|Freeman, S - Volcani Center (ARO)|
|Sharon, M - Volcani Center (ARO)|
|Maymon, M - Volcani Center (ARO)|
|Protasov, A - Volcani Center (ARO)|
|Margalit, O - Volcani Center (ARO)|
|Maoz, Y - Volcani Center (ARO)|
|Mendel, Z - Volcani Center (ARO)|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/18/2015
Publication Date: 9/18/2015
Citation: Freeman, S., Sharon, M., Maymon, M., Protasov, A., Margalit, O., Maoz, Y., O'Donnell, K., Mendel, Z. 2015. Association of the symbiotic fungi Fusarium euwallaceae, Graphium sp. and Acremonium sp., with the ambrosia beetle Euwallacea nr. fornicatus in avocado [abstract].
Technical Abstract: The ambrosia beetle, Euwallacea nr. fornicatus (Coleoptera:Scolytinae), is a new invasive species to Israel. To date, the beetle has been recorded from 48 tree species representing 25 plant families. Amongst the most affected are avocado, castor-bean and box elder. Isolations from beetle heads revealed that three fungal species are carried within the mandibular mycangia: Fusarium euwallaceae, Graphium sp. and Acremonium sp. Adult females excavate galleries in the xylem and inoculate them with the three associated fungi. All three fungi were isolated from galleries in different host species. Larvae and adult beetles feed on F. euwallaceae and Graphium sp. but not on Acremonium sp. and non-specific Fusarium spp. Isolations from beetle heads revealed that Graphium and Acremonium species are much more common in callow adults. Xylem in the vicinity of the gallery was stained brown, became necrotic and very likely non-functional, resulting in branch dieback. However, F. euwallaceae and probably the other two mycangial symbionts do not spread systemically in the host tissue. In some tree species, the beetle penetrated the sapwood with minimal or no fungal colonization, and therefore they did not reproduce. To date, the beetle has spread to approximately 60% of the avocado plantations in Israel. In 25% of the infested plantations, the damage level is ranked as moderate to severe. The same beetle and associated fungi were recently found in California as confirmed by molecular analyses. Interactions of Graphium sp. and Acremonium sp. with the beetle, and their putative pathogenic role in avocado dieback, are under investigation.