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How to Use Mosquito Dunks: Controlling Infestations with a Mosquito Trap

mosquito dunk floating in homemade mosquito trap

Mosquito Dunks are a popular and effective means for controlling mosquito larvae in standing water. These tablets or “dunks” contain a bacterium called Bacillus thuringiensis israelensis (Bti), which is toxic to mosquito larvae but harmless to humans, pets, birds, and aquatic life.

Although dunks may look like a pesticide, they are not! Bti is a naturally occurring bacteria, making this a nice natural solution for major mosquito problems.

It’s best to prevent mosquito infestations from the start when you can. For a complete guide to assessing, handling, and hopefully preventing a range of mosquito problems, first read our complete guide to getting rid of mosquitoes.

Once you’ve decided that a mosquito trap for mosquito larvae is the right path for you, read on to learn how to use mosquito dunks (and related tools).

How to Use Mosquito Dunks Properly

  1. Identify the Problem Areas: Look for areas with standing water, where mosquitoes are likely to lay their eggs. This can include bird baths, ponds, water gardens, rain barrels, rain gutters, and unused swimming pools. Here’s our guide to locating the parts of your home where mosquitos are likely to lay eggs.
    • Of course, it’s best to prevent mosquito infestations from the start, when you can. See our complete article on mosquito prevention for more tips.
  2. Read the Label: Before using Mosquito Dunks, it’s important to read the manufacturer’s instructions for any specific recommendations or precautions.
  3. Calculate Water Volume: Estimate the volume of standing water in the area you wish to treat. This will help you determine how many dunks you need. Generally, one Mosquito Dunk is effective in treating up to 100 square feet of surface water (about the size of one car parking space!) for up to 30 days. However, your product may differ: be sure to refer to the product label for instructions for your edition of a dunk.
  4. Break the Dunks if Needed: If you are treating a small area, you might not need a whole dunk. Mosquito Dunks can often be broken into smaller pieces for treating smaller volumes of water.
  5. Place the Dunks in Water: Simply place the appropriate number of dunks or pieces into the standing water. The dunks will float and slowly release the Bti bacteria over time.
  6. Monitor and Reapply: Pay attention to the treated area, and if you notice mosquito activity starting to pick back up, or if heavy rain has likely diluted the treatment, it might be time to add a new dunk. Normally, one dunk will last about 30 days.
  7. Store Properly: Keep unused Mosquito Dunks in a cool, dry place, out of reach of children and pets.

Remember, while Mosquito Dunks are very effective at controlling mosquito larvae, they won’t do anything for adult mosquitoes.

It’s always good to complement their use with other mosquito control measures, which may include reducing breeding sites, using mosquito traps, growing plants mosquitos avoid, and employing personal protective measures like mosquito repellent.

How to Make a Mosquito Trap

If you have a larger property and are having a hard time identifying where mosquitoes come from, you may want to create a homemade trap and place it in a problem area outside.

mosquito trap resting in the shade near a tree

home-made mosquito trap with sticks and grass in a bucket

To make such a trap, you’ll need at least one bucket and one dunk.

  1. Fill bucket(s) with water, dirt, and grass
    • As we’ve noted in our article about where mosquitoes lay eggs, mosquito eggs and larvae require plenty of water, but don’t want to risk having their eggs carried away by a current. Thus, they’re attracted to stagnant water. Placing dirt and grass in the bucket produces “old water” chemical reactions for them to sense.
  2. Place bucket(s) in shade
    • While mosquitoes love warm, humid environments, there is a such thing as “too hot” for the eggs and larvae. Shade will make the bucket a more attractive breeding ground for female mosquitoes, and reduces risk of damage to the Bti bacteria.
    • If you are covering a large area, place the buckets 50 feet apart from one another. Each bucket should be able to cover approximately a 50-foot radius.
  3. Add a dunk to the bucket(s).
  4. Wait!

How do mosquito dunks work?

Mosquito Dunks work by releasing a specific strain of bacteria called Bacillus thuringiensis israelensis, often abbreviated as Bti, into the water. This bacterium is naturally occurring and is harmful only to mosquito larvae and a few other closely related insects, such as black flies. It is safe for humans, animals, fish, and other non-target organisms.

Here is how the process works:

  1. Release of Bti: When a Mosquito Dunk is placed in standing water, it slowly dissolves and releases the Bti bacteria into the water.
  2. Consumption by Larvae: Mosquito larvae feed on microorganisms in the water. As they consume the Bti bacteria, it is ingested into their digestive systems.
  3. Production of Toxins: Once inside the larvae’s digestive system, the Bti produces toxins that are specifically effective against the larvae. These toxins attack the lining of the larvae’s gut.
  4. Death of Larvae: The toxins cause the larvae to stop eating, and their digestive systems are severely damaged, which leads to their death. This usually happens within a few hours to a couple of days.
  5. Prevention of Adult Mosquitoes: By killing the larvae before they can mature into adult mosquitoes, the Mosquito Dunks effectively reduce the population of mosquitoes in the treated area.

It’s important to note that Bti is highly specific to mosquito larvae and a few other similar insects, and it does not harm other wildlife or humans. This makes Mosquito Dunks an environmentally friendly option for controlling mosquito populations.

Frequently asked questions

Where can I find a Mosquito Dunk?

The most popular version of mosquito dunks comes from Summit. This six-pack is ideal for creating long-lasting mosquito traps and potentially servicing multiple points of pooled water in your yard.

Summit...responsible solutions 110-12 Mosquito...

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However, while those dunks have the advantage of lasting for a long time, they can take up to 48 hours to work.

If you want a faster kill and more flexibility in implementation, consider Mosquito Bits, also from Summit. In this version of the product, Summit coats corn cob granules in BTI. These granules will complete their initial kill in less than 24 hours. They also have the advantage of being easy to mix into planters or other locations where not enough water is present for the dunks to float. They last for less time, though, remaining effective for only 14 days at the high end.

Mosquito Summit Dunks for Insects (6 Dunks) (1, 30...

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How long does it take for a Mosquito Dunk to work?

A mosquito dunk can be expected to complete its first larvae kill in 48 hours. Each whole dunk set in water will last for 30 days.

If you need a faster solution, Mosquito Bits can complete a quick kill in just 24 hours. However, the bits remain effective for less time – up to 14 days total in the best-case scenario.

Will a Mosquito Dunk kill any other bugs?

Yes! While Bti is not effective against all pests, fungus gnats are a prime example of another insect harmed by the Bti in dunks.

Again, a reminder that Bti is effective at interrupting the reproductive cycle of these bugs. It will not kill adults mosquitos, gnats, or other bugs, but it will prevent new pests from surviving.

Are mosquito dunks safe for plants?


How to use mosquito dunks in potted plants

While mosquito dunks could be used in potted plants, it’s likely better to use mosquito bits for potted plants, as they’re easy to mix into the potting soil. If dunks are what you have, though, you can break the dunks into smaller pieces.

Are mosquito dunks safe for dogs?

Yes! Dogs, cats, as well as other common pets won’t be in any way affected by mosquito dunks, even if consumed directly. In fact, they’ll be a light dose of protein and calcium!