Sesame seed-size insect is victimizing trees in Southern California

The polyphagous shot hole borer is taking up residence in California trees from San Diego to Santa Monica and as far east as Riverside County, drilling circular tunnels and spreading fungal spores that kill trees from the inside out, reported Amina Kahn in the Los Angeles Times Science Blog.

Akif Eskalen, UC Cooperative Extension plant pathology specialist at UC Riverside, wants to contain this invasive bug before it spreads throughout Southern California.

"If we can't control them," Eskalen said, "they are going to wipe out all our trees."

Box elders, sycamores, American sweetgum, maple and coast live oaks are susceptible to polyphagous shot hole borer attack. In urban and suburban areas, the dead and dying trees can pose fire and limb falling dangers. In the agricultural sector, avocado trees could face huge financial losses. In the fight against the pest, the California Avocado Commission has provided Eskalen $800,000 to broaden his investigation into this mysterious species of ambrosia beetle. 

In March, Eskalen and his colleagues - UC Riverside entomologist Richard Stouthamer and Huntington Library curator of woody collections Tim Thibault - spent two weeks in Vietnam, where PSHB originates, searching forests and fields for natural enemies of the fungus spread by the pest. They collected a host of possible allies, whose DNA is now being analyzed in the lab.

"I am very hopeful that we are going to find some solutions to control this fungus," Eskalen said. "We have to."

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