You are not only drilling through just the concrete here, but also as deep as you can into the dirt. The deeper the better. Once the holes are drilled, you fill at the same rate you did the trench, 4 gallons per 10 feet. If you drilled the holes 12 inches apart, then you would have 10 holes over 10 feet that you are trying to fill with 4 gallons. This works out to be a little less than half a gallon per hole. To fill these I would recommend using the one gallon sprayer on a "pin stream" setting so you can force the liquid down the hole and not splash it everywhere. You can also use a funnel and pour the termiticide down the holes. It is difficult to get 4 gallons per 10 feet in the holes, so it is important that you use a long drill bit, at least 18" long so you can bore out enough dirt to hold the termiticide. Sometimes the ground is slow to soak up the termiticide you place in the holes. You may need to fill the holes, then go work on something else for an hour, come back and fill them again, go work on something else... 3 to 4 times to get the proper amount down the holes. Once the holes are filled all you need to do is patch them with a concrete patch filler you can buy at a home improvement or hardware store or you can use our Trebor plugs that will close the hole with no concrete mess.
Termidor SC is used for both termite prevention as well as ant control. The termite prevention requires the trenching and rodding, and is done once every 10 years. When using it for ant control, you would spray 1 foot up the side of the structure and 1 foot out into the soil, all the way around the perimeter of the structure, along with around doors and windows. This can be done according the following label instructions:
Depending on how heavy the rain was will depend on if you will need to reapply. If the rain was only light and you had just completed a Termidor treatment in a trench for termite prevention then you should be fine. If it was a heavy rain for a long period of time then you may need to reapply. If you were using the Termidor to spray around the perimeter of your home for ants and general insects, then you will likely need to reapply it on a day when no rain is expected for at least 24 hours.
Per manufacturer, the most effective termite treatment would be digging the 6in x 6in trench around the foundation and applying Termidor SC per label. If the gap is close to the suggested trench requirements, we do not see where this would not be as effective.