Livestock watering troughs can be a breeding site for mosquitoes. Regular weekly flushing / cleaning will make troughs less attractive to female mosquitoes searching for places to lay their eggs. Somewhat stagnant water with a few dead leaves, grass clippings, or some algae provides food for the microorganism that mosquito larvae eat. Keeping the water fresh and clear should mean fewer developing mosquitoes.
Make sure shut-off valves are working in automatic waterers and that there is a pad or good drainage area. Wet spots around water tanks provide good breeding sites for mosquitoes and biting gnats.
Management with Insecticides
Two types of insecticides are labeled for control of mosquito larvae in a variety of contained and standing water sites, including animal watering troughs. Donut and pellet formulations of Bacillus thuringiensis israeliensis (Bti) or small blocks containing the insect growth regulator methoprene (Mosquito Torpedo) are widely available. Dosage is based on square feet of water surface area.
By Lee Townsend, Extension Entomologist