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Green news from the UC Division of Agriculture and Natural Resources
by Scott
on March 23, 2014 at 10:02 AM
Great article, but I have a related question:  
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?  
Thanks, Scott
by Andrew Mason Sutherland
on April 3, 2014 at 10:38 AM
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,  
Andrew Sutherland
by Ted
on September 15, 2014 at 5:20 PM
Hi...This is a very informative article...I would just like to ask about the breathing capabilities of the mosquito larvae..How many minutes can they breathe below the water surface before they suffocate?
by joan Keeley
on June 9, 2015 at 3:05 AM
In an entirely balanced pond there is not any have to be compelled to feed the fish as they’ll eat two-winged insect’s larvae, water fleas, worms, plants. Shield pond with EPDM Pond Liners and leave to be troubled concerning damages and issues of pond.
by abdul
on July 5, 2015 at 4:38 AM
Mosquito is a threat to us in Africa, especially during the raining season. It is a disturbing issue here Nigeria. I wish scientist can improve on how to kill mosquito rather than making weapon for killing fellow men. We need to destroy this insect.
by Dillie
on October 5, 2015 at 4:37 PM
i have a small bubble fountain about 18" deep with recirculating water. We don't let it run continually. We now have a lot of Mosquitos. What can we pour in the water to kill in larvae and the Mosquitos flying around it?
Reply by Pamela Kan-Rice
on October 5, 2015 at 4:49 PM
You can use Bacillus thuringiensis (Bt) products such as Mosquito Dunks, Plunks, or Bits, which contain a bacterial agent that kills mosquito larvae but doesn’t affect people, other animals or plants. For more information about mosquitoes, visit
by carlene
on October 27, 2015 at 7:59 PM
I hear just plain cooking oil keeps mosquito from leaving water. oil gets on the wings they can't fly and they die. but I wonder how this would affect fish,i'm thinking not good. but in a still pond i'll bet it will. anything to add,anybody?
by Cheri E
on May 14, 2016 at 6:18 AM
I have been raising mangroves in my home for a while now, and they are getting too big to keep inside on the counter so I wanted to put them outside. However, I was concerned about their bowl becoming a place for mosquitos to breed. What can I put in the water that will keep that from happening but still not harm the mangroves?
by tariq nawaz khattak
on May 14, 2016 at 9:36 AM
Let me share with you one of my finding, which surprised me a lot when one of our student applied along with other plant based extracts from controlling mosquitoes larvae.  
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.
on May 17, 2016 at 12:06 PM
We a inherited a small artificial pond, about ten feet long, two feet wide and two feet deep. Two years ago we placed ordinary "feeder fish" goldfish at 22 cents each, about an inch long. We have no fountain, no nothing, the fish are now over 6 inches long, had babies last year, and no more mosquitoes! We do feed them from april to october (we live on the west coast of Canada). Just be very sure there is no chance your pond could flood releasing fish into the natural waterways - this is would be extremely detrimental to the ecology of local waterways.
by Sophie
on May 19, 2016 at 7:46 AM
Virginia Beach has started its summertime effort to combat mosquito populations throughout the city and this year they are also keeping a close eye on the Zika virus. To avoid mosquito bites, get mosquito nets
by Ali
on May 31, 2016 at 4:25 PM
The old way to remove mosquitoes is to spray or pour a small amount of kerosene into the water. Obviously not where there is fish. This stops the larvae from breathing and the all die within hours. The kero seems to break down quite quickly and disappear. Cooking oil does not disperse over the water in the same way. You will see multicoloured reflections all over the treated areas.
by Jacqueline
on June 7, 2016 at 12:43 PM
Can Mosquito dunks etc. be run through a pump as in a water feature? Any other suggestions? I have birds that often come to bathe and splash in the waterfall and don't want to harm them in any way. Thanks
on July 6, 2016 at 10:10 AM
I have saved rain in several large buckets. Will use in the next couple of weeks. Do I need to add something to prevent mosquito larva ?
by Don mitchel
on August 29, 2016 at 10:16 AM
A thesis written by Elizabeth Kathleen McCraven (University of New Orleans) Electro-Disinfection of Ballast Water, can be found on the web, it states that it is known that mosquito larvae is in ballast water. Her statements on mosquitos and ballast water are written in plain talk that speaks volumes about the way the ballast water is being looked for disease transmissions. Mosquitos feed on algae. New unexplained algae is showing up throughout the Great Lakes. Recent studies have shown large amounts of bacteria ,virus's and algae coming into the Great Lakes after an ocean flush.  
