What We Do
The District controls mosquitoes in the County's wetlands and other breeding sources created by standing water in street catch basins, drains, roadside ditches, flood channels, ravines and similar places on public land. The procedures are routine larviciding operations throughout the year and treating for adults only when necessary. We work with city, county, state, and federal agencies toward permanent correction of these sources whenever it is advisable.
The Orange County Vector Control District does a number of things to control mosquitoes throughout the County.
Initially, and most importantly, the District does surveillance all over the County. If we don't know where the mosquitoes are we can't treat for them! the District has about 100 mosquito traps placed all through the County to collect mosquitoes to see how many are in that area as well as to test them for possible diseases they could be carrying (i.e. West Nile virus, St. Louis and Western Equine Encephalitis). Orange County Vector Control District uses two different types of traps: a carbon dioxide baited trap and a gravid mosquito trap. The carbon dioxide trap is used as an attractant for recently mated females. After females mate, they need to find a blood-source to be able to produce eggs. Carbon dioxide is what all animals exhale when they are breathing so the trap mimics a potential blood-meal to the mosquito. Every time you exhale when you are outside you are attracting mosquitoes! The gravid trap is a foul-smelling trap that egg-laying female mosquitoes are attracted to as a potential place to lay their eggs.
|Carbon Dioxide Trap
As well as the surveillance conducted by our lab every week, our Inspectors are also doing surveillance every day by looking for mosquito breeding sources in their areas. In between service requests, our Inspectors are checking drains, gutters, and ditches. Anything that can hold water for longer than one week has the potential to be a breeding source.
|Dipping to Locate Larvae
|Potential Mosquito Breeding Ditch
The District uses many different means of controlling mosquitoes:
- Source Reduction
Manipulating or eliminating potential mosquito breeding sources can provide a dramatic reduction in mosquito populations. District staff educate property owners as to ways in which they can remove these sources like by emptying containers holding water. Staff also works with large land managers to restore and maintain water flow or circulation in systems that become clogged with sediment and debris or over run with vegetation.
- Biological Control
The District's primary source of biological control is a little fish, the mosquito fish (Gambusia affinis). These fish are indispensable to our mosquito control program. They eat mosquito larvae as fast as the larvae hatch from their eggs. Mosquito fish are provided free of charge at our District for stocking ornamental ponds, unused or "out-of-order" swimming pools, and animal watering troughs. They feed themselves and care is limited to protecting them from garden sprays and from chlorine or other chemicals used to clean the pond. The District also stocks thousands of these fish each year in artificial lakes, reservoirs, waste water disposal lagoons, and drainage channels to eliminate the need for frequent spraying with a mosquito insecticide. The District is careful not to place mosquito fish where they could enter a natural system.
>>> Click for more information on Mosquito Fish.
Mosquito fish are a critical part of Orange County Vector Control District's integrated approach to mosquito control. Mosquito fish are opportunistic feeders, have a tremendous appetite for mosquito larvae, and are very effective at preventing the production of mosquitoes in isolated water containers or systems that are too large to dump out or easily drain. For example, these fish are ideal for controlling mosquitoes in non-chlorinated, out-of-service swimming pools and ornamental ponds. They should not be used in situations where they might escape into natural waterways and become pests, as these fish are not native to California and all distribution of these fish is regulated by the California Department of Fish and Game.
Mosquito fish grow to a maximum size of about 2 inches in length and typically live 2-3 years, but may exceed this lifespan if conditions are favorable. They are live-bearing and can produce up to 3-5 broods per year, with each brood containing from 30-100 young fish. Young fish will be eaten by larger fish unless they are provided with aquatic vegetation or other refuge that is dense enough to offer protection. Mosquito fish can tolerate a wide range of temperatures and water quality conditions, and are quite tolerant of pollution. They prefer sunlit areas of water and do not thrive in heavily shaded waters. The fish are more active during the summer. In the winter they become inactive, move to the bottom of water, and reduce their feeding.
