Phytophthora ramorum infection of some oaks and tanbark oaks have been accompanied by increased incidence of oak bark beetle and oak ambrosia beetle outbreaks. The effects of these beetles preventing emergence from the infested oaks and averting their destructive activity in the adjacent trees is the objective of this study.
In June 2000, three 40 cm long bolts were removed from eight heavily infested coast live oaks Quercus agrifolia, and one black oak Q. kelloggii in the following sequence: the first bolt 1 meter above the ground, the second one under the main limbs’ crotch, and the third one from a 3-inch diameter branch. Each bolt was then cut vertically into two halves. One half was selected at random and its bark surface sprayed with Permethrin, while the corresponding other half (control) was not sprayed. Bolt halves were placed into separate air-conditioned rearing cans to collect daily emerging beetles.
The results showed that Permethrin significantly reduced emergence of both the oak ambrosia beetle, Monothrum scutellare, and the oak bark beetle, Pseudopityphthorus pubipennis from the treated logs (a = 0.05).
