Continued
To treat a mature nest takes expertise, it is a risky business especially if it is sited in a roof void. In my years in pest control I can honestly say that I have done some ducking and diving in my time. These days pest controllers are equipped with lances, some of which are up to 14 feet in length, these lances fire insecticidal powder into nests under the driving force of compressed carbon dioxide. These insecticides are mostly carbamates, a sort of powder form of nerve toxin, these are quite residual and normally not available to the public. Pest controllers also have rapid knockdown liquid insecticides which are quite expensive but very effective, again not normally available to Joe Public. The best idea at the end of the day is to get in a professional.