
Mosquitoes are not just a nuisance; they can also harm people and pets. Infected mosquitoes can transmit mosquito-borne diseases, including the West Nile virus and Zika virus. One effective way to combat these diseases is by using mosquito dunks. But what are mosquito dunks, and how do you use them?
If you’re interested in how to use mosquito dunks in rain barrels, check out our personal experience below.
What are Mosquito Dunks?
Mosquito dunks work as an easy and effective microbial larvicide designed to control mosquito populations in residential, commercial, and park settings. They are safe, eco-friendly, and protect against mosquito-borne illnesses, ensuring the safety of people and pets.
How Mosquito Dunks Work
Mosquito dunks contain a naturally occurring bacterium called Bacillus thuringiensis israelensis (Bti) as the active ingredient. This bacterium specifically targets mosquito larvae (the second life stage).
When mosquito dunks are placed in standing water, the bacteria produce a toxin that destroys the gut lining of the larvae, effectively killing them within a few days.
Bti larvicides go by many names depending on their shape or form:
- Mosquito dunks (disc-shaped products sometimes called mosquito donuts or tablets)
- Mosquito bits (these are in granular form)
- Mosquito dunk chunks (these are in small chunks, as the name suggests)
Where and How to Use Mosquito Dunks
Mosquito dunks are helpful in areas with standing water, especially where mosquitoes breed, such as bird baths, fountains, and rain barrels. Larvicide should only be applied to areas where standing water cannot be eliminated. It works as a preventative treatment or when larvae are already present.
Firsthand Experience: How Bt Keeps my Rain Barrels Mosquito-Free

In summertime, rain barrels are quite a cost savings if you have a garden. Rainwater is free, and a few home-built rain barrels are an inexpensive investment that can last for many summers to come.
But how do you prevent these cost-saving barrels from becoming a mosquito breeding ground? Bt. This naturally occurring bacterium is inexpensive, safe, and prevents larvae from developing should any mosquitoes lay eggs in your barrel.
For my barrels, I invest in a pack of 20, which costs about $20, and keeps several rain barrels skeeter-free all summer long. Make a note in your phone calendar to replace them once per month. It’s the best $20 I spent all summer.
Where to Use Mosquito Dunks

Bti products can be used in various standing water sources around your home or property. Placing mosquito dunks in these areas can eliminate mosquito larvae.
- Birdbaths
- Rain barrels
- Gutters
- Flowerpots
- Pool covers
- Untreated swimming pools or unfiltered water
- Other sources of stagnant water
Do Not Use Mosquito Dunks in These Places:
- Where runoff flows into natural water bodies, such as streams or into storm drains
- Moving water — mosquitoes are unable to reproduce in moving water
- In natural bodies of water like lakes or wetlands
- Rain gardens
How to Use Mosquito Dunks
Dunks treat standing water that cannot be quickly drained. One donut can treat up to 100 sq. ft. of surface water and kill mosquito larvae within hours. Results can be seen in 48 hours, and the treatment remains effective for 30 days.
Follow these steps to prevent mosquito larvae from developing into adults:
- Inspect your property for areas where water may accumulate after rain. Mosquitoes like Aedes albopictus, a mosquito responsible for transmitting Zika, lay their eggs in these areas.
Note: Mosquito larvae need only a bottle cap of water to survive.
- Prevent standing water by emptying and turning over buckets, unused flower pots, canoes, and wheelbarrows. Clean your gutters so water flows freely through them, and place lids on outdoor trash cans.
- Add the appropriate amount of product into the water and wait. Keep it in place with the string hole in the middle, or let it float freely. The product dissolves slowly, releasing bacteria that prevent mosquito larvae from growing.
Safety tip: Wear gloves or wash your hands after handling the tablets, as they may cause mild skin irritation. Avoid getting any materials in your eyes.
- For smaller areas with less than 100 square feet of surface water, break the tablet and follow the instructions on the label.
Pros and Cons of Using Mosquito Dunks
Mosquito dunks are a practical way to get rid of mosquito larvae and prevent them from becoming adult mosquitoes that can irritate and spread disease.
Pros of Using Mosquito Dunks
- Effective at controlling mosquito larvae
- Safe for humans, pets, and wildlife
- Easy to use and apply
- They can be used in a variety of standing water sources
- Environmentally friendly compared to other chemical mosquito control methods
Cons of Using Mosquito Dunks
- Only kill mosquito larvae and are not effective against adult mosquitoes
- They must be replaced every 30 days or as needed
- When covering a large area, multiple dunks may be necessary
- Less effective in areas with high mosquito populations and many breeding sites
Other Ways to Get Rid of Mosquitoes
Using an Integrated Pest Management approach can reduce the risk of mosquito-borne diseases and keep yourself and your loved ones safe. Here are a few tips on how to get rid of mosquitoes around your home.
Eliminate Standing Water

