I don't think equating people to mosquitos is a good analogy, it seems dehumanizing the other to me.
But let's roll with it anyway. What we have here is actually a large-scale land owner who leases out the land to anyone without further conditions to the lessee. It would seem silly to blame the leaser and not the lessee for what happens on those lands.
Of course the government can still come in and request that they do something about the mosquitoes, if laws and regulations require that, but until then they won't become active because it would mean going back on their lease agreements which grant the lessee free use.
But let's roll with it anyway. What we have here is actually a large-scale land owner who leases out the land to anyone without further conditions to the lessee. It would seem silly to blame the leaser and not the lessee for what happens on those lands. Of course the government can still come in and request that they do something about the mosquitoes, if laws and regulations require that, but until then they won't become active because it would mean going back on their lease agreements which grant the lessee free use.