From a programming standpoint the answer is no. The only way to get the bots out would be to have a page before the forum whereby a code is entered manually. You may or may not have seen them before where they say 'enter the code in the box' and the code is written in a way that cannot be identified as the letters that they are. IE: Only human intelligence could tell what they are.
Doing that would filter out the bots, but would be time consuming for everyone on the forum.