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Non-Native Beetle Destroying Oaks in Southern California

A beetle first detected in California in 2004 has now attacked 67 percent of the oak trees in an area 30 miles east of San Diego, according to a recent report. The beetle is Agrilus coxalis and the reporting researchers have proposed that it be given the common name: goldspotted oak borer. Land managers and scientists are concerned about further spread of the beetle infestation because oaks are the dominant tree species in the area. Further tree mortality will increase fire danger and decrease wildlife habitat in southern California. The managers and scientists are also concerned that drought and climate change will make more oaks susceptible to this insect that is not native to California. Oak trees have a nearly continuous distribution in the state, reaching from the infestation area north to the Oregon border. “We don't know how the beetle arrived in San Diego County because there's a broad barrier of desert around the localities where it was previously collected in Arizona, Guatemala, and Mexico," said one of the study's authors. "We suspect it was either recently brought to California or somehow expanded its range." There are reports of oak firewood from Mexico frequently being brought into the area in the past 20 years and that could be how it was introduced, the scientist said. Further research is necessary to determine how to halt the spread of the beetle infestation. [Press release]