Your treatment should not be done within 24 to 48 hours of any rainfall for the best results. Your trench should be 6'' wide, 6'' deep and 10 linear feet along the structure with the Termidor. You can take a look at our site on How to Do a Termite Treatment to give you the proper application instructions for the best results.
Termites do not normally attack live, healthy trees so you most likely will not find any products that will work as a ground barrier around the trees. Most people are primarily concerned with protecting the big investment, their home, and Termidor SCwould be the product to use for that. It is only labeled to be used adjacent to the structure though. Please take a moment to read over our article on "How to do a Termite Treatment" for complete details.
Termidor SC can be used in sandy soil. You would still do the trench and treat the sand 6" x 6" around the foundation as termites will still go through that area to get to your home if looking for food, if this is your target pest.
Termidor SC bonds to the soil and does not move once it is applied. Therefore, it can be applied where a well or garden is present as long as it is more than 10 feet away from the well or garden or tree. We would suggest not applying Termidor SC along the side of the house that is within 10 feet of the trees. You should keep a close eye on this area of the house for termites, or you can of course always install some Termite Bait Stations in that area for monitoring activity.