The Garden Bug: Killing mosquito larvae in standing water
By Brenda Weaver
Add apple cider vinegar to standing water at a ratio of about 15% vinegar to 85% water. Larvae die within 18 hours.
Add one tablespoon vegetable oil or olive oil per gallon of standing water; the surface is coated and larvae suffocate.
Add a drop or two of dish soap per gallon of standing water; this also coats the surface and suffocates larvae.
Mosquito "dunks" contain Bti, which is safe for people, pets, and other animals and insects. When added to standing water and eaten by larvae, it kills them.
Source: mosquitomagician.com