What are Mosquito Dunks and How to Use Them

picture of red mosquito dunk product

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

Sarah bahr
Sarah Bahr

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.

Sarah Bahr


Where to Use Mosquito Dunks 

image of a rain barrel
Photo Credit: schulzie / Canva Pro / License

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:

  1. 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.

  1. 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.
  2. 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.

  1. 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

stagnant water in trays
Photo Credit: ThamKC / Canva Pro / License

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

mosquito repellent
Photo Credit: pixelshot / Canva Pro / License

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

Can You Use Mosquito Dunks Around Pets?

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.

Do Mosquito Dunks Control Fungus Gnats?

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.

What is The Difference Between Mosquito Dunks And Mosquito Bits?

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.

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

EPA – Skin-Applied Repellent Ingredients

Main Image Credit: Mike Mozart / Flickr / CC BY 2.0

Raven Wisdom

Raven Wisdom is a writer with a passion for pest control, gardening, sustainable living, and making a positive impact in the world. When she's not defending her garden from critters in the wilds of West Texas, Raven can be found writing, wrangling two kids in a neurodivergent family, and supporting her local animal rescues.