An invasive beetle species has been discovered in San Jose that has destroyed tens of thousands of healthy trees throughout Southern California, posing a threat to over 65 tree species in the region.
The shot borer digs tunnels into trees and introduces a fungus that serves as food for the beetles and prevents the trees from transporting water and nutrients, often killing them in the process, the Santa Clara County Agriculture Department said Friday.
The beetle is native to Southeast Asia and was first discovered in Los Angeles in 2003. It is believed to have entered the area via packaging materials. Agricultural officials and arborists have been battling the epidemic for years in LA, Orange, Riverside, San Bernardino, San Diego, Santa Barbara and Ventura counties.
“It poses a significant threat to our urban forests,” says Rhonda Berry, executive director of Our City Forest, a San Jose-based nonprofit that has been advocating for urban forest development for 30 years.
It’s unclear when the beetle arrived in the Bay Area or how widespread the infestation is, officials said. The insects may have been in San Jose for several years.
It may be too late to eradicate the species in San Jose. Researchers are trying to determine the extent of the infestation.
“We are asking the public for help in identifying trees that are infested with invasive shot borers. This will help us determine the extent of the infestation,” said Drew Raymond, acting agriculture commissioner for Santa Clara County. “We probably can’t get rid of the invasive shot borer at this point, but we can contain the infestation to protect as many of our trees as possible.”
The beetle is no larger than a sesame seed and is a particular nuisance because it can kill several tree species, including the ash-leaved maple, the California plane tree, the California white oak, the Japanese maple and the American sweetgum.
To identify an infestation, look for trees with dead or dying upper branches or wet patches that may look like a dark discharge from the tree’s bark. Other signs include small entry and exit holes in trees that are perfectly round and about the size of the tip of a ballpoint pen, surrounded by drilling dust and sugary deposits.
Anyone who sees such signs on their trees is asked to contact the Department of Agriculture at [email protected] or 408-918-4610. Department biologists can help determine if the invasive insect is present.
Berry urged community members to be proactive in monitoring their trees, pointing out that 85% of urban forests are maintained by private individuals rather than public entities.
“The only way to stop the destruction of the urban forest is for citizens to check their trees,” she said.
