Pest Mosquitoes
Major Pest Mosquitoes in Indian River County
There are over 60,000 acres of citrus groves in Indian River county. Most were designed with deep irrigation furrows, called swales, between each row of fruit trees. When grove owners flood irrigate (completely fill every grove swale with water) or a heavy rain occurs, several species of pest mosquitoes begin to breed immediately.
The most common species here is the aptly-named Aedes vexans which is a major pest to humans. Aedes vexans mosquitoes can fly nearly ten miles from their breeding sites if conditions are right, so the mosquito which bites you today may have come from across the county. This species, fortunately, tends to bite only within two very narrow time periods … immediately after dark and again immediately before dawn. The rest of the time, Aedes vexans hides within the vegetation. This species is not much affected by cold temperatures and will breed even during the winter months if given the opportunity. Another species which commonly breeds in citrus groves is Culex nigripalpus, the main vector for Saint Louis Encephalitis (SLE) in this area.
Woodland areas and especially pastureland is prone to breeding the Psorophera columbae mosquito in huge quantities after a heavy rainfall. There are occasional reports of cattle and horses actually choking to death from breathing in these mosquitoes, so great can be the numbers. While this species is a major pest, it also is short-lived and generally disappears on its own within a week. Unlike Aedes vexans, it is relatively sensitive to temperature and will not breed or fly if the thermometer falls below 65 degrees. Because of this, P.columbae is not a major problem during the winter months.
In the easternmost part of the county, most pest mosquitoes come from the coastal salt marshes and related low-lying woodlands. The primary pest species in this area is Aedes taeniorhynchus and it is a ferocious biter which breeds in great numbers. Click here for more information about salt marshes. As a general rule for Vero Beach, mosquitoes found west of 27th avenue come entirely from groves, pastures and woodlands while those found east of this line are generally a mix of western and salt-marsh species. Like A.vexans, A. taeniorhynchus can also fly many miles from its source.
Other Pest Mosquitoes and Breeding Locations
There are over 60 different species of mosquito found in Indian River county. Most bite. Fortunately, our pest problem involves only a few species such as those detailed above. However, there are a few special cases worth discussing here:
Aedes aegypti and Aedes albopictus : These mosquitoes breed in small containers which hold stagnant water such as old tires, drink cans, kiddie pools and flower pots. Both of these mosquitoes do not fly far and an infestation can usually be traced to a breeding location within a few hundred feet. Both are opportunistic biters, zinging in for a quick bite and then away before they can be swatted. Of the two, A.albopictus (the “asian tiger mosquito”, a recent import to the area) isthe greater pest. Eliminating the offending containers is the best means of controlling these mosquitoes and is something every homeowner should do themselves. A.aegypti has been associated with yellow fever and A.albopictus is a known vector for dengue fever in the Caribbean area.
Wyeomyia vanduzeei and mitchelli : This species breeds almost exclusively in plants which can hold water, especially “pitcher plants” such as bromeliads. Breeding also occurs in some types of air-plants. This species is most common on our barrier island and differs from most other mosquitoes in that it is almost exclusively a daytime biter. By combining considerable resistance to pesticides,a sheltered habitat and daytime activity, Wyeomyia has proven almost impossible to control. Fortunately, its habitat and range are rather limited and homeowners can do much to control breeding by spraying or eliminating bromeliads on their property.
Mansonia (several subspecies) : This mosquito is found mostly in the western areas of the county and breeds in canals containing water hyacinths. Mansonia larvae never come to the surface of the water. Instead they have a special breathing tube which punctures air pockets in the water hyacinth. The adults are severe biters. Controlling aquatic weeds is the only effective measure to stop Mansonia from breeding. So far, prime Mansonia habitat lies west of Interstate-95,but as commerce and housing slowly invades that territory, Mansonia will become a noteworthy mosquito problem.
Culex quinquefasciatus : “Qwinks” prefer foul and nasty water to breed in. They are a common problem around sewage retention ponds, or from overflow from such ponds. They can also be found in some slow-flowing drainage ditches.
Anopheles quadrimaculatus : “Quads” are associated with small fresh waterpools and runoff areas.
Culex nigripalpus : This is the primary vector for Saint Louis encephalitis (SLE)in this area. It breeds in citrus grove swales and nearby pools of stagnant water. C.nigripalpus has a strong preference for biting birds and rodents. However, if a human is available, they will sometimes bite people too.
They breed in spectacular numbers when groves are flood-irrigated or after a heavy rainfall, especially in the summer and fall months. C.nigripalpus is a long-lived mosquito and can survive though the winter. The females will retain their eggs until a very heavy rain occurs. After laying their eggs, they will immediately go out in search of fresh blood.
It is in this between-rains period that C.nigripalpus can build up a large concentration of the SLE virus in their,bodies, making them a hazard to humans when they go seeking blood.
There are many other species of pest mosquitoes, but those named above compromise the greater percentage of problems in our county.
Contrary to popular opinion, the deeper canals and ponds do not breed significant numbers of mosquitoes. The reason for this is that larger bodies of water also are host to minnows and tadpoles which feed on the mosquito larvae. The only mosquitoes which survive well in deep canals are Mansonia, and that is because they hide within water plants, out of reach of their predators.