They actually make a caulk for goiing around ridged foam. I think the stuff in the can spay is open cell?
I only use the "Great Stuff FireBlock Foam" it is both closed cell, water resistant, has very good adhesion holds the rigid foam VERY tightly, good insulation and is fire resistant to boot.
Also one 16oz can does the same job of 20+ tubes of caulk.
Make certain that you use some kind of glove when you use this foam, if you get it on your skin it is THERE until it wears off days later, nothing takes it off.
http://building.dow.com/na/en/products/sealants/fireblock.htm
I spray foamed ALL of my polyiso insulation around the top and both sides behind it at least an inch or two, left the bottom unsealed just in case any moisture gets behind the insulation its not trapped and can just drip to the ground under the polyethylene.
I left a 1/4" gap in between the foam sheets and filled it with the fireblock foam to make a tight seal, since the edges are bare foam the adhesion is rock solid and virtually forms one solid sheet, then I trim the excess off flush and then tape over it with high quality aluminum tape Nashua Cold Weather.
So it is literally like one solid sheet of 2" thick R13 foam around all the perimeter walls.
I used the fireblock foam to also seal every point where plumbing pipes, electrical wires, HVAC ducts and floor registers go through the floor, plus on the thin metal registers I completely covered them in about 2" of fireblock foam so no metal is exposed. They should really make these registers double walled polypropylene with insulation in between, pretty stupid to make them out of thin galvanized metal that sweats like crazy.
I also covered the cement block and brick walls with boric acid powder prior to installing the foam boards that should keep any possible bug problems at bay at least for a few years.
It is so dry under there now I don't think there is much chance of any termites, especially since even when it was a rain forest cave hot and humid and dripping wet we never had termites for the 20 years we have lived here which is surprising since many of our neighbors have had termites and we certainly had prime conditions for them before the encapsulation.
Top pic is what one corner looked like when I started, after repointing and then covering with 3 coats of the Portland Sunny Dry waterproofing, one end of the French Drain is seen and you can tell the soil is soaking wet and insulation in the joist is worthless wet manure.
Bottom is what that same corner looked like after encapsulation.