It's the first nice day of the season. You're sitting down for a meal outside with the family.

Suddenly that annoying buzzing around your ears. Then, a pin prick. Your hand swats wildly *SMACK*, but nope. The skeeter beat you. You look down and there it is: a giant, red, itchy welt.

The fresh joy of being outside basking in the Spring sun just became tainted. It's mosquito season.

There´s something else this incident informs you about.

You are too late.

Late with taking precautions. Preparing your yard to reduce mosquito infestation.

Founding Father Benjamin Franklin already said it, "An ounce of prevention is worth a pound of cure."

Which certainly goes for those vicious bloodsucking gits.

You have heard about Mosquito Bits and Dunks before. While scratching your welt you wonder,

Do they work?

This is a legit question. If you have a really large yard you will be spending about 30 bucks a month so it better be worth it and work. Of course, for medium or small sized yards costs are much lower.

Does this larvicide really have to ability to kill mosquito larvae?

To keep it plain and simple, yes, Bits and Dunks really work.

EPA has this to say:

"Killing mosquito larvae with microbial larvicides before they emerge as adults can reduce or eliminate the need for ground or aerial application of pesticides to kill adult mosquitoes.

It should be noted that how long and well they work depends mainly on "the mosquito species, the environmental conditions, the formulation of the product, and water quality".

What exactly are mosquito dunks and bits?

Mosquito Dunks and Mosquito Bits are made from naturally occurring soil bacteria called Bacillus thuringiensis strain israelensis (for the rest of us: Bti).

They are one of the most effective products on the market today.

You may be familiar with Bt products as a common form of pest control originating in the early 1900s. Bt biocontrol products are often used on agricultural and garden pests, such as

Btk on caterpillars and

Btt on beetles.

Bti is simply a different strain of Bt that only affects mosquitoes and black flies. (it's very specific in its larvicidal activity)

Since Bti occurs naturally in the environment, it is considered an all-natural biological control product. Dunks and bits are produced by harvesting Bti from soil, then inactivating the bacteria with enzymes.

The inactivated bacteria is added to fillers and packed neatly into dry briquettes or pellets. By the time it is sold to the consumer, it is no longer a living bacteria, however it is still just as effective in killing mosquito larvae.

How do they work?

When eaten by a mosquito larvae, "toxic crystals" form which travel to the stomach and enter the stomach cells. The crystals cause the stomach cells to explode, forcing the mosquito larva to stop feeding until it starves to death.

It can take several days for all of the mosquito larvae to die, so if you see no immediate results, don't be alarmed.

Don't fret if there still appear mosquitoes upon treatment

Older mosquito larvae tend to stop eating as they approach the next life stage, therefore Bti may not be as effective on older larvae and some adult mosquitoes may emerge after the initial Bti treatment.

Bti vs Bs – Bacillus thuringiensis israelensis vs Bacillus sphaericus

A similar product to Bti is Bacillus sphaericus (Bs) which is another bacterial biological control product.

The difference between Bti and Bs is that Bti products contain dead bacteria, whereas Bs products contain live bacteria.

Bs downsides:

Bs may not be as effective on certain species of mosquitoes.

Another disadvantage, there has been some recent concern about Bs insecticide resistance in populations of disease-carrying mosquitoes.

Studies indicate it appears to be less effective in killing the Aedes species

Most mosquito control products purchased by homeowners contain Bti, however Bs is an additional mosquito control option.

Dunks vs. Bits, when to use which?

Bti products come in several formulations, including donuts and briquettes (collectively known as dunks), and granules or pellets (bits).

Main difference:

Dunks last longer. They dissolve slowly and have a time-release feature.


They dissolve slowly and have a time-release feature. Bits work more work quickly. Need to be applied more often but offer quick results.


Mosquito Dunks

Dunks