Mosquito Control San Antonio uses surveillance data to target mosquito populations most likely to cause disease. The program uses both temporary and permanent methods to prevent the spread of mosquito-borne diseases.
Organizations can drain or dump standing water, such as discarded tires, urns at cemeteries and rain barrels, and treat large bodies of water with larvicides, like methoprene or Bti (Bacillus thuringiensis israelensis). This eliminates larval habitat.
Source Reduction, which is a physical method of Mosquito Control, eliminates or reduces mosquito breeding habitats. It is the most effective and environmentally sound approach to controlling mosquitoes. Source reduction can include as simple as homeowners emptying water from containers around their homes and yard, or it may be as complex as regrading drainage ditches to prevent mosquito breeding sites or draining marshy areas to stop mosquito production. It can also involve community-wide activities like removing discarded tires, bird baths, buckets, plastic covers, toys, and other containers that can hold standing water.
In addition, it can include educating the public to change out standing water in fountains, bird baths, rain barrels, wading pools and potted plants every week to get rid of any mosquito eggs that have been laid there. It can also include a system of monitoring and maintenance of wetlands and other natural resources to prevent water stagnation.
Larviciding, which is a chemical method of controlling mosquito larvae, is used when eliminating oviposition sites with source reduction is not possible or practical. The chemicals used in larviciding are specifically designed to kill mosquito larvae. They are not as broad-spectrum as the insecticides used to control adult mosquitoes, so they are more environmentally friendly.
Some of the products that can be used as larvicides are Bti toxin, pyrethroids and insect growth regulators. These products are very specific to mosquitoes and other insects that lay their eggs in standing water, so they do not harm fish, birds, mammals or other organisms in the environment. However, as with any insecticides, resistance to these compounds can develop in mosquito populations.
Using fogging or ultra-low volume spraying (ULV) to control adult mosquitoes is another method of controlling them. ULV uses a very small amount of pesticide active ingredient in comparison to the area being treated and is delivered through specially designed nozzles that have been thoroughly tested for safety and effectiveness. The insecticides used in ULV are synthetic pyrethroids, including deltamethrin and lambda-cyhalothrin, and are usually applied at dusk when mosquitoes are most active. They are applied to the lower limbs of shade trees, shrubs and other vegetation and are blown through the air by compressed air sprayers.
Larviciding
Larviciding is the regular application of microbial or chemical insecticides to water bodies and containers to kill mosquito larvae. The purpose is to reduce the number of mosquitoes that develop into adults and bite people, thus reducing malaria transmission. It is a key component of an Integrated Pest Management (IPM) strategy.
The Anopheles vector mosquitoes lay their eggs in standing water, which must be available throughout the mosquito life cycle to support the growth of the developing larvae and pupae. The water is usually freshwater, but some species may prefer brackish habitats or riceland aquatic ecosystems (Tusting 2013). The standing water can be natural or man-made, temporary or permanent. Some species of Anopheles are found only in shallow streams or swamps while others are more commonly associated with ponds, tanks and unused swimming pools (Bruce-Chwatt 1985).
A larval control intervention can be applied through ground, aerial, or hand spraying. The chemicals used in larviciding are called larvicides, and they include stomach toxins, contact agents, surface agents and insect growth regulators. Larvicides are primarily used to target mosquito larvae in a body of water, and they are often mixed with water to ensure that the entire breeding site is treated.
Several studies of larviciding have been conducted and the evidence is mixed. Some studies show no benefit, while other studies suggest benefits in areas with well-defined, measurable targets for larviciding. One important issue is the timing of the larviciding, since it must occur prior to the time when the mosquitoes move to their adult stage and begin biting humans.
There is also the potential for contamination of the water supply by the larvicide, although if the oil is applied according to label directions, it poses no risk to human health. Some oils, however, can be toxic to fish and other aquatic wildlife, so the use of larvicides should be done with caution in sensitive habitats such as marshes and wetlands.
A recent Cochrane review of larviciding for malaria control found low-certainty evidence of an effect. It is important that the studies are rigorous, including controlled before-and-after (CBA) designs with a contemporaneous control arm and at least two sites per arm.
Biological Control
A mosquito that is not killed during a larval or pupal stage can lay thousands of eggs, which will eventually develop into disease-carrying adults. Controlling mosquito larvae and pupae using larvicides reduces or eliminates the need for adulticide spraying and other more intensive measures.
A biological control agent is a living organism that suppresses pests by competing with them for food, space or other resources needed for survival. Examples of biological controls include natural wasp parasites (like ladybugs), nematodes, bacteria and fish. Biological control is used to manage pests in agricultural, natural and urban areas.
For example, if stink bugs are damaging lychee flowers and fruit in an orchard, release of many more of the same species of natural wasps reared in an insectary will kill many more stink bug eggs and keep damage below the economic threshhold. This is a much more environmentally sound approach to managing pests than applying an expensive, toxic chemical pesticide to the entire orchard.
Another way to be a good neighbor is to support your local mosquito control program and do your part to protect yourself and your neighborhood from disease-carrying mosquitoes. Help clean up and maintain public spaces like parks and greenways. Organize community cleanup events to remove large items that collect water such as tires. Be sure to empty, scrub, turn over, cover or throw away items that hold water like buckets, planters, toys, birdbaths and flowerpot saucers.
Report ditches that have been filled with stagnant water for one week or more, as these may produce mosquito larvae and pupae. The District can help you locate and clear these ditches, or you can hire a private contractor to do so.
Mosquitoes can be controlled by using repellents, mosquito traps or larvicides. Repellants, traps and larvicides are most effective when they are used in conjunction with other IVM methods. It is important to use only the amount of repellent recommended on the label, and follow the directions on how to apply it properly. Before purchasing any insecticide, check the product label for the active ingredient and its safety information on a Material Safety Data Sheet.
Public Education
When people think of mosquito control, they often imagine trucks or airplanes spraying insecticide to kill adult mosquitoes. However, effective mosquito control requires a comprehensive approach that includes surveillance, source reduction, biological control, larviciding, and public education. Integrated Mosquito Management (IMM) programs that incorporate all of these methods reduce mosquito populations and protect human health while minimizing environmental impact.
The primary means of physically controlling mosquitoes on private property is to eliminate their breeding habitat. For example, homeowners can help by emptying and scrubbing containers that hold standing water around their house once a week. In addition, they can install drains in downspouts or corrugated drain pipes attached to gutters. District staff also works with large landowners to maintain or restore drainage systems to ensure proper water flow and hydration.
Other physical controls include improving tidal saltmarshes by restoring their natural hydrology and revegetating them with native grasses that can support fish and wildlife. In irrigated agriculture lands, water management practices that prevent soil compaction and promote good crop rotation are effective in decreasing mosquito numbers. In tidal saltmarshes, the District employs a technique called Open Marsh Water Management (OMWM) which involves constructing a network of shallow pools and ditches to replace tidal flow in mosquito-breeding areas without adversely affecting the tidal salt marsh ecology or habitat.
Larvicides are products that kill mosquito larvae before they become biting adults. The District uses these products in conjunction with source reduction to minimize the need for spraying of adult mosquitoes.
In addition, the District educates people about the importance of personal protection by encouraging them to use long sleeves and pants when outdoors. It is important to remember that just one mosquito bite can lead to a mosquito-borne disease like malaria, West Nile Virus, or Zika.
Most people can protect themselves by limiting their exposure to mosquitoes. Support your local mosquito control program and encourage neighbors to do the same. The District’s program relies on community involvement to be successful.