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Invasive Insect Profile: Gold Spotted Oak Borer & Shot Hole Borer

Invasive Insect Profile: Gold Spotted Oak Borer & Shot Hole Borer

One thing that Irvine Ranch Conservancy is working to control to keep native habitats thriving on the Irvine Ranch Natural Landmarks are invasive species, both plants and insects. The Gold Spotted Oak Borer (GSOB) and the Shot Hole Borer (SHB) are two invasive beetle species that are found in Southern California and threaten Orange County native environments. 

While these two species share some similarities, they also have distinct differences that make them unique. Understanding these invasive insects can help with managing their population on the Landmarks.

Similarities:

  • Tree Infestation: The GSOB and the SHB are invasive beetles that infest trees, causing significant damage to their hosts.
  • Boring Behavior: Both insects make tunnels or holes within tree trunks and branches to lay eggs and take care of their larva. This critically impacts the health of infested trees.
  • Tree Species Preference: Both bugs go after different types of oak trees, however, the GSOB mainly attacks red oak trees, while the SHB has been seen on many different types of trees like avocado, box elder and sycamore.

 

Differences:

  • Native Origin: While both pests are currently found in Orange County, the GSOB comes from Southeastern Arizona, while the SHB comes from Southeast Asia.
  • Visual Identification: The GSOB is larger, about 1.25 cm long, and has gold spots on its black wings. The SHB is smaller, about 2mm, and has a reddish-brown or black-colored body that’s shaped like a cylinder.
  • Known Damage: The GSOB damages trees by boring tunnels or holes and feeding larvae which can lead to canopy dieback and tree death. The SHB attacks trees by injecting a fungus into the tree which causes a disease called Fusarium dieback. This disease disrupts the tree’s veins and can cause other problems.
  • Control and Management: Since both pests have different life cycles and behaviors, people must develop different strategies for managing them. Local experts and authorities must work together to stop the spread of the beetle and minimize damage.

While IRC monitors and helps to prevent the further spread of these invasive insects, Orange County residents can also help play a role. With the recent weather, you might be looking to cozy up next to a fire. However, if you don’t ensure that the firewood is local to the environment which it was sourced, it can contribute negatively to the spread of invasive insects. GSOB, SHB and other invasive insects are often introduced to new areas via firewood. IRC wants to remind residents to buy it where you burn it.”

IRC staff survey oak trees for GSOB entry/exit holes.
IRC staff survey oak trees for GSOB entry/exit holes.