Having said that. pests problems fall into three categories.
Here are some examples:
1) A wasp nest is found in a wall. Clearly not the fault of the owner, and clearly can be dealt with. So a guarantee would be reasonable for the reported pest treated in that location.
2) Occupants complain about bed bugs. Bed bugs are travelers and are brought into the house by visitors. The more visitors you have the more the chances of infection. So for example in a rented property this would fall into the category of "Occupational Hazard" and after the initial treatment, would be impossible to give a guarantee.
3) The last one is negligence on the part of the owner. For example there is no reason why you should have mold, rot, cockroaches, fleas, mice or rats, woodworm , termites or ticks in a house. All these are avoidable if normal precautions (filling holes, fitting mosquito netting, fixing leaky roofs etc are taken by the owner.
It is therefore beyond our control to guarantee the activities of any pests on a day to day or week to week basis, and this is especially the case where structural or repair work, plumbing or electrical work has been carried and not completed to a professional standard, out or where the owner leaves cat food or dog food lying around for pests to find. And we certainly cannot guarantee the movements or arrival of pests from neighboring properties, fields, other streets or guests arriving/staying at the property.