Remember, mosquitoes need only a capful of water to lay eggs, so be thorough in eliminating potential breeding sites. Here are some steps you can take to prevent mosquitoes from breeding:
- Fill low spots or improve drainage in the yard to prevent puddles from forming.
- Tightly cover water storage containers such as buckets, cisterns, and rain barrels.
- Secure septic tank covers, repair any cracks, and cover ventilation pipes with fine mesh.
- Drill holes in the bottom of tire swings, trash cans, and recycling bins to allow water to drain.
- Change or empty water in pet dishes, bird baths, animal watering troughs, etc., at least once a week.
- Keep roof gutters clean to prevent water from pooling.
- Clear away debris or contract a junk removal service to prevent the buildup of decaying material and related items.
- Treat unfiltered swimming pools with larvicide. For fish habitats like koi ponds, consider adding a few mosquitofish.
Install Mosquito Barriers
To stop mosquitoes from biting you while indoors, you need barriers that can stop them. Here are some examples:
- Put screens on windows and doors if there are none.
- Cover any holes or gaps in walls, doors, and windows to keep mosquitoes out.
- Ensure windows and door screens are tight enough to keep bugs out.
- Cover beds, strollers, and baby cribs with mosquito nets.
Use Mosquito Repellents

Use safe and effective mosquito repellents registered with the EPA to avoid mosquito bites. Check that the repellent contains one of the active ingredients listed below. These repellents are safe for everyone, including pregnant and breastfeeding women, if used as directed on the label.
- Oil of lemon eucalyptus (OLE), often used in natural mosquito repellents
- DEET
- Para-menthane-diol (PMD)
- Picaridin (also known as KBR 3023 and icaridin outside the US)
- 2-undecanoate
- IR3535
Note: The EPA provides a search tool to help you find the right insect repellent for your needs.
Treat Your Yard
To prevent mosquito-borne diseases caused by adult mosquitoes, you can have a professional mosquito control company spray your lawn with adulticides, which are insecticides that kill adult mosquitoes. Experts can tell you which adulticide to use depending on the type of mosquito, pesticide resistance, and weather conditions.
FAQ: About Mosquito Dunks
Yes, Mosquito dunks are safe for pets and wildlife, as the active ingredient Bacillus thuringiensis israelensis (Bti) is non-toxic to them even if they eat one of the tablets.
Yes, mosquito dunks are an effective control measure for fungus gnats and their pupae. To manage fungus gnats, soak a tablet in water overnight, remove it, and use the water to water your plants. The tablet is reusable, making it a budget-friendly solution.
Mosquito dunks And mosquito bits contain the same active ingredient, Bti, but they differ in form and application. Dunks are donut-shaped and are more suitable for larger areas, while bits, which are in granular form, are better for smaller areas. Both dunks and bits are safe for humans, pets, and wildlife, and they effectively control mosquitoes.
Conclusion
Overall, using mosquito dunks is a safe, practical, and environmentally friendly way to control mosquito populations and reduce the risk of mosquito-borne diseases. By incorporating mosquito dunks into your mosquito control plan, you can help protect yourself, your family, and your community from the health risks of mosquitoes.
If you’d rather leave the war against mosquitoes in someone else’s hands, contact Pest Gnome to connect you to the best pest control experts in your area.
Sources:
New York State Health Department – Using Mosquito Dunks
Montgomery County Maryland Pest Management – Chemicals & Other Techniques
Center for Disease Control – What You Need to Know about Bti
Audubon Society of Northern Virginia – How to Set Up a Mosquito Larva Trap
Mississippi State Department of Health – Mosquito Prevention: What the Homeowner Can Do
Mamaroneck Village New York – Mosquito Dunks – Frequently Asked Questions
Main Image Credit: Mike Mozart / Flickr / CC BY 2.0