Mosquitoes

Mosquitoes are among the most serious of insect pests that have a direct impact on humans by transmitting microbial organisms that cause disease and death. Among the deadly diseases carried by mosquitoes worldwide are malaria, yellow fever, dengue fever, and encephalitis (an inflammation of the brain). In California, the primary reasons for controlling mosquitoes are to lessen the annoyance caused by their bites and to reduce the transmission of human and horse viral encephalitis and dog heartworm.

Biology and Identification

Mosquitoes are true flies, belonging to the family Culicidae in the order Diptera. The most important genera are Aedes, Anopheles, Culex, Culiseta, and Ochlerotatus. Mosquitoes have four life stages-egg, larva or "wiggler," pupa or "tumbler," and adult. The egg is laid on or near water, or where water will eventually cover it. The larva and pupa live under water, while the adult lives on land.

Some mosquitoes feed during the day, some at dusk, others at night. Adult mosquitoes are small (ranging from 1/8 to 3/4 of an inch long), slender, long-legged insects with a single pair of wings. All mosquitoes have a long piercing mouthpiece called a proboscis, which is used for feeding.

Detection and Monitoring

All mosquitoes require still water on which to drop their eggs. In urban areas, the most likely larval breeding areas are artificial containers or other small bodies of water such as storm and sewer catch basins and roadside ditches. Use a long-handled dipper to check water for mosquito larvae in ornamental ponds and other standing water.

Health Concerns

Several of the 48 known species of mosquitoes in California can carry disease under the right conditions. There are two forms of viral encephalitis, St. Louis and Western Equine, transmitted by mosquitoes in California. Dog heartworm is a deadly heart and pulmonary disease transmitted by tree hole mosquitoes. There is no direct evidence that mosquitoes are capable of carrying the AIDS virus.

IPM Approaches to Mosquito Management

Elimination of all standing water is the key to preventing mosquitoes from breeding. Use physical methods to exclude mosquitoes, and biological and chemical methods to provide long-term control.

Elimination of Water Sources

• Remove and dispose of all unused containers that would collect rain or water from sprinklers.
• Discard old tires or cut them in half to prevent water accumulation.
• Drain and overturn any small boats.
• Drain water from tree-holes and fill with sand or cement.
• Keep roof drains and gutters clear of debris.
• Empty bird-baths every three days.
• Root outdoor plant cuttings in sand, dirt, or vermiculite rather than standing water.

Physical Control Options

• Screen windows, doors and porches.
• Fill gaps around window and doors with weather-stripping.

Biological Control Options

• Stock ornamental ponds and horse troughs with mosquito-eating fish. Contact the closest mosquito abatement district for fish availability.

Chemical Control Options

• Use refined larvicidal oil such as Golden Bear 1111® to apply a film of oil to the surface of the water. The oil clogs the larval mosquito's breathing tube and suffocates it.
• Use bacillus-based products such as Bacillus thuringiensis (Bti) or Bacillus sphaericus to treat the early immature stages of the mosquitoes.
• Use the insect growth regulator methoprene to treat the later immature stages of the mosquitoes and prevent them from reaching adulthood.

* Bacillus-based products are only effective against the mosquito's 1st an 2nd immature stages. Methoprene is effective on the 3rd and 4th immature stages.

Facts About Mosquitoes

• All mosquitoes must have water in which to complete their life cycle.
• Seven days are required to complete the mosquito's life cycle (egg to adult) during warm weather.
• Only the female mosquito bites to obtain a blood meal. The male mosquito feeds only on plant juices.
• The female mosquito may live as long as three weeks during the summer or many months over the winter in order to lay her eggs in the following spring.