Ticks will not get into a closed screened tent with floor, unless they hitch a ride in on your clothing. They certainly aren't going to bite through the floor! Scorpions can't get in, either, and insecticide won't do much to them anyway. Spraying the tent and ground sheet is a waste of money and an unnecessary exposure to the chemicals. Maybe spray the netting screen door, but not anything else.

The only time you would want to spray a ground sheet is if you have a floorless tent with no screening. In that case, of course, the crawlies can enter freely. If you have problems with ticks and scorpions (and ants), you definitely want an enclosed tent.

Actually, ticks are not insects; they are arachnids, like spiders. Not that this relationship makes them any more likable!