An efficient way to control mosquitoes is to find and eliminate their larval habitat .Eliminating large larval development sites (source reduction) such as swamps or sluggishly moving streams or ditches may require community-wide effort. This is usually a task for your organized mosquito control program. They might impound an area of water, establish ditches or canals or control the aquatic weeds (cattails, water lettuce, etc) on a body of water. The second method used by organized mosquito control agencies is larviciding. This utilizes the application of insecticides targeted at the immature mosquitoes - the larvae or pupae. These are applied to bodies of water harboring the larvae. However, since larvae do not usually occupy the entire body of water, larvicides are applied where the larvae are, usually the areas near the shoreline of the lake, stream or ditch. Larvicides differ from adulticides in that they are directed at a limited targeted area, i.e. the body of water and often only that area where the larvae grow and mature.