A mosquito dunk is a solid, donut-shaped larvicide designed to float on standing water. It utilizes a natural agent to interrupt the mosquito life cycle, preventing the insects from reaching the adult, biting stage. The simple and definitive answer to whether this product attracts adult mosquitoes is no, they do not.
Answering the Attraction Question
Adult female mosquitoes, which are the ones that bite, locate their hosts by detecting cues like carbon dioxide, body heat, and specific odors. The dunks contain no such compounds; they are inert masses that slowly release a biological agent into the water. Female mosquitoes select standing water for egg-laying based on natural water characteristics and chemical cues from decaying organic material, not the dunk itself. Since the dunks do not emit scents or pheromones relevant to adult mosquito behavior, they do not lure adult insects toward the treated area.
How Mosquito Dunks Eliminate Larvae
Mosquito dunks utilize a naturally occurring soil bacterium known as Bacillus thuringiensis israelensis, commonly abbreviated as Bti. This bacterium is the active ingredient and is specifically toxic to the larvae of mosquitoes, black flies, and some midges. When a dunk is placed in standing water, it gradually releases the Bti spores and protein crystals. The mosquito larvae, which are constantly feeding on organic matter, ingest these spores and crystals.
Mechanism of Action
In the highly alkaline environment of the mosquito larval gut, the ingested protein crystals become activated and dissolve. The activated toxin then binds to specific receptor cells in the larval gut lining, causing the cells to rupture and paralyze the digestive system. The larva immediately stops feeding and typically dies within 24 to 48 hours of ingestion. Bti is highly specific and harmless to mammals, birds, fish, and other non-target insects because the toxin is only activated in the alkaline conditions of the mosquito larval gut.
Proper Application and Usage
Mosquito dunks are intended for use in any standing water source that cannot be easily drained and holds water for longer than seven days. Common breeding sites include:
- Decorative water gardens
- Bird baths
- Rain barrels
- Unused swimming pool covers
- Clogged rain gutters
- Old automobile tires
The standard dosage is generally one full dunk for every 100 square feet of water surface area, regardless of the depth. For smaller containers, the dunk can be broken into smaller portions. A quarter or half of a dunk is often sufficient to treat water containers with a surface area between 1 and 25 square feet. If a water container is temporary or prone to drying out, the mosquito dunk remains effective once the water returns. To prevent the dunk from floating away in a larger body of water, it can be anchored using a string tied through its center hole.