A new threat to California oaks: Goldspotted oak borer
There are few plants as emblematic of the California natural landscape as the native oak. Unfortunately, these majestic trees are threatened again, this time by an invasive beetle.
The goldspotted oak borer (GSOB), Agrilus coxalis, already has killed 20,000 native oaks in San Diego County and is likely to spread northward. Almost 90% of susceptible oaks in some areas are infested and dead or dying.
UC IPM Extension Entomologist Mary Louise Flint has joined U.S. Forest Service entomologists Steve Seybold and Tom Coleman in a cooperative effort to study the biology and ecology of the pest and develop an integrated strategy to contain it.
The research program includes developing better traps and lures to detect the pest and map its spread and providing tools for timing management programs in the future. Although related to the emerald ash borer that has invaded the Eastern United States, GSOB does not respond to the commercial lures available for that pest.
GSOB has only one generation a year, and data from current studies suggest that adults begin to emerge in May with peak emergence in late June to early July.
GSOB is likely spread to new areas as people move infested logs and firewood. A primary goal of the team’s project is to evaluate ways to treat infested wood when it is harvested and before it is moved. Preliminary results indicate that chipping is very effective. Further trials of chipping and solarization are underway.
In another project, UC Riverside Entomologist Mark Hoddle is investigating the potential for biological control of the pest.
To help forest managers and land owners identify and track the pest in their areas, UC IPM recently released an illustrated field identification guide. Find it in the Exotic and Invasive Pests section of the UC IPM Web site.
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