The goldspotted oak borer (Agrilus auroguttatus Schaeffer) is an invasive, wood-boring jewel beetle from southern Arizona that has caused considerable damage to native oak species in southern California. However, scientists have been unsure about how it spread from Arizona to California — was it accidentally transported by humans, or did it get there on its own?
To find out, researchers at the University of California, Riverside tethered oak borers to computerized flight mills in order to assess their flight capabilities, and to determine potential future environmental and economic risks they might cause.
The scientists were able to collect information on total distances flown, flight times and velocities, number and duration of flight bouts, and postflight weight. Their research — the first information on the dispersal potential of this invasive beetle — was recently published in the Journal of Economic Entomology.
The scientists found that the insects’ nutritional status, body size, and age had significant influences on overall flight performance, but nutritional status was probably the most important.
“Age had a significant effect on flight performance when adults were starved, but not when adults were fed,” they wrote.
This led them to conclude that the oak borer probably did not make it to California on its own because because they would have lacked possible food sources while crossing the Sonoran and Mojave deserts.
“Overall, results of these flight mill assays indicate that A. auroguttatus is unable to disperse long distances across habitats that lack suitable oak hosts,” they wrote. “This work supports the hypothesis that human-aided transportation via infested oak firewood from southern Arizona across the Sonoran desert likely caused the initial introduction, and subsequent satellite infestations, of A. auroguttatus within southern California’s native oak woodlands.”
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