Bacillus thuringiensis israelensis (Bti) is a naturally occurring soil bacterium used as a highly specific biological control agent worldwide. This microbe produces protein crystals that are toxic only when ingested by the larvae of mosquitoes and black flies. Bti is often the preferred method for controlling these pests because its targeted mechanism does not harm mammals, fish, birds, or most non-target insects like bees. It represents an environmentally conscious approach to reducing insect populations before they mature into biting, adult pests.
Identifying the Right Product Forms
Bti is formulated into several commercial forms designed for specific application environments. The most recognized form for homeowners is the briquette, often called a “Mosquito Dunk.” This small, solid wafer floats and slowly releases Bti over a period of up to 30 days. Briquettes are ideal for long-term standing water sources like rain barrels, ornamental ponds, or septic tanks that cannot be easily drained.
Another common product type is Bti granules, which are small, corn cob-based particles designed for rapid action. When sprinkled over water, these granules sink and quickly release the Bti, providing a fast kill of existing mosquito larvae, often within 24 hours. Granules are particularly useful for treating temporary puddles, flower pot saucers, or areas where water collects but does not persist long-term.
For larger properties, municipal programs, or commercial agricultural use, Bti is often sold as a liquid concentrate. This concentrated suspension is designed to be diluted and then sprayed over large areas of standing water, such as stormwater retention ponds or ditches. The liquid form allows for efficient, broad-scale coverage using backpack sprayers or specialized aerial application equipment.
Retail and Online Purchase Locations
The easiest place for homeowners to purchase Bti products is at local retail sources specializing in garden and home maintenance. Hardware stores, home improvement centers, and garden supply nurseries widely stock consumer-sized packages. You will typically find the solid forms, such as Mosquito Dunks and Mosquito Bits, in the pest control or garden center aisle.
For customers seeking a wider selection or bulk ordering, specialized online retailers offer a significant advantage. These vendors focus specifically on pest control, biological solutions, or organic gardening and carry a more extensive inventory. They are the best source for purchasing liquid concentrates or larger volume packages of granules and briquettes.
When large quantities are needed, such as for property management or agricultural applications, consider agricultural or bulk chemical suppliers. These companies often sell trade-name products like Vectobac, Teknar, or AquaBac in large containers, such as 40-pound bags of granules or multi-gallon drums of liquid concentrate. Buying from these suppliers usually requires a commercial account or bulk purchase volume.
Essential Application Guidance
Since the bacterium must be actively ingested by the feeding larva, Bti is only effective in standing water where mosquito and black fly larvae are present. Applying Bti to dry areas or surfaces will not provide any control against adult mosquitoes or emerging pupae.
Dosage is determined by the specific product form and the volume of water being treated, so consulting the label is mandatory. A single briquette is typically rated to treat a specific surface area of water, while granules are broadcast at a rate measured per square foot or acre.
Because Bti breaks down relatively quickly under environmental conditions, especially with exposure to sunlight and water flow, reapplication is necessary to maintain control. Most briquette products offer residual activity for 30 days. Granules may require reapplication every 7 to 14 days, depending on the water conditions and the product formulation. Establishing a consistent reapplication schedule is the most effective way to interrupt the pest’s life cycle.