Can you use termidor around the perimeter of house that has gravel around edge instead of soil???
Yes. Under the gravel there is no doubt dirt down there at some point. From this dirt the termites can arise and access the home. I've also seen where failure to treat the gravel above the dirt will allow the termites to "bridge" over the treated soil below so be sure to give the rocks a dose of either the Termidor or one of the actives listed below. Just keep in mind the normal residual of anything applied to rocks or gravel won't last nearly as long compared to when it's applied to soil where it's more "protected" from the sun and rain.