About GSOB
The Goldspotted oak borer (GSOB) is an invasive beetle that was first detected in 2004 in San Diego County by the California Department of Food and Agriculture during a survey for exotic wood borers.
What is an invasive species?
Invasive species, alien species, or exotic pests, are non-native animals, microbes, diseases, or plants that threaten native species and the overall biodiversity. Non-native species become invasive when after getting to a new place by the intentions of humans, either directly or indirectly, are able to invade and outcompete local species. The resulting uncontrolled population growth and spread causes economic or environmental problems, such as the extinction of local animals or plants and the drastic modification of native ecosystems. As an invasive species, the GSOB is playing a major role in on-going oak mortality in southern California, permanently altering landscape ecosystems and their biodiversity.
What are the primary host species?
The three primary host species are Coast live oak, Canyon live oak, and the California black oak. They cover 39 million acres in California and it is possible that other oaks overlapping the ranges of these species may become hosts also. For example, the Engelmann oak has recently been attacked too, even if in low numbers.
What is an invasive species?
Invasive species, alien species, or exotic pests, are non-native animals, microbes, diseases, or plants that threaten native species and the overall biodiversity. Non-native species become invasive when after getting to a new place by the intentions of humans, either directly or indirectly, are able to invade and outcompete local species. The resulting uncontrolled population growth and spread causes economic or environmental problems, such as the extinction of local animals or plants and the drastic modification of native ecosystems. As an invasive species, the GSOB is playing a major role in on-going oak mortality in southern California, permanently altering landscape ecosystems and their biodiversity.
What are the primary host species?
The three primary host species are Coast live oak, Canyon live oak, and the California black oak. They cover 39 million acres in California and it is possible that other oaks overlapping the ranges of these species may become hosts also. For example, the Engelmann oak has recently been attacked too, even if in low numbers.
Coast live oakCoast live oak is an evergreen species with cupped leaves. Its acorns are slender and sharply pointed.
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Canyon live oakCanyon live oak is an evergreen species. The underside of older leaves appear gray, while newer leaves have fine red hairs.
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California black oakCalifornia black oak is a deciduous species that is found at higher elevation, 5,000-7,000 feet in southern California.
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How does the GSOB look like? Adult GSOBs are about 10 mm long and 2 mm wide and can be identified by the six golden-yellow spots on the dark green forewings. Adults cause minor and barely noticeable feeding damage to oak foliage, which does not impact tree health. Mature larvae are about 18 mm long and 3 mm wide, legless, white with a long slender appearance. Larvae feed under the bark primarily at the interface of the sapwood and phloem on the main stem and larger branches, resulting in limb and branch die back and eventually, tree death. |
Trees stressed by unfavorable conditions such as drought, disease, defoliation, high stand density, or poor tree care are most susceptible of the invasive beetle's attacks. Infested trees die after several years of injury inflicted by multiple generations of the beetle.
How can GSOB infestation be detected?
Oak trees display external symptoms of GSOB infestation that include premature twig dieback and crown thinning that worsens progressively over several years; presence of D-shaped emergence holes used by adults for emerging through the outer bark after they have completed pupation; black, wet staining or dark red bleeding on the bark, caused by larval feeding ; woodpecker damage caused by the removal of bark in search of larvae and pupae.
For more information about symptoms of infestation click here.
Each year, timber losses in California forests due to bark beetle attack exceed those caused by wild land fire. The existing and future oak mortality will impact ecosystems for years to come in addition to the large increase in hazardous trees that threaten life and property.
GSOB-killed oaks have only been found in San Diego County to date, however, it is expected that the area of infestation will continue to extend north beyond the county line and tree mortality will continue to increase due to adult flight from infested trees and because of new infestations initiated through beetles emerging from transported firewood.
Resources
For more information on invasive species please refer to:
- Pejchar, L., Mooney, H.A. (2009). Invasive species, ecosystem services and human well- being. Trends in Ecology and Evolution, 24(9), 497-502.
- Raghubanshi, A.S., Rai, L.C., Gaur, J.P., Singh, J.S. (2005). Invasive alien species and biodiversity in India. Current Science, 88(4), 539-540.
- Hoddle, M.S. (2004). Restoring balance: using exotic species to control invasive exotic species. Conservation Biology,18, 1, 38-49.
- Brown, J.H., Sax, D.F., (2004). An essay on some topics concerning invasive species. Austral Ecology, 29, 530-536.
For more information on GSOB please refer to:
- Coleman, T.W, and Seybold, S.J. (2008). Previously unrecorded damage to oak, Quercus spp., in Southern California by the goldspotted oak borer, Agrilus coxalis Waterhouse (Coleoptera: Buprestidae). The Pan-Pacific Entomologist 84(4), 288-300.
Coleman, T.W., Grulke, N.E., Daly, M., Godinez Cesar, Shilling, S.L., Riggan, P.J., Seybold, S.J., (2011). Coast live oak, Quercus agrifolia, susceptibility and response to goldspotted oak borer, Agrilus auroguttatus, injury in southern California. Forest Ecology and Management, 261, 1852-1865.
Coleman, T.W., Jones, M.I., Smith, S.L., Venette, R.C., Flint, M.L., and Seybold, S.J. (2015). Goldspotted Oak Borer, Forest Insect & Disease Leaflet 183, Forest Service
Hagen, B.W. (1990). Keeping native California oaks healthy. Tree Notes nr. 7. California Department of Forestry and Fire Protection.
Pictures on this page were retrieved from: www.gsob.org
For more information on invasive species please refer to:
- Pejchar, L., Mooney, H.A. (2009). Invasive species, ecosystem services and human well- being. Trends in Ecology and Evolution, 24(9), 497-502.
- Raghubanshi, A.S., Rai, L.C., Gaur, J.P., Singh, J.S. (2005). Invasive alien species and biodiversity in India. Current Science, 88(4), 539-540.
- Hoddle, M.S. (2004). Restoring balance: using exotic species to control invasive exotic species. Conservation Biology,18, 1, 38-49.
- Brown, J.H., Sax, D.F., (2004). An essay on some topics concerning invasive species. Austral Ecology, 29, 530-536.
For more information on GSOB please refer to:
- Coleman, T.W, and Seybold, S.J. (2008). Previously unrecorded damage to oak, Quercus spp., in Southern California by the goldspotted oak borer, Agrilus coxalis Waterhouse (Coleoptera: Buprestidae). The Pan-Pacific Entomologist 84(4), 288-300.
Coleman, T.W., Grulke, N.E., Daly, M., Godinez Cesar, Shilling, S.L., Riggan, P.J., Seybold, S.J., (2011). Coast live oak, Quercus agrifolia, susceptibility and response to goldspotted oak borer, Agrilus auroguttatus, injury in southern California. Forest Ecology and Management, 261, 1852-1865.
Coleman, T.W., Jones, M.I., Smith, S.L., Venette, R.C., Flint, M.L., and Seybold, S.J. (2015). Goldspotted Oak Borer, Forest Insect & Disease Leaflet 183, Forest Service
Hagen, B.W. (1990). Keeping native California oaks healthy. Tree Notes nr. 7. California Department of Forestry and Fire Protection.
Pictures on this page were retrieved from: www.gsob.org