Hi wellygirl2. holey potatoes can be caused both by slugs and wireworm. If the holes are right through then wireworm could be your problem. are you growing on ground which was previously grassland? this is usually a known wireworm breeding habitat. If this is the case and your ground is now in constant use and you are rotating your crops then you will eventually break their life cycle and they will either move on or die off from your ground. Try to prevent slugs with your preferred method as some people do not like to use pellets. Hope this helps and good luck.