Larvicides are an insecticide used on mosquitoes that does not harm people, pets, or the environment. However, they are able to greatly reduce these blood suckers in your lawn, so you’ll want to know how to use larvicides to get rid of mosquitoes.
When you realize what mosquitoes can do, that they not only annoy you but can also transmit deadly diseases, you will have no hesitation in driving them away. But you don’t want to hurt your family and neighbors (we hope), pets (right?), or the environment (that your family and pets live in). That’s where larvicides come in: They stop mosquitoes, but not the rest of us.
How Larvicides Work
Larvicides go after larvae, the second life stage, stopping mosquitoes before they can mature into adults. To do this, larvicides are applied to mosquito breeding habitats.
Liquid larvicide products are applied directly to water using backpack sprayers and truck or aircraft-mounted sprayers. Tablet, pellet, granular, and briquet formulations of larvicides are also applied by mosquito controllers and homeowners to breeding areas around the home.
Larvicides kill mosquito larvae before they can grow into adults. There are different methods:
- Contact: Some larvicide products kill larvae on touch.
- Ingestion: Some larvicides work when ingested by the mosquitoes. Enzymes in the stomach of the mosquito turn the larvicide into a poison.
Apply Larvicides Where Mosquitoes Lay Eggs
Use larvicides in the places where mosquitoes lay eggs, which are places that hold water:
In Features Designed For Water
- Fountains, even if you let the kids play in it
- Ornamental ponds (with no fish)
- Ponds or other retention basins
- Swimming pools that are not chlorinated, and their covers
- Birdbaths. Most larvicides will not harm birds, but be sure to check.
In Items Meant to Catch Water
- Buckets
- Catch basin drainage system that collects rainwater or other runoff
- Cisterns of rainwater
- Gutters and downspouts
- Rain barrels
- Septic tanks
In Things That Really Shouldn’t Be There, But Are
- Low-lying areas that fill with stagnant water. (If it is there for only a week, mosquitoes may emerge.)
- Marshy areas on your property, but not in the wild (where other mosquito predators do the work)
- Tires that have been discarded or set aside. (If you find them on your property, it isn’t easy to discard them, but you should.)
- Tree holes. If you don’t want to apply larvicide, you can instead fill them with expandable foam.
- Ditches, especially along roads
In Items You Intend to Use
- Wheelbarrows you haven’t turned over
- Water cans left standing out
- Trash cans that don’t have lids (or have lids that aren’t being used)
- Outdoor furniture. Those chairs on the porch, for example, whether they are always left out or just not put away like you intended.
Treat Standing Water
Use larvicides to treat standing water that:
- Isn’t for drinking by people or pets. Many larvicides, including Bti, are safe for birds, though.
- Is just sitting there. Mosquitoes will lay eggs in just ¼-inch of standing water, and within a day or two of it showing up. That toy that was dropped in the yard a few days ago could well have larvae in it. So could any bit of water that isn’t covered, dumped, or removed.
Rain barrels are full of water, so how do you keep mosquitoes out of rain barrels? Install a fine mesh screen, or use a Bti larvicide if you can’t install a screen over the openings.
Select a Larvicide
Larvicides come in many forms:
- Liquids, applied on a small scale by hand sprayers or backpack sprayers, and on a large scale by trucks and airplanes.
- Tablets, such as mosquito dunks
- Bits
- Pellets
- Granules
- Briquettes
Types of Larvicides
Professionals consider there to be these types of larvicides:
Bacterial Larvicides
The following types of larvicides are made from natural substances.
- Bacillus thuringiensis israelensis (Bti) is a naturally-occurring bacteria found in the soil throughout the world. It is used to control mosquito larvae, and does not need a license to be used in your yard. It kills mosquito, black fly, and midge larvae but has not been found to affect human health
Bti products are available in hardware stores and garden centers. Common brand names are Mosquito Dunks, VectoBac, Aquabac, and Bactimos.
- Saccharopolyspora spinosa is a bacteria found in soil that is toxic to mosquitoes, as well as ants and other insects. Spinosad is a commercial larvicide derived from this bacterium.
- Lysinibacillus sphaericus (also known as Bacillus sphaericus) is also found in soil. It works well on some mosquito species but does not work on Aedes aegypti, the mosquito that transmits yellow fever.
Insect Growth Regulators
Insect growth regulators (IGRs) are insecticides* that prevent mosquitoes from reaching the adult stage. Methoprene and pyriproxyfen are examples of insect growth regulators. They work by interfering with the reproductive cycle of mosquitoes; the eggs might be laid, but they won’t hatch, for example.
*Although not a true larvicide since they can interfere with other stages of development as well, they do affect larvae and so are fitting in a discussion on larvicides.
Oils and Films
Oils and films can spread in a thin layer across the surface of water, often in a rain barrel, for example. Oils and films on the surface will smother larva and pupa, keeping them from reaching the adult stage of the mosquito life cycle.
What Larvicides to Use Where
A common-sense guideline for using larvicides:
- Bti larvicides are the choice of public health professionals to treat rain barrels, ponds, fountains, and large collections of water.
- Treat the water that gathers in leaves of bromeliad plants or other water-holding plants with a liquid or granular Bti larvicide. These plants are growing in popularity for the inside of homes, and continue to be popular for the outdoors in warm-weather regions. Keep this in mind for any strong, large leaves on which water will gather, indoors or out.
- Use a granular larvicide in the saucers under potted plants or other small containers.
Remember: Always follow the instructions on the label. Don’t give in to the temptation to “put in a little more” for any reason.
FAQs
An adulticide is an insecticide used to kill adult mosquitoes. You can apply them as a DIY project, but they can be dangerous enough (say, if too much is applied) that you should consider using a licensed pest control professional.
Also, it is expensive and is not especially effective. Government agencies will turn to it to fight mosquitoes if there is concern that an area is on the verge of an outbreak of a mosquito-borne disease. But it probably isn’t the way to deal with a problem in your yard. Larvicides help prevent mosquito populations from growing in your yard and community in the first place.
You will be able to see mosquito larvae, in part because mosquitoes lay hundreds of eggs at a time. But be aware of this: Mosquito larvae look like small worms.
Mosquitoes will not try to breed in a swimming pool that is being chlorinated. But if you drain your pool, water will gather in the bottom. In that case, apply larvicides.
Prefer to Hire a Pest Control Professional?
Prefer to have a pro tackle this job? Pest Gnome connects you to the best pest control experts in your area who can apply larvicides, adulticides, and keep your home and yard pest-free.
Main Photo Credit: frank600 / Canva Pro / License
