Hello!
There’s some good news and some bad news. It looks like your pest problem is a termite. The good part is that they won’t harm your plants, because they feed on decaying wood, not living plant material. The bad news is that your wood banister is probably being munched on. The best thing to do would be to check out our termite control page and see what works best for you.
https://www.planetnatural.com/pest-problem-solver/household-pests/termite-control/
The Difference Between Termites and Ants
• Termites have relatively straight antennae.
• Ants have elbowed antennae.
• The termite abdomen is broadly joined to the thorax — no waist.
• Ants have a narrow waist and appear segmented.
• Termites have two pair of wings (front and back) that are almost equal in length.
• Ants have two pair of wings — the front wings are much larger than the back wings.
Best of luck!