Leafhoppers are a small flying insect which are often never seen, any damage caused is so minimal that it is generally unnoticeable, and overall there is hardly never any need to control them.
The size of the Leafhopper is the reason why they are so rarely seen, in fact a person needs to get down on hands and knees to closely look at the grass leaf very carefully in order to diagnose they are even there, although they can sometimes be seen hopping when they are disturbed from lawn mowing.
Leafhoppers feed on the leaf blades of grass, but consume so little, and their numbers never seem to ever reach problem proportions that there never appears to be any damage whatsoever to the sod itself.
Leafhoppers are A Natural Friend
It is best to consider Leafhoppers as just another natural part of the ecosystem, and for the lawn owner they are neither friend nor foe, however they will have other interactions within the natural environment which do contribute to their overall place in our natural environments.
There can be no reason to ever control or kill Leafhoppers from thinking they are a pest problem for lawns, because they simply never are, and cause no ill effects from their presence. However, if a person is so annoyed by having a few of these friendly, almost invisible bugs in the lawn, then most general insecticides made for lawn use will work on Leafhoppers too, simply check the product label for details of which insects it will target.