Our back 'patio' consists of stone slabs sitting on a raised sand bed. Over the last 10 days a whole bunch of carpenter bees (about 1.5 inches long) have started to burrow down into the sand between the tiles. It is resulting in unsightly mounds of sand all over the patio & we can't use the area for fear of being bombarded by these big bees. I have tried to zap bees individually with bee killer spray as they land, but this guerilla tactic is highly inefficient. Is there any thing I can pour on the sand itself to make them go away? thanks for your help.