Invasive shot-hole borer, Euwallacea sp. nr. fornicatus
Native to: Southeast Asia (likely)
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Species Description: The invasive shot-hole borer, or ISHB, is an ambrosia beetle, which means that it has a special, symbiotic relationships with one or more species of fungi. When ISHB bores its long, winding galleries (tunnels) into a host tree, it allows the fungi to infect the tissue of that host. One of ISHB's associated fungi, Fusarium euwallaceae, causes a tree disease called Fusarium Dieback. This disease prevents host trees from taking up water and nutrients properly, leading to the death of the branches and sometimes the entire tree.
Impact in California: ISHB was first detected in Los Angeles in 2010 and has attacked over 260 tree species so far, including native plants, urban trees, and agricultural crops like avocado. It spreads the Fusarium Dieback disease among all of these susceptible host plants, and has been linked to the deaths of hundreds of thousands of trees in Southern California.
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What We Can Do: Scientists are researching the biology of the beetle, the disease, and host response to treatments in an attempt to better understand and manage this destructive species. We developed this model in order to illustrate the likelihood that ISHB would occur in a given area, based on the vulnerability of the environment. The model is informed by field observations that were collected by researchers from 2012 to 2016. Learn more about invasive shot-hole borer at www.pshb.org.
A female invasive shot-hole borer is about the size of a sesame seed.
(Photo: Monica Dimson)
Data source:
Species records provided by UC Cooperative Extension - Orange County; the Eskalen Lab at UC Riverside; and USDA Forest Service, Forest Health Protection Service.
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Acknowledgements:
We would like to thank John Kabashima, Tom Coleman, Akif Eskalen, and Shannon C. Lynch for sharing ISHB field data.