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.
by Joyce Sue
on August 30, 2016 at 9:02 PM
I have a small fountain with recirulating water. I always thought that if there is movement in the water then mosquito's  
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.
by Biswajit rana
on September 1, 2016 at 1:01 AM
i want infortation about the mosquito larva
by Andrew Mason Sutherland
on September 7, 2016 at 10:52 AM
To address comments and concerns above about Bti products ('mosquito dunks'). This microbial insecticide is selective: it only affects fly larvae. It is especially active against mosquitoes, fungus gnats, midges, and other primitive flies. It should not affect adult bees adversely. Once dissolved / suspended in the water, it will circulate freely in pumped systems. Mosquito management should be practiced any time water will be standing for more than five to seven days. Make sure to read product labels to ensure pesticide use is allowed in your state and at your 'site'.
by Lola robuck josey
on September 11, 2016 at 8:10 AM
I read that coffee grounds were effective in destroying mosquito larvae. True?
by Andrew Mason Sutherland
on September 13, 2016 at 10:25 AM
To Lola robuck josey,  
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.
by Philip
on November 26, 2016 at 3:37 PM
Adding to what Lorrine has already said. A few small fish are the answer and goldfish will add interest and colour
by steven Charles
on April 23, 2017 at 11:52 AM
does putting 6 or 8...drops of olive oil into water barrel stop the creation,life of larvae, mosquito living..?  
Thank You
by Andrew Sutherland
on April 24, 2017 at 10:33 AM
RE: question posed by steven Charles: Some insecticidal oils are used by professionals and government agencies in large water bodies to prevent mosquito larvae from breathing at the surface, thereby killing them. I don't think these oils are labeled for general use by the residential public, however. I suggest you contact your county's Mosquito and Vector Control agency to learn about approaches in your area ( They often provide free mosquitofish for use in containers or ponds.
by Michelle
on May 16, 2017 at 12:26 AM
We have a cistern system that collects water into a deep well-like structure. This is the first year that we live here and I am concerned about mosquitoes. Will this be a breeding ground for larvae or do they not breed in deep water with steep sides as mentioned in your article? Could I keep goldfish in a structure like this? I am afraid of decomposing fish or using toxic products as we use the water to irrigate our garden. Is BTI considered organic?
by Monica Bhardwaj
on July 31, 2017 at 1:08 PM
By Eng. Monica Bhardwaj  
what's the name of fish which used in water for killed mosquitoes????
by Salman
on August 11, 2017 at 10:46 PM
After trying almost all ideas i came up with a conclusion that the best way to kill mosquito larvae is to keep fish and periodically change of water. It is better to keep guppy fish or cichlid fish and make drain in your ponds or water garden. Change water time to time. Sunlight also helps to avoid mosquito growth. Do not put any kind of oil because it will do nothing but create a mess.
by Victoria Kretschmer
on November 1, 2017 at 8:54 AM
I live in cape Town South Africa. We are experiencing the worst drought ever and are restricted to 87 litres of water per person per day. I have sadly had to switch off my pool pump and am using the algae water to flush toilets and water plants so they don't die, which is why I cant add chlorine. Now I have a breeding pond for a huge amount of mosquitos. What can I add to ONLY kill the larvae and not other insects or birds. I am desperate as I need the water and don't want to empty the very large pool, which could also damage the pool lining if empty
by Patti Allen
on June 24, 2018 at 10:50 AM
I used the Dunks in my circulating fountain. Unfortunately, the Dunks broke up into little pieces which clogged my pump.  
I would like a liquid option that kills the mosquito larvae but not any other wildlife.  
Would like a suggestion of another product.  
Thank you
on July 12, 2018 at 6:36 AM
Mosquitoes, especially in the tropical countries can cause sickness like dengue, so one really has to be considerate about how clean their ponds are for the safety of others. This is a very informative article and I think the most important thing is just regular cleaning and additional help from larvicides.
by Daniel Fischer
on July 22, 2018 at 7:30 PM
Live on a high bank (25 ft) above a small river that floods periodically and leaves a meander with water maybe 100 yards long and 30 yards wide. It eventually dries but breeds mosquitoes. Any oil that may be safe for other wildlife?? Offer human beings to? Or another idea??
by Barbara
on March 15, 2019 at 6:16 PM
I want to use Mosquito Dunks for my rain barrel water. Will this contaminate the water making it unusable in the yard and garden
by Shaylee Packer
on November 20, 2019 at 6:00 AM
That is interesting that the mosquito larvae prefer shallow water over deeper water. My parents have a small pond in their backyard, I will have to go check it out and make sure that it is over 24 inches deep, even on the edges. If this works, they will be so grateful, they have had such an issue lately.
by k j
on February 29, 2020 at 3:33 PM
can water treated with soap, vinegar, oil or dunks to kill mosquitos be safely used to water my garden
by Cynthia
on April 25, 2020 at 3:53 PM
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 ?  
