Since we do not recommend that ground-nesting bees be eliminated, we don't have a particular suggestion for getting rid of them aside from the method you already mentioned -- increasing the density of the turf, since ground-nesting bees rarely tunnel into thick lawns. Ground-nesting wasps, on the other hand, might be less picky about nest site, so it's hard to guess which you have present in the yard. Cicada Killer wasps are active now, but so are some species of ground-nesting bees as well as several other kinds of wasps, like those that prey on Japanese Beetle grubs in a lawn. Both groups would be vulnerable to wasp spray or dust type of insecticides, though each nest hole would need to be located and spot-treated, and the chemicals used in those types of insecticides (often pyrethroids) affect any insect they come into contact with, including beneficial species that prey on pests.

Using a sprinkler on lawns that often does risk outbreaks of turf fungal infections and can reduce the drought tolerance of the grass. Usually it also deters nesting by ground-nesting bees (though perhaps not wasps), though obviously in this case it hasn't. Short of killing them with pesticide applications, tilling the soil (which would also kill them or their eggs in the burrows, if it were practical to till an established lawn), or flooding them out with excessive irrigation, there is no other way to deter them from nesting in a chosen site.

Miri

Miri,