Q: What is the best systemic insecticide for ambrosia beetle control on crepe myrtles? I was using Isotox but my bottle is all gone.

A: Systemic insecticide will not kill ambrosia beetles. The female beetle bores through the bark and into the heartwood of crapemyrtles. Though systemic insecticide may be in the cambium layer of the plant, the beetle does not ingest this vascular tissue: she quickly bores through it and is not exposed to enough insecticide to hurt her. The best way to protect crapemyrtles from ambrosia beetle attack is to thoroughly spray the bark with cypermethrin, permethrin or deltamethrin four times at two week intervals in spring. Beetles begin to be active in February so don’t delay your sprays.