Thank you
by wendy winter
on May 5, 2020 at 12:59 PM
could I add vinegar or epsom salt to a pond to keep mosquitoes out? If birds drink from the pond would that harm them?
by Sara l Hamilton
on June 8, 2020 at 12:12 PM
I have a pool that is 6 foot round and 3 foot deep. Could I use lavender oil in the water to stop mosquitoes.
by Arthur John Haecker, III,
on July 8, 2020 at 12:03 PM
Our pool is seldom used and has a layer of oak leaves on the bottom which darkens the water. The local health department assumes the pool was stagnant and posed a mosquito threat and threatened legal action. My son immediately dumped 20 lbs of chlorine in the pool which killed all life including the frogs which ate the larva. Will that chlorine kill the Bacillus thuringiensis?
by Andrew Mason Sutherland
on July 9, 2020 at 11:48 AM
To address recent (2020) questions above:  
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.
by Dee levenson
on July 26, 2020 at 1:56 PM
Is the water that the mosquito dunks are in safe for humans? We have a 15 gallon fountain in our yard. I’ve always used the dunks to control mosquito larvae. But now our toddler keeps playing in the water and licking her hands. Do I need to be concerned or is it such a small amount I don’t need to worry too much? Where the fountain is located, it’s impossible to block off or keep her out of it
by Leon
on September 17, 2020 at 6:42 AM
Hi, I have a fountain that heavily drips water in a 1-foot diameter pattern into a 4-foot diameter pool. It runs full time, and the pool averages about 1-foot deep. I have a big mosquito problem and wondering if they're breeding in the water, or even perhaps in the moist soil around the fountain from water that "bounces" out. My understanding is that the water needs to be "stagnant" for mosquitoes to breed, but how stagnant? And I've now read some mosquitoes breed in moist soil instead of standing water? Thank you!
by May Gan
on January 27, 2021 at 6:27 AM
Great, educational article, thank you!  
May in Malaysia
on April 17, 2021 at 2:06 PM
Can BTi be used in a cistern? the water goes through 3 filters and an ultraviolet system. We have screens over the overflow, but when the cistern hatches are opened, a lot of mosquitoes come out
by Henry Killingsworth
on May 28, 2021 at 11:23 AM
I appreciate you helping me to understand how to control mosquito populations. I am wanting to get a standing water fountain for my yard. Keeping these tips in mind will help me prevent my yard from getting swarmed by mosquitoes.
by James Kvcala
on July 2, 2021 at 7:01 AM
We live in Georgia, where my wife was allowing rainwater to accumulate in a small bathtub on our back porch for irrigation use. Tree frogs laid eggs and tadpoles hatched out in profusion. There was a little green algae in the tub and my wife augmented the tadpoles’ diet with a tiny bit of dry cat food. All seemed well. Seeing mosquito larvae in the water, she added a mosquito dunk. The next day all the tadpoles were dead. Not scientific, but hard to see what else could account for their sudden death.
by Pan Wilson
on July 17, 2021 at 1:52 PM
I'm reading everything carefully and do notice conflicting information. The BTI sounds promising but I have continued concern about tadpoles. Grey Treefrogs have hatched out in my rain barrels and the tads' are the same size as the mosquito larvae. I want to remove only the mosquitos. Fish seem to eat everything and I worry about the tad's breathing if I use oil or vinegar. Is there a final word on this?
by Tasriful islam
on August 17, 2021 at 10:57 PM
Great article, but I have a related question:  
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 ?  
Thank you
by TL
on February 15, 2022 at 7:01 AM
Is it safe to put both a mosquito tablet and a Chlorox tablet in the water in my rain barrel each month? Safe for the plastic barrel? Safe to use the water to water the grass? Safe in that there are no harmful gases to breathe? Thank you.
by Davis
on February 27, 2022 at 9:39 PM
Hi, I have a water feature incorporating a small waterfall located in our living. So the water is not entirely stagnant but constantly waving, if you know what I mean. The dripping of water gives off a very good therapeutic effect. However I hv to turn off the pump every night when I sleep as the tinkering sound will wake me up. I’m a very light sleeper. However the pump will run again the next morning. I would say 12 hrs moving and 12 hrs rest. You reckon the larvae can survive in such set up?
by met solar
on March 11, 2022 at 4:34 AM
Great article,
by Kristin
on July 2, 2022 at 1:05 PM
I have the same comments and questions as Davis. I have a shallow bird bath bowl with a solar fountain that runs about 6 hours a day. Is that sufficient to prevent mosquito infestation?
by Amal Raj
on April 17, 2023 at 12:16 AM
Mosquito net is the best option. As far as I know this is not only a safe way but also an effective way. Better than many harmful repellents. We being a mosquito net company, has seen the rise of net fixing.
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