Mosquito management for ponds, fountains and water gardens
Mosquitoes can be managed using an integrated approach that relies mostly on prevention, using biological and chemical controls when necessary. The key strategy is to eliminate all potential breeding sites; even one ounce of standing water can support a population of larvae. What can be done, however, when an outdoor space contains a water element? Here are a few tips.
Water features in the landscape will invariably attract adult mosquitoes, but attempting to control them or prevent their egg laying is difficult. Larvae are easier to manage, since they are concentrated in known areas, don't yet bite, and can't fly away. Larvae prefer shallow water that is less than 24 inches deep, so install water features that are deeper than 2 feet. Ponds or features that provide a steep slope or have vertical walls that quickly drop off into deep water will also be less favorable to mosquitoes. Adding a fountain, waterfall, or other device increases water circulation and reduces the stagnation that allows mosquitoes to breed.
Remove excess vegetation and organic debris that provide mosquito larvae with food, shelter from the sun, and hiding places from predators.
In natural environments, bacteria, nematodes, other insects, crustaceans, and fish often keep numbers of mosquito larvae low. Conserve predators such as dragonflies and backswimmers, which may have colonized ponds, by avoiding broad-spectrum insecticides and consider introducing fish. County vector control services may provide free mosquito fish, voracious consumers of mosquito larvae and pupae. Never release mosquito fish into natural water bodies, since these fish aren't native to California and can disrupt ecosystems.
Although these measures will prevent problems in most cases, mosquito larvae may still develop in some ponds.
In gardens with lots of plants growing in still water, it may be impossible to keep mosquitoes from breeding. Regularly check water features for larvae, which periodically come to the surface to breathe through abdominal siphons Watch for the larvae's characteristic wriggling movement, or use fine dip nets to monitor for larvae. It is important to act quickly to kill mosquitoes when they are small, easiest to manage, and before they become adults and start biting.
Larvicides containing spores or metabolites of the bacterium Bacillus thuringiensis israelensis (Bti) (e.g., Mosquito Dunks, Mosquito Bits, Microbe-Lift, and other products) act as stomach poisons when ingested, killing larvae within a few days. Bti affects only fly larvae, so it won't harm predatory insects living in the pond or water feature. Another effective larvicide is the insect growth regulator (IGR) methoprene (e.g., Pre-strike Torpedos). IGRs interfere with larval molting and also take a few days to kill, but they have a broader spectrum of activity, affecting most juvenile insects and other arthropods that might be in the pond. Both Bti and methoprene are available as granules or pellets, remain effective for about a month, and as with all pesticides, should be used only according to label directions.
For more information about mosquitoes, visit http://www.ipm.ucdavis.edu/PMG/PESTNOTES/mosquitoes.html.
This article by Andrew Sutherland, UCCE advisor in the San Francisco Bay Area and UC Statewide IPM Program, was originally published in the June 2013 issue of the Retail Nursery and Garden Center IPM News. Read the entire article at http://www.ipm.ucdavis.edu/RETAIL/retail-newsletter.html
The 'donuts' you reference were most likely 'mosquito dunks', containing an active ingredient derived from a naturally-occurring soil bacterium, Bacillus thuringiensis israelensis (Bti). The metabolites from these bacteria are toxic to insects once ingested; they should have no effect on vertebrates such as tadpoles. Perhaps something else happened to kill your tadpoles. Look carefully at the product label next time you try this to make sure Bti is the only active ingredient and that you apply the correct amount. You may also consider mosquitofish as predators, available from your county's Vector Control program. Best regards,
It is an organic compounds and not toxic for fish.It kills mosquito larvae within one hour with 0.125 ppm concentration.In fact its a great finding and I want to go commercial on it.
Dr Tariq Pakistan.
Without federal ballast water protection for ships exclusively using all the different Great Lakes, each with their distinctively different echo systems and problems. What new disease's such as Zika will the mosquitos species in the Great Lakes prove to carry? Florida is rampant with algae mosquitos feed on algae.
could not survive..well, just found black mosquito larvae along with little red worms in there. I am hesitant to use the "dunk" because my next door neighbor has bee hives and I do not want to harm the bees. The dunk claims it is safe for animals, fish and birds but nothing about bees. I have yet to year from the company. Please advise if dunks are bee safe. Thank you.
I have never heard of using coffee grounds to 'destroy' mosquito larvae. I believe the main effects of such an application would be to acidify and reduce clarity of the water. This sounds like a terrible idea.
what's the name of fish which used in water for killed mosquitoes????
I would like a liquid option that kills the mosquito larvae but not any other wildlife.
Would like a suggestion of another product.
In this quarantine I decided to grow waterlillys. I used a bucket to see if the would actually grow, and to my surprise it did. It still very small and the bucket is not big either. These dunks seem to be to big for the space. How do I know how much to introduce to my bucket ?
Vinegar, soap, and epsom salts are not registered nor recognized as mosquito control products and should not be used for this purpose. Some oils are effective against mosquito larvae since they form a physical barrier at the surface that prevents larvae from "breathing". With this said, only specific oil products have been tested against mosquitoes and registered as pesticides by the EPA; other oils, especially household oils or plant-based essential oils, should not be used and may have deleterious effects on plants growing in ponds and water gardens. Mosquito Dunks (or Mosquito Bits for smaller water volumes, such as the bucket referenced by Cynthia above) are registered Bti bio-insecticides for residential homes and gardens. Water treated with Bti should not pose hazard to vertebrate animals (such as birds) or to plants. Most Bti products contain live bacterial spores that may be killed by disinfectants (such as the chlorine treatment mentioned by Arthur above).
I'm so glad this article continues to be so popular! Keep the questions coming.
May in Malaysia
We love the tadpoles that appear at the same time as the unwanted mosquito larva. Last year we tried the donuts to kill the mosquitos however they also killed the tadpoles.How do I know how much to introduce to my bucket ?
We love the tadpoles that appear at the same time as the unwanted mosquito larva. Last year we tried the donuts to kill the mosquitos however they also killed the tadpoles. To your knowledge, what is the best way to kill the larva and keep the tadpoles?
Posted by Scott on March 23, 2014 at 10:02 AM