Ed from Nc writes
They have attacked wild magnolias (also called bay magnolias or redbay trees)
Unfortunately, insecticides like Zylam or any other systemic products are generally of no use to treat ambrosia or other boring beetles in trees. These beetles will not ingest the active ingredient, and trees infested with these insects are often already weak from disease, drought, other conditions before the beetles infest them. You can try trimming and destroying infested branches and spraying nearby susceptible trees with a preventative insecticide such as Talstar P. Fully infested trees will usually need to be removed and destroyed.
Answer last updated on: 10/19/2016