Mosquito Control In Rain Barrels: How To Control Mosquitoes In A Rain Barrel

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By Mary H. Dyer, Master Naturalist and Master Gardener

Harvesting rain in barrels is an earth-friendly practice that conserves water, reduces runoff that negatively impacts waterways, and benefits plants and soil. The downside is that standing water in rain barrels is an ideal breeding ground for mosquitoes. There are a number of ways of preventing mosquitoes in rain barrels. Read on for a few helpful suggestions.

Rain Barrels and Mosquito Pests

While using a rain barrel in the garden is great for water conservation among its other benefits, mosquitoes are a constant threat, as they carry life-threatening diseases. Learning how to control mosquitoes in a rain barrel is just as important to controlling them anywhere else, especially since the pests take advantage of standing water to help carry out their life cycle.

Here are some things you can do to minimize their presence:

Dish soap – Liquid dish soap creates a slick film on the surface of the water. When mosquitoes attempt to land, they drown before they have time to lay eggs. Use natural soap and avoid products with perfume or degreasers, especially if you water your plants with rain water. One or two tablespoons of liquid soap per week is plenty for most rain barrels.

Mosquito dunks – Also known as mosquito donuts, mosquito dunks are round cakes of Bti (Bacillus thuringiensis israelensis), a naturally occurring bacteria that provides mosquito control in rain barrels as it slowly dissolves. However, it is safe for beneficial insects. Be sure the product label indicates the dunks are formulated for ponds because other types, which kill caterpillars, aren’t effective in water. Replace the dunks as needed. Check them after a hard rain.

Vegetable oil – Oil floats on the surface of the water. If mosquitoes attempt to land, they suffocate in the oil. Use about a quarter cup of oil per week. You can use any type of oil, including olive oil. Horticultural oil or dormant oil are also effective for preventing mosquitoes in rain barrels.

Netting – Fine mesh or netting attached firmly to the barrel keeps mosquitoes out. Attach the netting to the barrel with a bungee cord.

Goldfish – One or two goldfish keep mosquitoes in control and their poop provides a little extra nitrogen-rich fertilizer for plants. This isn’t a good solution, however, if your rain barrel is in direct sunlight or the water is too warm. Be sure to place netting over the spigot and any other openings. Remove the goldfish and bring them indoors before the first hard frost.

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