetle, caused slowly developing lesions in avocado sapwood in greenhouse and field experiments.