Mosquitoes and rain barrels

So if you are like me you have a 5 gallon pail, 30 gal barrel or a 55 gal barrel collection rain water to tend to the garden or even your lawn.  And with the rain we have had in the past two weeks in the Capital District, it only takes a short time to fill them up if the are attached to a gutter.  It also takes even less time for mosquitoes to turn around and create a filled drum of larva.

Not something we want to see, or have.  So what to do to keep those pest at bay?

If you are attached to your gutter system to collect rain water, you will first need to make sure the gutters are properly pitched to prevent standing water to build up in your gutters.  It takes only a tablespoon of water for a mosquito to make it a breeding ground, then when it rains those little larva now are washed into the collection system.

There is also a school of thought, and I will cover that now so that we can get on to some other solutions and that is to add bleach to the barrels.  The problem with that is that there is a fine line to sterilizing the water with bleach and making it a dangerous water mixture that will kill your plants and bacteria in the soil.  With chlorine bleach there is a safe amount to use to make water safe to drink and if you use to much it could make you very ill or even cause death.  You also need several hundred gallons of water to measure correctly.  That being said you also need to let the water be exposed for 24 to 48 hours to UV lighting to "burn off" the chlorine.  If you mixture is wrong...it could still be dangerous for the soil and plants or if the exposure and mix were off the mosquitoes will be right back there.  A tough catch 22 so we advise to makes sure any product you use does not contain any chlorine bleach...period.

So here are some ways to curb mosquitoes in your rain barrels:

1. Put a goldfish or two in the barrel. I especially like this one because of the happy little ecological world it creates. The fish eat the mosquito larvae and then poop out beneficial elements (mainly, nitrogen) for your garden. Things to remember: leave enough of an opening so that the fish can receive oxygen from the surface, and take the poor guys out before the first frost!

2. A thin layer of vegetable oil on the surface of the water can prevent mosquito larvae from clinging to the surface, which is how they breathe. The oil slick will also serve as a barrier for insects to enter the water. Do not use this method with goldfish because it blocks the availability of oxygen also remember that if your barrel over fills, the oil will run off.  This method is best if you do not use your barrel water regularly and it may sit for a few days before the the next rain.

3. Filters - cover the intake with a piece of old nylons or netting. You will need to clear out the filter regularly and ensure that there are no holes for insects to pass through.  This would also include adding a screen or old sheet cover to your rain barrel.

4. Barley Mosquito Dunks - read the labels carefully, not all dunks are chemical free and I can not promote a specific manufacturer.  I am still searching for a How to, so you can make your own but one I do have requires a cup a just harvested barely, the whole plant, minus the roots, lightly shredded and place in a stocking or cheese cloth, tied up and thrown in to the rain barrel.  As it breaks down in the water, Bacillus thuringiensis israelensis (Bti) is released, this is toxic to the larvae but safe for everyone else.

Love to hear your suggestions as well.