About the Beetles
A closely related beetle called the Kuroshio Shot Hole Borer (KSHB) has been detected in San Diego County. KSHB looks identical to PSHB and also carries disease-causing fungi, but the species are genetically distinct.1
Source: Gevorik Arakelian, L.A. County Department of Agriculture
Origin and History
Experts believe the beetles were introduced into southern California via products and/or shipping material from southeast Asia. These beetle species have been identified in Taiwan, Vietnam and China; however, the specific origin is unclear. The PSHB/FD complex is found in other locations including avocado trees in Israel.
PSHB/FD was first found at Whittier Narrows in Los Angeles County in 2003. From 2003-2010 the beetle was found on a few ornamental trees, then in 2010 it was the presumptive cause of the death of a large number of box elder street trees in Long Beach. In 2012 the beetle was collected from a backyard avocado tree in South Gate, and from several tree species at local botanical gardens. It now appears to be established in Los Angeles, Orange, and Riverside Counties. A single beetle was caught in Santa Cruz County in 2014.
KSHB/FD was confirmed to be attacking avocado trees in several commercial groves in north San Diego County in 2014 as well as several species of landscape trees in a single area in east San Diego County. In 2015, a large-scale infestation was identified in the southwestern area of the County at a public regional park.
1 Dimson, M., Kabashima, J., Eskalen, A. (2015). Polyphagous Shot Hole Borer + Fusarium Dieback: Identifying Symptoms and Look-Alike Pests. [Brochure]. n.c.: University of California Agriculture and Natural Resources.