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United States Department of Agriculture

Agricultural Research Service


Location: Bacterial Foodborne Pathogens & Mycology Research Unit

Title: The invasive ambrosia beetle Euwallacea fornicates vectors an exotic symbiotic Fusarium species that threatens avocado production in Israel

item Freeman, S -
item Sharon, M -
item Okon-Levy, -
item Protasov, A -
item Eliyhu, M -
item Noi, M -
item Rabaglia, R -
item O Donnell, Kerry
item Mendel, Z -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 28, 2012
Publication Date: N/A

Technical Abstract: The invasive ambrosia beetle (Euwallacea fornicatus Eichhoff) was first recorded in Israel in 2009, and it has been shown to vector an exotic fusarial pathogen. Multilocus molecular phylogenetic analyses indicate that the pathogen represents a novel symbiotic Fusarium sp. within Clade 3 of the Fusarium solani species complex. Adult beetles and their larva feed on the fungal mycelium which is inoculated into galleries by adult females tunneling in the xylem. The beetle is known to attack over 100 tree species worldwide. In Israel it develops successfully on avocado (Persea americana), box elder (Acer negundo) and castor oil plant (Ricinus communis), leading to severe injury and tree mortality. While there is no visible injury to the cortex, xylem under the area bored by the beetle is stained brown by the fungus and becomes necrotic. Typical symptoms in avocado include discoloration of the outer bark surrounding the penetration spot, which is covered by a white powdery exudate termed 'persitol'. Koch postulate tests were performed successfully with the symbiotic Fusarium sp. on detached branches, on trees inoculated within a greenhouse, and on mature trees in an avocado orchard. The beetle attacks the major avocado cultivars in Israel, with Hass and Pinkerton appearing to be the most susceptible. Infected trees display: (i) wilting of branches and discoloration of leaves; (ii) wilting and collapse of branches laden with yield; and (iii) mortality of trees. The beetle-fungus complex has become a serious threat to the future of the avocado industry in Israel.

Last Modified: 4/24/2014
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