Mosquito fish eat a broad range of food sources (e.g., plants and animals) and will consume most types of available prey; one fish is capable of eating over 100 mosquito larvae per day. Feeding these fish is not necessary unless stocking pond used to hold such fish is new and bare of vegetation. In this case, tropical fish flakes or other commercial fish food are suitable to use as feed.
To see a video of mosquito fish eating mosquito larvae, click here
To pick up your own mosquito fish, click here.
- Chemical Control
While, technically this is the chemical control category, the District uses biological agents for larval control. The District routinely applies "biorational" pesticides countywide to control mosquitoes. The term "biorational" relates to the application of naturally occurring mosquito pathogens and predators in a manner that provides effective mosquito control with the least amount of impact on the environment. Currently, the District uses several biorationals including two microorganisms, Bascillus thuringiensis israelensis (Bti) and Bascillus sphaericus plus an insect growth regulator, methoprene.
>>> Click for more information on Biorational Control.
Larvae & Adult Mosquito Control
Bacillus thuringiensis israeliensis and Bacillus sphaericus:
Both of these microorganisms produce natural metabolic by-products that are only toxic to mosquitoes and show no toxic effects on organisms other than midges and buffalo gnats. The latter two groups of aquatic flies are considered pests, particularly buffalo gnats that are well known for their painful bites and human blood feeding habits.
The protein toxins produced by these two bacteria control mosquitoes by destroying (rupturing) the gut of the larva (wiggler). Once ingested, death usually follows quickly within 24 hours and sooner under ideal conditions. Unlike B. sphaericus, which remains in the water and regenerates from the corpses of dead mosquito larvae, Bti is short lived and only effective for one generation of control. Under suitable conditions, B. sphaericus can remain effective for several generations and even longer.
Recent studies have indicated that when Bti and B. sphaericus are combined, overall control is enhanced. Together, the Bti reduces natural resistance to B. sphaericus and at the same time extends the effective period of one application from 10 days to over three weeks. Unlike Bti, which is least effective in polluted water, B. sphaericus is unaffected by organics and therefore, preferred for controlling mosquitoes like the Southern House Mosquito (Culex quinquefasciatus), which breeds throughout Orange County in foul water situations (storm drains, catch basins, etc).
Methoprene, a juvenile hormone mimic, and insect growth regulator (IGR) is an active ingredient in vector products. This products acts as a "natural hormone" of insects and effectively retards the completion of the life cycle of the mosquito. The IGR works by preventing the larva from transforming to the pupa (stage between the larva and adult) and/or the adult from emerging from the pupa. Methoprene is formulated in ways to provide both short and long-term control by one-time application mixtures and slow release presentations using granules and briquettes.
Another integral facet of vector control is education and outreach. The District participates in hundreds of outreach events each year to educate the public on vector control issues. The District has a website and uses social media as another means for educating the public on vector issues and what the homeowner can do to manage his/her vector problem. The District also gives presentations throughout the County to numerous groups and community organizations on vector topics. The District has pamphlets at the office that can be picked up or we can send them to a residence free of charge. The District has also created public service announcements for both radio and television to help educate the public on health issues.
>>> Click for more info on the District's outreach program.
The District offers some of the most comprehensive public vector education programs in the United States. Programs, including a large library of information pamphlets and "how to" instructions, are anchored by a dedicated Outreach Coordinator. District education programs are noted for their informative style, content, and professional delivery. Citizen groups, city counsels, and other public entities are encouraged to contact the District and request a program on vectors, on services provided by the District, or on what private citizens and commercial interests can do to prevent vectors. Programs emphasize rats, flies, mosquitoes, and Red Imported Fire Ants.
Educational Themes and Program Content
The intent of the District's education programs is to inform our citizens about vectors and how they impact human health, property, and life style. In addition, common sense pointers are explained to guide audiences to a reasonable understanding that vectors are "manageable" if proper exclusion and preventative measures are used.
If your school or civic organization is interested in having a vector program presented by the District, please contact Tawnia Pett at (714) 971-2421 Ext. 166 or at email@example.com.