As rain barrels become an important part of the garden landscape it can only be expected that they will become magnets for water-loving mosquitoes. In fact, with the phenomenal growth of rain barrels it should signal a disturbing trend that the mosquito population is set to explode. Mosquitoes love any body of water that remains still long enough for them to release their larvae. Therefore it can only be expected that rain barrels will become a soft target for these pests to multiply. The water collects from your roof via downpipes and is then stored in these water drums to be used at a time that is most probably not regular. This source of water then becomes the best possible breeding ground a mosquito could wish for.
While I've discussed some mosquito control methods before here on GTNI, when it comes to rain barrels there needs to be different solutions - tipping the water out regularly kind of defeats the purpose. So, how can rain barrels and water storage exist without creating a habitat for man's most deadly insect? Easy...here's some gardening tips that should keep them out of your water storage drums forever.
- Add a goldfish - small goldfish love mosquito larvae almost as much as we love chocolate. So why not add one, perhaps two, to each rain barrel. Provided they still have enough air - in other words don't lock off the top of the barrel - keeping a goldfish in your drums should be quite a simple task. The benefit is twofold; 1). the fish will devour the larvae as soon as they are laid reducing your fish feeding bill, and 2). the ammonia excreted from the fish will produce beneficial nitrogen for your soil.
- Produce an oil slick - we all saw how effective the Exxon Valdez spill was at killing wildlife, well the same principle applies here. Providing the water level in your rain barrels can be kept above the output spouts you can pour a layer of oil (preferably food-grade) on top of the water. This acts as a shield for insects getting into your barrels and laying their eggs plus if any eggs do survive they will soon die once they begin to develop into the larvae stage. One important note, don't combine this method of mosquito control with the one above. The oil slick will stop the water being aerated and the fish will eventually die.
- Cover the intake with a filter - if the other two methods seem a little too bizarre for your liking then covering the intake is possibly the next best thing. A pair of nylon pantyhose should do the trick as they are fine enough to stop mosquito infestations but will still allow the water to seep through and collect in the barrels. The downside of this method is that the filter will need to be checked often to ensure that they aren't breaking down or that holes aren't being produced. Even the smallest hole in these can become an access point for mosquitoes and their larvae.
- Chemical larvicides - microbial larvicides are a chemical solution to the problem. If the three options listed above don't seem to deal with your problem, or if you're looking for an easy fix, then larvicides may be your next best option. Granular forms are most likely to be available at your local hardware or garden store and should be added as per the directions at times when mosquito activity is at its peak. As with most chemical solutions it is only a matter of time until mosquitoes build up an immunity to these and they become ineffective or stronger. My advice would be to only use these if you can't find any resolution with the other ideas.
- Mosquito Dunks - these are just a glorified form of larvicide making insertion easier for the user. They perform the same result as the method listed above but are more convenient in their packaging.