Water Blog

News, notes and thoughts from Blue Water Baltimore.

How to Keep Your Rain Barrels Free of Mosquitoes

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Your rain barrel is designed to keep mosquitoes out, but there is no guarantee that these pesky creatures won’t find a crack in the system.

The fail-safe way is to drain all of the water within five days of the rain barrel filling up. This solution not only eliminates standing water, but it ensures that the next time it rains the rain barrel will be empty and can reduce runoff, one of rain barrels’ main purposes.

If you’re holding onto your water for more than five days, there are three eco-friendly options that Blue Water Baltimore recommends for eliminating mosquito breeding which are safe for your family and the environment.

With our new design, however, you may also remove your filter screen and simply screw in your sealant cap. Be sure to remove and replace with your screen before the next rain!

Liquid Dish Soap

Use one tablespoon once a week or after each storm.

The soap creates a film on the surface of the water, breaking the surface tension. Therefore, if mosquitoes make it into the barrel to lay their eggs, they drown before they get a chance. Use ecofriendly liquid soap to prevent additional pollution and prevent damage to your plants if you use your harvested water for irrigation.

Mosquito Dunks

Use one 1 dunk once a month or as needed.

Dunks are made of Bacillus thuringiensis israelensis or Bti, a bacteria that kills the mosquito larvae (as well as black flies). The product slowly dissolves, releasing the bacteria for continuous mosquito control.

There are other bacteria based mosquito control products sold under different names. If you are shopping around, look for the Bti ingredient.

Each Blue Water Baltimore rain barrel comes with one free Bti dunk to get you started.

Vegetable Oil

Use ¼ cup once a week or after each storm.

The vegetable oil will float on the top of the water in your rain barrel, suffocating the mosquito larvae, should mosquitoes lay eggs in the water.