Treating Rain Barrels for Mosquitoes
We use the blue or white 55 gallon commonly found plastic barrels similar to the ones pictured. They are mounted beneath our chicken coupe, each fed from a downspout. If you have your barrels outside during periods of dry weather, still standing water is an inviting little breeding ground for mosquitoes.
You can always drain the barrels if you don’t plan on using them, however if you are determined to only use rainwater for your gardening needs you really don’t want to chance dumping the water and then running short later on. I found a simply and quick solution was to just cut screens and install over the open tops. Less than $10 bought a roll of screen door material from the local hardware store. I cut them slightly oversize and secured them with twine on some and bungee cords on the others. The screens not only keep the bloodsuckers from setting up shop, they greatly filter the runoff and keep the gunk out of the barrel.
Mosquito “dunks” are also a handy and inexpensive solution. They can usually be found in packets that will last you the summer, depending on how many barrels you want to treat. You simply drop one in and voila. They will not harm your plants. Another method that won’t require you getting into your car and driving anywhere is to add a tablespoon of liquid dish soap to the water. The soap will stay on the top of the water and create a barrier that will kill any mosquitoes before they can lay their eggs. FYI, do not use the store bought off the shelf type soaps unless it is 100% organic or environmentally friendly. Products like Dawn are harmful to plants and vegetation. Another item found in most cupboards is vegetable oil, also highly effective for killing the larvae. Depending on the size of the barrel, usually just enough to cover the surface of the water, maybe 1/3 cup, will suffocate the little buggers.