Living near one of the Highland Lakes means mosquitoes are not a temporary nuisance. They breed in standing water, and lake edges, low-lying lots, and the slow-moving inlets around the lakes give them plenty of it. Mosquito dunks are a real product with a real mechanism, and a lot of homeowners reach for them first. The question is what they can and cannot do, and when the jump to professional service makes sense.
Quick answer
Mosquito dunks contain Bti, a bacterium that kills mosquito larvae in standing water. They work for what they target, but adult mosquitoes travel from a wide area and breeding happens in tiny amounts of standing water that dunks cannot all reach. Professional treatments use barrier spray plus source reduction to knock down active adults and interrupt breeding on a schedule.
Dealing with this right now?
Mosquitoes making your Highland Lakes backyard unusable? ACI Pest & Lawn provides scheduled barrier treatments across Kingsland, Marble Falls, and the surrounding area. Schedule a service and we will address the adults and the breeding sites at the same time.
See how we handle it on our mosquitoes page.
How Mosquito Dunks Work
Mosquito dunks contain Bacillus thuringiensis israelensis (Bti), a naturally occurring soil bacterium. Mosquito larvae that ingest it die before reaching adulthood. The dunks are placed in standing water, dissolve slowly, and remain effective for roughly 30 days. They are safe for fish, birds, pets, and people, and the EPA has approved them for use in livestock water troughs and bird baths as well as ornamental ponds.
The limitation is scope. Dunks can only treat water where you place them. They do nothing to adult mosquitoes, they do not treat the vegetation where adults rest during the day, and they do not reach the small, hidden water sources (a bottle cap of water, a clogged gutter, a tarp fold) that account for a significant portion of breeding.
Where the Dunks Fall Short
Adult mosquitoes travel. The female Aedes aegypti that bites you in your backyard may have hatched in a neighbor's yard or in a wooded area nearby. A dunk in your bird bath does not stop mosquitoes that come from off your property. Most residential mosquito problems are a combination of on-site breeding and movement from the surrounding area.
Mosquitoes rest in shaded vegetation during the heat of the day: ornamental shrubs, the underside of deck boards, in dense ground cover. A barrier treatment applied to these resting spots knocks down the population of adults present and provides residual that affects new arrivals. Dunks do not address this.
Standing water on a lakeside lot or a property with even gentle drainage swales can include spots that are easy to miss: hollow stumps, the folds of a tarp, the area around an outdoor faucet that drips, a pile of yard waste holding moisture. Source reduction, meaning finding and eliminating those spots, is part of effective mosquito management.
What a Professional Treatment Includes
A professional mosquito service for a Highland Lakes property typically includes a barrier spray applied to the vegetation around the yard perimeter, in shrubs, under deck areas, and along the fence line. This knocks down active adults and leaves a residual. Some companies also use timed misting systems for ongoing release.
A good technician also walks the property looking for breeding sources, dunks or treats standing water that cannot be eliminated, and advises on any source reduction the homeowner can do. The combination of adult population knockdown and breeding interruption is what actually moves the needle on mosquito pressure.
Treatment frequency matters here. Mosquitoes repopulate from surrounding areas, and rainfall resets the situation. In the active season around the Highland Lakes (roughly April through October), service every 3 to 4 weeks keeps the population suppressed. A single spray in May is not going to hold through August.
When Dunks Are the Right Answer
If your property has ornamental ponds, bird baths, rain barrels, or a water feature that you want to protect from mosquito breeding, dunks are exactly the right tool. They are also appropriate for treating larger areas of standing water, like a seasonal low spot on the property, where an adult spray is less practical.
Pair dunks with source reduction (flip buckets, clear gutters, change bird bath water weekly) and a professional barrier treatment for the vegetation, and you are covering all three phases of the mosquito life cycle.