Update on invasive shot hole borers: Online training now available

By Sabrina Drill, Natural Resources Advisor, UCCE Ventura

Invasive shot hole borers (ISHB) are a pest and disease complex potentially affecting over 200 tree species, but posing a strong risk to box elders, sycamores, and other riparian and urban trees, as well as being a nuisance pest for avocado. The beetles have also been shown to attack a wide variety of common and less common ornamental species. For a complete host list, visit https://ucanr.edu/sites/pshb/overview/SHB_Reproductive_Hosts/. The tiny beetles burrow into the trunks and branches of trees and create galleries where they cultivate a fungus that utilizes the trees own circulatory system, harming and in some cases killing the tree. We know the beetle can reproduce in over 60 species of trees, and they have devasted natural riparian areas, though we are beginning to see recovery of some infestations. Currently, the most effective management method is to remove infested wood, sometimes entire trees, and chip what is removed to minus 1”.

ISHB are now firmly established in Ventura County, with finds throughout the Santa Clara River Valley in traps from South Mountain to Toland Park in Santa Paula, and several infested box elder and sycamores in Meiner's Oaks and Ojai. It appears not to have crossed into the county in the south, but there are still active infestations in western Los Angeles County.

Personnel from UC ANR, CDFA, the Ventura County Agricultural Commissioner, and the US Forest Service have taken lead roles in developing a statewide ISHB action plan for the California Invasive Species Advisory Committee, with an initial investment of $5 million to work on controlling the pest. Plan elements include research in the ecology and control of the pest, including work to develop biocontrol; an early detection and surveillance program; addressing green waste and other pathways of spread, and outreach and education.

In terms of education and outreach, an area where Cooperative Extension in Ventura, LA, Orange, and San Diego counties have led, we're excited to announce the release of a new on-line training course. Available through our website, https://ucanr.edu/sites/pshb/, the course is actually served by the eXtension on-line learning platform (and users will need to create a free account). The course consists of 4 chapters including history and impacts, biology, symptoms and look-alike pests, and monitoring and management. While it can't fully replace a field training, it can be a good way to familiarize new staff to the issues.