The label is the law. Read your product's label before you mix or apply; the rates here come from the labels listed under Sources.
- Active ingredient
- Lysinibacillus sphaericus (Bacillus sphaericus 2362, serotype H5a5b, strain ABTS 1743)
- Chemical class
- A microbial insecticide. Strain 2362 was isolated in 1981 from an adult blackfly in Nigeria and first registered in the United States in 1991. Its spores contain a protein that damages and paralyzes the gut of mosquito larvae that ingest them, so the larvae starve.[2]
- Mode of action
- IRAC Group 11B: Microbial disruptors of insect midgut membranes: Bacillus sphaericus[6]
- Signal word
- VectoLex FG Biological Larvicide Fine Granule (also sold as VectoLex CG and VectoLex G): Caution[1]
Bacillus sphaericus or Lysinibacillus sphaericus?
They are the same bacterium. In 2007 microbiologists described a new genus, Lysinibacillus, whose strains differ from the type species of Bacillus in their cell wall chemistry, and proposed transferring Bacillus sphaericus to it as Lysinibacillus sphaericus. EPA's fact sheet and the VectoLex label still use the older name, so product labels list it as Bacillus sphaericus.[5][2][1]
How it compares with Bti
A 2007 review by a USDA Agricultural Research Service scientist calls Bti and B. sphaericus formulations the main non-chemical means of controlling mosquito larvae in several parts of the United States and other countries. B. sphaericus has been used mostly against Culex mosquitoes in water rich in organic matter, though it is also active against numerous species in several genera and in cleaner water.[4]
The review notes that B. sphaericus persists longer than Bti in polluted water and, under certain circumstances, can recycle in dead larvae. Its drawbacks: mosquitoes in the Stegomyia group aren't susceptible to practical doses, and some populations of Culex quinquefasciatus and Culex pipiens have become resistant to it.[4]
Because both bacteria work well and are relatively specific, the review says either can be an ideal control agent in integrated programs, especially ones that combine other biological control agents, environmental management, personal protection and judicious use of insecticides.[4]
Where it is used
EPA lists the bacterium among the bacterial larvicides for mosquito control, alongside Bacillus thuringiensis israelensis (Bti): insects exposed to these Bacillus species have trouble digesting the food they eat.[3]
Its use sites are habitats where mosquitoes live and lay eggs, such as storm water and drainage systems, coastal areas, lakes and streams, water in discarded tires, and some crop sites such as rice fields. EPA says products stay active for one to four weeks, depending mainly on the mosquito species, environmental conditions, water quality and the form of the granules.[2]
The label's species list includes Culex species, Aedes vexans, Aedes triseriatus, Aedes sollicitans, Aedes melanimon, Aedes stimulans, Aedes nigromaculis, Psorophora columbiae, Psorophora ferox, Anopheles quadrimaculatus and Coquillettidia perturbans, including many of the mosquitoes known to carry West Nile virus.[1]
Outside the residential sub-label, the same product is applied with aerial or ground equipment to wastewater, storm water and drainage systems, salt marshes and other coastal areas, lakes, ponds, rivers and canals, dormant rice fields and some crops at 5 to 20 pounds per acre, using 10 to 20 pounds where longer control is needed or the water is deep or densely covered.[1]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| VectoLex FG Biological Larvicide Fine Granule (also sold as VectoLex CG and VectoLex G)[1] | Valent BioSciences Corporation | 73049-20 | 7.5% | fine granule | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| VectoLex FG Biological Larvicide Fine Granule (also sold as VectoLex CG and VectoLex G) | Standing water around the home (residential sub-label sites) | Mosquito larvae (Culex species, Aedes vexans and other listed species) | 1 lb product per 2,178 sq ft[1] Same rate as 1/4 lb (1/2 cup) per 544 sq ft or 1/8 lb (1/4 cup) per 272 sq ft; reapply every 1 to 4 weeks. |
How to apply it, step by step
1. Protective gear
- This is a CAUTION-signal product: it causes moderate eye irritation and is harmful if absorbed through the skin or inhaled. Wear protective eyewear, avoid getting it on your skin or clothing, and avoid breathing the dust.[1]
- Wash thoroughly with soap and water after handling it and before eating, drinking, chewing gum, using tobacco or using the toilet. Take off contaminated clothing and wash it before wearing it again.[1]
2. Before you spray
- Find the standing water where mosquitoes breed. The residential sites include ponds, water gardens, bird baths, fountains, flower pots and planters, tree holes, urns, rain barrels, pool covers, gutters and drains, wheelbarrows, garbage cans and covers, discarded tires, unused or abandoned pools and spas, flooded basements, and any other place where water stands for a while.[1]
- Don't apply it to treated, finished drinking water reservoirs or drinking water receptacles when the water is meant for people to drink. It can go into water that holds fish, other aquatic life and plants, and into areas used by people, pets, horses, livestock, birds or wildlife.[1]
