And maybe some basic wood rot as well
Rachel, I doubt you have any real wood beetle issue here, although there may be some present. The issue is because of the rot attracting insects. These holes can be caused by all sorts of reasons. Ants, beetles just to name a few.
It appears that the deck is in direct contact with the corner trims of the house? when repairing there should be a small gap to allow air to move between the trim and the decking. This helps this area to dry out after rains and allows access to the paint brush when its time for a paint job.
It also appears that this was repaired once before in the past.
Regardless if you have these bugs or not, you should remove the rot damaged wood and replace. I would suggest that you remove the entire corner section and not just patch the damaged area. This will expose the whole corner area, remove any insects if indeed this is an active infestation and provide a much better repair.
I would also suggest that you get a non-rotting type of trim installed. This will assure that any bugs that were attracted to this type of damage will not return.
Lastly do not treat until the damaged material is removed and discarded. Then re evaluate the need to treat. My thoughts you will not need to do anything else. And be sure to paint both sides of the trim, before you replace it. Makes the wood trim last a much longer time and helps prevent insects eat into the wooden surface.
There are four main types of woodboring beetles. To determine if its true and the type there are some important issues. What type of wood is it. How big are the holes, what does the sawdust or wood shavings look like. If you google powder post beetles you can get some more info.The main types are anobiod, bostrichid, lyctid and false powder post beetle. They work very slowly and are difficult to control once they are in the wood. The method of controls vary but can range from Fumigation to borate treatment. It looks more like carpenter ants but I cant tell from the picture, do you see any large black or black and red ants coming and going from the area. Or is there any dirt or mud tubes in the wood. Go to Kellerpest.com and look at our pest library and the termite and carpenter and info. also check out the wood destroying insect links. If you can remove the old paint so I can see the wood I will be better abler to help you.
Thank you thank you. You just told me more than anyone else. So I need to call my termite guy and have him come take a look? I will let you know what he said.