Curious , So just to be sure this is a single family home and how far apart from neighboring homes is it ? ( wondering it it was like my first house that was maybe four to four 1/2 feet from the neighbor home) it its enough of a distance from neighboring homes with this current tenant being behind it may be a better choice to just cut your losses and evict based on non payment and live with the cost of treating your unit once its empty, As to the bugs them self , with your tenant having lived there for three years those bugs had to be brought in to the home by something they brought home and that might be that they were guest in a home that had them and accidently carried the into the house . If these tenants had only lived there a short time it would be harder to figure out if they were left by a previous tenant or introduced by the new tenant .. figure it out, meaning what are the odds they would actually get the rent caught up and be able to pay you for extermination ? BTW taking a tenant to court for unpaid rent when they are behind is not retaliation