3. Mixing
- There's nothing to mix: the granules are sprinkled straight from the package. Check the expiration date, which is two years from the date of manufacture.[1]
4. Applying
- Sprinkle the granules evenly at 1 pound per 2,178 square feet. For smaller areas the label scales that down: 1/2 pound per 1,089 square feet, 1/4 pound (1/2 cup, 4 ounces or 8 tablespoons) per 544 square feet, or 1/8 pound (1/4 cup, 2 ounces or 4 tablespoons) per 272 square feet.[1]
5. After you spray
- Reapply at intervals of 1 to 4 weeks.[1]
- Mosquito numbers may stay down longer where enough aquatic invertebrate parasites and predators live in the water, because the product doesn't affect them and they help reduce the mosquitoes.[1]
First aid
- In the eyes, hold the eye open and rinse slowly and gently with water for 15 to 20 minutes, removing contact lenses after the first 5 minutes. On skin or clothing, take off contaminated clothing and rinse the skin right away with plenty of water for 15 to 20 minutes. In either case, call a poison control center or doctor for treatment advice.[1]
- If inhaled, move the person to fresh air. If the person isn't breathing, call 911 or an ambulance, then call a poison control center or doctor for further advice. Have the container or label with you; the label's 24-hour number for emergency medical treatment information is 1-877-315-9819.[1]
Storage, spills and disposal
- Store it in a cool, dry place, and don't contaminate water, food or feed by storage or disposal.[1]
- Don't reuse or refill the container. Put an empty one in the trash or offer it for recycling; for a partly full one, call your local solid waste agency for disposal instructions, and never put unused product down any indoor or outdoor drain.[1]
From the safety data sheet
- Valent BioSciences' safety data sheet for VectoLex FG (EPA Reg. No. 73049-20; revision 3, issued January 8, 2020) lists 7.5% Bacillus sphaericus 2362, serotype H5a5b, strain ABTS 1743 fermentation solids, as tan to brown fine granules with a characteristic odor. Its OSHA hazard classification is eye irritation, Category 2B, with the signal word WARNING; the EPA label signal word it gives is CAUTION.[7]
- Its toxicology section reports an oral LD50 above 5,000 mg/kg, a dermal LD50 above 2,000 mg/kg and an inhalation LC50 above 0.09 mg/L, the highest concentration that could be reached. It rates the product slightly irritating to skin and a Category 1A skin sensitizer, says it isn't corrosive or pathogenic, and notes that none of its components are listed as carcinogens by NTP, IARC or OSHA.[7]
- For handling, the sheet calls for a dust mask, protective clothing including boots and gloves, and goggles, safety glasses with side shields or a full-face shield when splashing or spraying is likely. Where respiratory protection is warranted during application or with repeated exposure, it names a NIOSH-approved respirator with any N, P, R or HE filter. Don't eat, drink, chew gum or smoke while working with it, and wash thoroughly afterward.[7]
- Keep it in the original container, closed when not in use, in a dry, cool place where it's protected from physical damage. Sweep up spills into a container for disposal without raising dust.[7]
- Its ecological data, for the concentrated technical powder, include 96-hour LC50 values above 15.5 mg/L for rainbow trout and bluegill and an acute oral value above 9 g/kg for mallards. It calls the product essentially non-toxic to bees and not pathogenic to non-target organisms.[7]
- The sheet says no EPA hazardous waste number applies and the product, if discarded, isn't expected to be a characteristic or listed hazardous waste; dispose of it under federal, state and local rules.[7]
Safety and environmental hazards
People
Signal word CAUTION: the label says the granules cause moderate eye irritation and are harmful if absorbed through the skin or inhaled, so wear protective eyewear and avoid breathing the dust. EPA's fact sheet says no harmful effects are expected for the public when products are used according to label directions, but because of possible skin and eye irritation, applicators should avoid direct contact with the granules or a concentrated spray mix.[1][2]
Pets
The label says VectoLex FG can be applied to areas used by or in contact with people, pets, horses, livestock, birds or wildlife, and its residential sites include bird baths and livestock watering troughs. EPA's fact sheet says tests revealed no expected harm to non-target organisms.[1][2]
Bees and pollinators
EPA's fact sheet says tests revealed no expected harm to non-target organisms. The label carries no bee statement.[2][1]
Fish and water
The label allows use in water that contains fish, other aquatic life and plants, and says non-target aquatic invertebrate parasites and predators aren't affected by the product. The one water restriction is treated, finished drinking water: EPA says products with this bacterium aren't registered for use in or on treated or finished drinking water for human consumption.[1][2]
Common questions
- How much VectoLex FG do I use?
