What measures can be taken to eradicate the mosquito larvae?
The usual, traditional method of eradicating mosquito larvae is through the application of insecticides. However many of these are known to have severe negative effects on water quality, particularly through being non-selectively toxic and therefore killing lots of other aquatic life as well as the mosquitoes. Moreover, some are known for their effects on animals further up the foodchain; the most famous example of this being DDT, which was used to kill adult mosquitoes. It was discovered that this pesticide resulted in birds laying eggs that had very thin shells, preventing the chicks from hatching successfully. As such, it was banned in most developed countries. Modern insecticides used for mosquito larva reduction have been developed to target mosquitoes specifically; a popular one in the USA is methoprene, which interferes with the mosquitoes’ growth hormones, preventing development into adults. Microbial compounds, which are not dangerous to other organisms, are also sometimes used.
Another approach is through the use of natural enemies of the mosquito larvae, notably certain species of fish and dragonflies. These will eat mosquito larvae and pupae, thus naturally reducing numbers, and with little undue effect on water quality (although in some contexts, such as reservoir water, there may be concerns with stocking the water source with large numbers of fish).