''Agrilus auroguttatus '' is a species of

jewel beetle Buprestidae is a family of beetles known as jewel beetles or metallic wood-boring beetles because of their glossy iridescent colors. Larvae of this family are known as flatheaded borers. The family is among the largest of the beetles, with some ...

in the United States, known by the common name goldspotted oak borer. It is a woodboring beetle best known for destroying stands of oak trees in the

Cleveland National Forest Cleveland National Forest encompasses 460,000 acres (), mostly of chaparral, with a few riparian areas. A warm dry mediterranean climate prevails over the forest. It is the southernmost U.S. National Forest of California. It is administered by th ...

San Diego County, California San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the fi ...

, in the United States. It was originally considered a subspecies of the Central American species '' Agrilus coxalis'', and much of the literature refers to it by this name, but now it is regarded as a separate species, known only from Arizona and California.

Description

The adult gold spotted oak borer is dull dark metallic green in color with three characteristic yellow spots on each forewing. It is about a centimeter long. The larva is white and legless and reaches 18 millimeters in length. It is extremely difficult to distinguish from '' Agrilus coxalis'', a species known from Mexico and

Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...

History and impact

Significant oak mortality was noted in the area starting in 2002 near Descanso, California.Coleman, T. W
New insect evidence in continuing oak mortality
US Forest Service. August 4, 2008. It was thought that drought was causing the decline until surveys revealed evidence of damage to healthy trees. On investigation it was determined that the agent causing the damage was ''Agrilus auroguttatus'' (misidentified as ''A. coxalis''), a beetle not previously noted in the area. The tree species most affected are the coast live oak (''Quercus agrifolia'') and

California black oak ''Quercus kelloggii'', the California black oak, also known as Kellogg oak, is an oak in the red oak section (genus ''Quercus'', section ''Lobatae'', series ''Agrifoliae''), native to western North America. Although genetically separated from the ...

(''Quercus kelloggii''). The

canyon live oak ''Quercus chrysolepis'', commonly termed canyon live oak, canyon oak, golden cup oak or maul oak, is a North American species of evergreen oak that is found in Mexico and in the western United States, notably in the California Coast Ranges. This ...

(''Quercus chrysolepis'') and

silverleaf oak ''Quercus hypoleucoides'', the silverleaf oak or the whiteleaf oak is a North American species of oak tree or shrub. It grows in the southwestern United States and northern Mexico. Description ''Quercus hypoleucoides'', though usually seen as ...

(''Quercus hypoleucoides'') are also affected.New Pest Advisory Group
NPAG Report: ''Agrilus coxalis''
. January 22, 2009.USDA Forest Service
Pest Alert: New Pest in California
October 28, 2008 The insect was first seen in the region in 2004 at Cuyamaca Rancho State Park, and it was confirmed to be the cause of oak damage in 2008 when adults and larvae were collected from the host trees. Little is known about the life history of the insect, whether it is introduced or moving into the area as part of a natural range expansion, or its current distribution. Since dead oaks were first seen near Descanso, damage was found on 67% of oaks examined in surveys, and about 13% of the trees were dead. The affected region is an area 50 by 40 kilometers mostly within National Forest boundaries in the

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Coast Ranges, which ...

east of San Diego. Damage from the beetle takes the form of blackened larval feeding galleries revealed in the wood when woodpeckers remove bark, red and black staining on the bark that occurs when sap drains from damaged phloem, thinning grayish crowns on injured trees, and dead twigs and branches. The adult leaves D-shaped exit holes on the outside of the tree. Initially, it was estimated that 15,000 individual trees have been killed by this pest. On September 3, 2011, the

San Diego Union-Tribune ''The San Diego Union-Tribune'' is a metropolitan daily newspaper published in San Diego, California, that has run since 1868. Its name derives from a 1992 merger between the two major daily newspapers at the time, ''The San Diego Union'' and ...

published a correction of this estimate by UC Riverside researchers that puts the number at 80,000 trees killed. Dead trees increase the likelihood and severity of wildfire in this already highly fire-prone area. Current research is aimed toward locating a predator or

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

that preys on the beetle larvae, but will not have serious impact on other native species. Until further study yields suggestions for the management of this pest insect, the US Forest Service advises forestry workers to use containment guidelines now in practice for the control of similar jewel beetle pests, such as the emerald ash borer and

bronze birch borer ''Agrilus anxius'', the bronze birch borer, is a wood-boring buprestid beetle native to North America, more numerous in warmer parts of the continent and rare in the north. It is a serious pest on birch trees (''Betula''), frequently killing t ...

. If the beetle was introduced to the area, it may have come in on

firewood Firewood is any wooden material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form, compared to other forms of wood fuel like pellets or chips. Firewood can ...

. Scientists advise against transporting oak wood since it may spread the pest.Krier, R
Scientist leads study of oak-killing beetle
''

'' June 4, 2009.

References

External links

Gold spotted Oak Borer from the Center for Invasive Species ResearchGoldspotted Oak Borer website: www.GSOB.org
{{Authority control auroguttatus Woodboring beetles Natural history of San Diego County, California Beetles described in 1905