Yes, pole barn posts can rot. The wooden posts are set into the ground making rot very common. There are measures you can take to prevent rot. Oxygen and moisture can cause rot. You can't eliminate oxygen from your pole barn but you can protect it from moisture. In addition, you should inspect your pole barn and post on a regular basis. Holes, cracks, termites, and carpenter ants can be a sign of fungi which will cause wood to rot. If you see signs of rot, you should address it right away. Ignoring signs of rot on your pole barn can destroy the posts and cause the structure to collapse. This can be extremely dangerous and more expensive than fixing the rot in a timely manner.