Santa Clarita Valley oak trees are being invaded by the goldspotted oak borer; an insect named for its iridescent black shell with gold spots that burrows underneath the bark of oak trees.   Cristhian Mace, a natural areas biologist with the L.A. County Department of Parks and Recreation, said May was the first time she heard about the goldspotted oak borer.   “It has been this whirlwind roller coaster of catching up and learning and joining as many committees as possible to be on the front steps of this emerging issue,” said Mace.   The insect has been labeled an invasive species to the area because of the “ecosystem havoc” it is creating by destroying oak trees. Mace said the insect is native to Arizona and northern Mexico areas but first appeared in San Diego County in 2004.   Since then, the goldspotted oak borer has made it was up through Southern California. It was found in Green Valley and successfully mitigated by CalFire, according to Mace.  First diagnosed oak tree infested by the goldspotted oak borer in Green Valley. Courtesy of Cristhian Mace. In Santa Clarita, infestations have been found in East Canyon, Rice Canyon, and in 2019 there was evidence found in Whitney Canyon, said Mace.   Frank Hoffman, recreational services supervisor at the Placerita Canyon Nature Center, said the nature center recently had two surveys done of its oak trees that showed there was no evidence of the goldspotted oak borer in the canyon.   “We’re happy to say that as of our first two surveys of the park, one in and around the immediate picnic area, and then in and around our parking lot was the second survey, and then up and down a part of our ecology trail, we have found that there is no evidence of that little guy being here yet,” said Hoffman.   Mace said Whitney Canyon is about a mile away from Placerita Canyon and with the multiple areas starting to show infestations, it puts L.A. County natural areas at the front of this issue, and it is important to be proactive.   There are four species of oak trees the insect has been affecting: the coast live oak, California black oak, canyon live oak, and the Engelmann oak, according to Mace. The coast live oak is the primary species of oak tree in the Santa Clarita Valley and the species of oak tree that has been the most affected, said Hoffman.   “They are overwhelmingly affecting coast live oaks, and we even see them affecting canyon live oaks, but to a much lesser degree,” said Mace. “We’ve seen them infesting Engelmann oaks, but the Engelmann oaks are showing more resistance. It’s really the coast live oaks that are being decimated.”  Image of a Coast Live Oak tree killed by goldspotted oak borer. Courtesy of Cristhian Mace. Mace said the No. 1 way these insects have been spreading is through the transportation of firewood – people are transporting the goldspotted oak borer from a place of infestation to an area that did not have the insect originally.   Mace said the goldspotted oak borer was exhibiting interesting behavior because a pest typically will go for the weaker species, but the female goldspotted oak borer will choose a healthy oak tree to burrow under its bark, lay her eggs and then the larva will live off the nutrients that are being transported underneath the bark to sustain the tree.   “These mature trees offer more flow (of nutrients), more real estate, and more protection for them,” said Mace.   When the insect is ready to leave the tree, it burrows out a 2-4 millimeter D-shaped hole, which has become the tell-tale sign that there was an infestation, added Mace.   She recommended that if residents who have oak trees in their proximity want to start examining their trees for infestations, they have to start at the base of the tree’s trunk.   “The majority of exit holes are within the bottom 2 feet of the tree, and the more infected the tree is, we see the holes gradually work its way up the tree,” said Mace.   Mace added that other ways to tell if a tree has been infected is that the canopy of the tree will begin to die back and thin out, so there would be less leaves or very brown leaves. There would also be staining on the bark, which looks like black discolored drips coming down the trunk.  A few studies, according to Mace, have shown that infestations can be managed when there are only two to 10 holes found in the tree. When there are 10 to 25 holes, the tree is considered to be in “dangerous territory” and if there are more than 25 holes counted, the tree is considered a “goner” and the best action to take is removing it.   “If folks are noticing that there are exit holes on oaks on their property or in wild space, they can call the pest hotline at 1-800-491-1899. They can also visit the California Department of Food and Agriculture web page (www.cdfa.ca.gov/plant/reportapest/) to report a pest,” Mace said.   The biggest proactive step people can take is to not transport contaminated firewood, both Hoffman and Mace said.   Mace recommended that “you burn where you buy.” She said buying firewood from local certified stores typically means the wood has been seasoned or heat-treated for two years to make sure the product does not have any contaminants in it.   Mace said that this invasive insect is on a lot of people’s radar now and to manage it, they are planning to conduct annual surveys to monitor where infestations are popping up.   The post SCV oak trees threatened by invasive goldspotted oak borer  appeared first on Santa Clarita Valley Signal.