You must fill the trench back in after using
Termidor SC and the back fill should also be treated. If you leave the treated trench exposed, then it will be constantly exposed to the sun and the
Termidor SC will degrade faster. Also, the termites would have to tunnel deeper than the they normally would because there would be no soil for them to travel through, which means they could travel through untreated soil. It is always important to read and follow the
product label. Manufacturers do a lot of research and development so that they can tell you the most effective way to use their product. Failure to follow the instructions will no doubt give you sub par results.