There is no more accurate description of Asian Ambrosia Beetle damage than “Toothpicks coming out of the trunk of my tree!”
This boring pest came to my attention in 2001 when a big flowering cherry tree in my back yard just “up and died” one April. I found the toothpicks when I examined it.
The tiny female beetle bores into the trunk of susceptible trees (crape myrtle, redbud, dogwood, cherry, etc.) in early spring and deposits her eggs. Lovingly she leaves a deposit of ambrosia fungus in the hole, to provide a first meal for the larvae when they hatch. Unfortunately, the beetle fungus is usually contaminated with other, more virulent, fungi – which often lead to a tree’s demise.
There is no treatment for an Asian ambrosia beetle attack once seen. The fungus inside the tree can not be eliminated.
Asian ambrosia beetle is serious pest. Once it attacks a tree typically the only option is to see if the tree survives the summer. If not, cut the tree down and destroy it or remove it from your property. Crepemyrtles might resprout and grow another trunk to replace what you remove but most other trees do not respond so nicely.
If you notice the “toothpicks”, your best bet is to spray susceptible trees each spring with cypermethrin ( click for sources), permethrin (click for sources) or deltamethrin (click for sources) in order to protect them from female beetles landing on the trunk and boring in.
To know when to spray, you can build a trap to monitor their emergence in early spring (mid-February).
These two Extension reports give a good overview.
ambrosia beetle on crapemyrtle