Team of scientists tackle shot hole borer at UC Irvine

When trees at UC Irvine became infested with polyphagous shot hole borer, the university assembled a team of scientists to use the campus as a living laboratory to study ways to protect trees from the pest, reported Sanden Totten on KPCC, the public radio station in Southern California.

Two members of the team are UC Agriculture and Natural Resources experts: Akif Eskalen, UC ANR Cooperative Extension specialist in the Department of Plant Pathology at UC Riverside, and John Kabashima, UC ANR farm advisor emeritus.

PSHB, a native of Asia, is killing hundreds of trees at UCI and thousands of trees in Orange, Los Angeles, and San Diego counties, including ornamental trees in urban landscapes, avocado and other farm trees in agricultural areas, and native tree species on wildland. 

"The value of trees killed by PSHB will be in the millions of dollars," Kabashima said.

The pest damages trees by boring into the bark and carrying a fungus inside.

"They actually farm that fungus as a food source," Eskalen said.

The fungus clogs the water-conducting tissue inside the tree, leading to the tree's death.

The scientists are battling the pest on many fronts, injecting various insecticide and fungicide combinations to kill the pest and fungus, and even limiting water to some trees to see if dry conditions will have an impact on the pest and fungus. However, the scientists acknowledge the complexity of the problem.

"When we do a test on sycamores that does not necessarily translate to what's going to happen when we treat an oak," Kabashima said.

For that reason, Eskalen says it's unlikely researchers will be able to eradicate the pest.

"At the end, we're going to have to learn to live with it," he said.

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