If it is a pest problem then you probably have carpenter ants. Carpenter ants both produce frass, which can often be confused with sawdust, but there is a difference. The trick is to look closely at the “sawdust”. They actually produce tiny pellets which are usually beige or brown (but the color is in relation to the wood they eat). This will look like piles of sand but from far could look like sawdust as the pellets are roughly the size of ground pepper. Carpenter ants produce frass which looks like sawdust. Carpenter ants do not eat wood; instead they chew it and remove it from their den to create their homes.
No. Poisoning is not recommended as a way to get rid of rodents. This is because the poison will take some time to kill the rodent and it will most likely die where it hides. Thus, poisoning leads to dead rodents in the walls and under the floors. These bodies will decompose and need to be removed, which will only be possible by ripping open the floor and walls.
There are many different ways to reduce a bug issue.