Some can. Larvicides have different degrees of specificity. Perhaps the most specific is a bacterium called Bacillus thuringiensis israelensis, or B.t.i. for short. It targets certain fly (including mosquito) larvae only and can be applied as pellets called donuts or dunks. However, these should be used only in the absence of natural predators such as dragonfly nymphs. Thus, if effects on desired predator species are a concern, the situation is not appropriate for larvicides. Remember, mosquito larvae are an important food source for many species and if you remove it they may starve to death even if the removal technique itself doesn't kill them. A complete, healthy ecosystem can regulate itself. Total eradication of mosquitos is neither feasible nor desirable. Human behavior modification is the best defense against mosquito-borne diseases.