- The residential rate is 1 pound per 2,178 square feet, sprinkled evenly. For smaller areas use 1/2 pound per 1,089 square feet, 1/4 pound (1/2 cup) per 544 square feet, or 1/8 pound (1/4 cup, 4 tablespoons) per 272 square feet.[1]
- How often do I need to reapply it?
- Every 1 to 4 weeks, according to the label. EPA says products with this bacterium stay active for one to four weeks, depending on the mosquito species, the water and the conditions.[1][2]
- Can I put it in a rain barrel or bird bath?
- Yes, both are on the residential sub-label's list of sites. The exception is drinking water: don't use it in treated, finished drinking water reservoirs or drinking water receptacles when the water is meant for people to drink.[1]
- Will it hurt fish, birds or pets?
- The label says it can be used in water with fish, other aquatic life and plants and in areas used by pets, horses, livestock, birds and wildlife, and EPA's fact sheet says tests revealed no expected harm to non-target organisms. The granules themselves can irritate eyes and skin, so keep them off your skin and wear eye protection when you apply them.[1][2]
Sources
- U.S. EPA Pesticide Product Label System, “VectoLex FG Biological Larvicide Fine Granule (Sub-Label C, residential use) label, EPA Reg. No. 73049-20 (EPA-stamped, Feb. 25, 2015).” www3.epa.gov/pesticides/chem_search/ppls/073049-00020-20150225.pdf (accessed 2026-11-08)
- U.S. EPA Office of Pesticide Programs, “Fact Sheet: Bacillus sphaericus 2362, serotype H5a5b, strain ABTS 1743 (PC Code 119803), May 6, 2014.” www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-119803_06-May-14.pdf (accessed 2026-11-08)
- U.S. EPA, “Controlling Mosquitoes at the Larval Stage (last updated February 26, 2026).” www.epa.gov/mosquitocontrol/controlling-mosquitoes-larval-stage (accessed 2026-11-08)
- Journal of the American Mosquito Control Association (author: USDA Agricultural Research Service), “Lacey LA. Bacillus thuringiensis serovariety israelensis and Bacillus sphaericus for mosquito control. J Am Mosq Control Assoc 2007;23(2 Suppl):133-163 (PubMed abstract).” pubmed.ncbi.nlm.nih.gov/17853604/ (accessed 2026-11-08)
- International Journal of Systematic and Evolutionary Microbiology, “Ahmed I, Yokota A, Yamazoe A, Fujiwara T. Proposal of Lysinibacillus boronitolerans gen. nov. sp. nov., and transfer of Bacillus fusiformis to Lysinibacillus fusiformis comb. nov. and Bacillus sphaericus to Lysinibacillus sphaericus comb. nov. Int J Syst Evol Microbiol 2007;57:1117-1125 (PubMed abstract).” pubmed.ncbi.nlm.nih.gov/17473269/ (accessed 2026-11-08)
- Insecticide Resistance Action Committee, “IRAC Mode of Action Classification Scheme, Version 11.5 (Feb. 2026).” irac-online.org/documents/moa-classification/ (accessed 2026-11-08)
- Valent BioSciences LLC (copy in Sumitomo BioRational's upload folder, linked from Valent's public-health site), “VectoLex FG Biological Larvicide Safety Data Sheet (Valent BioSciences, SDS# VBC-0046, Revision 3, issued January 8, 2020; EPA Reg. No. 73049-20).” www.sumitomobiorational.com/wp-content/uploads/2026/04/SDS-VBC-0046R3-VectoLex-FG-01-08-20.pdf (accessed 2026-11-08)