When using Termidor SC for ant control, you want to make sure the ants are contacting the treated area. If they are traveling on top of the rock and fabric topical application is fine. If not, you would need to take the material back and then apply and replace.
It is not recommended to use Termidor SC with rock, granite, or gravel. Termidor SC is made to bind to soil molecules which allows it to last for 10 years, whereas Termidor applied to porous surfaces such as rock, granite, gravel, or other material will only last and remain effective for a few months. You should dig a trench in the soil against the foundation and/or drill through concrete to apply. Please take a few moments to review our article on How to Treat for Termites for a successful application. Please let us know if you need anything else.
The trench should be filled back with the soil you removed to create it so that it can be treated and create the area termites will go through to contact the Termidor SC. It will last 10 years or more in the soil.
Drywood termites are all contained in a piece of wood. They do not go back to the ground like subterranean termites. For Termidor to work on drywood termites, you have to drill directly into the piece of wood the termites are in and inject Termidor into the wood. Termidor does not penetrate into wood, so you have to inject it into the center. It has to touch the termites to work, but the benefit is that it only has to contact a few termites, and then they can pass it on to the rest of the colony. To treat for subterranean termites using Termidor, you will need to trench all around the skirt just like you would around a home's foundation, and then you will need to trench around all of the blocks that are holding the trailer up, just like you would a home's piers in a crawlspace.
It would be a great benefit to add a barrier spray outside using Termidor SC.