Euwallacea sp. IS/CA
(Sometimes known as Euwallacea nr. fornicatus Eichhoff and Xyleborus fronicatus Eichhoff).
Common name: Polyphagous shot hole borer.
Systematic position: Insecta, Holometabola, Coleoptera, Curculionidae.
Geographical distribution: California, Israel, and Vietnam.
Morphology: Body of female about 2.5 mm long, mostly black, thorax and elytra covered with small protuberances and stiff short hairs. Male smaller, with black thorax and brown elytra.
Host plants: About 50 and 200 species, in Israel and southern California, respectively, the most important being avocado.
Life history: The beetles live within galleries that they mine in host trees. They vector several fungi, of which Fusarium euwallaceae Freeman, Mendel, Aoki and O’Donnell, located in a cavity (mycacangia) in the female head, is the more important. The beetles arrive at the host trees, especially avocado, and mine galleries there. Large and medium diameter brances are relatively resistant to the pest, probably due to much sugar exudation there, whereas thin branches are more suitable. The fungus then infests and grows on the walls of borrows tunneled in the sapwood of the host trees. The larvae and adults feed on the fungus, raising a generation in 6-7 weeks at 25C. The pest disperses by flight.
Economic importance: The damage caused by this beetle is due to avocado branch wilting and to vectoring the fungus F. euwallaceae. The leaves of infested, and then infected, host trees (e.i. avocado) wilt, become discolored, the branches exude a typical gum and may break. Weakened young, and even mature trees may subsequently die. The gum exudation becomes evident as it is colonized by whitish fungi (“sugaring”). The beetle-fungus complex may endanger avocado plantations.
Management
Monitoring: The chemical quercivorol can be used for monitoring the pest, especially in spring, when the beetles disperse.
Horticultural methods: Both chipping and solarisation of infested logs reduced pest emergence and its boring activities.
Mass trapping: Quercivorol can be used for mass trapping the pest, especially in the spring.
Chemical control: A pyrethroid and imidacloprid controlled the pest in California.
References
Byers, J.A., Maoz, Y. and Levi-Zada, A. 2017. Attraction of the Euwallacea sp. near fornicatus (Coleoptera: Curculionidae) to quercivorol and to infestations in avocado. Journal of Economic Entomology 110: 1512-1517.
Carrillo, D., Narvaez, T., Cossé, A.A., Stouthamer, R. and Cooperband, M. 2015. Attraction of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae) to lures containing quercivorol. Florida Entomologist 98:780-782.
Freeman, S. (and 7 co-authors). 2012. Obligate feed requirement of Fusarium sp. nov., an avocado wilting agent, by the ambrosia beetle Euwallacea aff. fornicata. Symbiosis 58: 245-251.
Freeman, S. (and 7 co-authors). 2013. Fusarium euwallaceae sp. nov. – a symbiotic fungus of Euwallacea sp., an invasive ambrosia beetle in Israel and California. Mycologia 105: 1595-1606.
Freeman, S. (and 8 co-authors) 2016. Symbiotic association of three fungal species throughout the life cycle of the ambrosia beetle Euwallacea nr. fornicatus. Symbiosis 68: 115-128.
Jones, M.E. and Paine, T.D. 2015. Effect of chipping and solarization on emergence and boring activity of a recently introduced ambrosia beetle (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae) in Southern California. Journal of Economic Entomology 108: 1852-1859.
Jones, M.E. and Paine, T.D. 2017. Potential pesticides for control of a recently introduced ambrosia beetle (Euwallacea sp.) in southern California. Journal of Pest Science 106: 1–10.
Mendel, Z. (and 6 co-authors) 2017. The role of Euwallacea nr. fornicatus_ (Coleoptera: Scolytinae) in the wilt syndrome of avocado trees in Israel. Phytoparasitica 45: 341-349.