Warmer weather means mosquito season is on the way

Posted at 10:02 AM, May 14, 2018
and last updated 2018-05-15 16:49:10-04

VIRGINIA BEACH, Va. - The warmer weather of May brings the beginning of mosquito season in Virginia and the Virginia Department of Health is urging caution.

Officials caution people to be mindful of the Zika virus, which can be spread by mosquitoes, as well as West Nile or Eastern equine encephalitis.

In Virginia Beach, Mosquito Control Biologist Jennifer Barritt has already been busy and expects the forecast this week to lead to more mosquitoes.

"Hot temperatures plus a lot of rain equals increase in mosquito counts. A lot more mosquitoes are going to be coming through in the next week to two weeks."

The Virginia Department of Health answers these frequently asked questions about mosquitoes:

Mosquitoes are biting me during the day when I am outside in my yard. What kind of mosquitoes are they and what can I do to get rid of them?
Most of the time (90% of the time) when Virginia citizens complain about being bitten by daytime biting mosquitoes, Asian tiger mosquitoes are to blame.  Asian tiger mosquitoes are one of the most common and widespread mosquitoes in Virginia.  Outdoors, they bite only during the daytime (sun-up to sundown).  They will sometimes bite after dark, but only when there is illumination from outdoor lights, or when they get indoors.  They only breed in containers or tree holes and would never be found breeding in puddles, ditches or ground pools.

The best way to eliminate Asian tiger mosquitoes is to eliminate all standing water in containers on your property. Replace the water in birdbaths and wading pools every week and take an inventory of your yard to identify any items such as buckets, tarps, clogged gutters, toys, tree-holes (e.g., knot-holes), etc., that may be holding water and providing a breeding habitat for these mosquitoes.

There are a lot of puddles in my neighborhood with standing water. How can I tell if the mosquitoes that are biting me are breeding in those puddles?
If the water stands for more than a week and mosquitoes are biting you after sundown, the mosquitoes might be a species that breeds in puddles, roadside ditches, or storm-water management basins.  Very few of the mosquito species that bite during daylight hours comes from roadside ditches or puddles. There are no daytime biting species that would breed in a permanent body of water such as a lake, farm pond or storm-water management pond.

Are there other mosquitoes that bite during the day besides the Asian tiger mosquito?
The predominant daytime biting mosquito species around residential property is the Asian tiger mosquito. There are a number of mosquito species that breed in woodland flood pools or forest puddles that will bite during the daytime in the shade of forest or under open sky on overcast days.  Most of these woodland pool species will only be a problem when the breeding habitat is in forest that is contiguous with the citizen’s residence.

There is a large, aggressive, daytime biting mosquito species (the dark rice-field mosquito) that most commonly breeds in puddles that occur in open sun light, i.e., fields or forest clear-cuts..  It attacks in broad daylight.  It can also sometimes be found breeding in roadside ditches and wheel rut puddles.

Two of the species that breed in salt marshes will bite during daylight hours.  One of these salt-marsh species bites only in the shade of trees, or under open sky on overcast days; the other may sometimes bite humans in broad daylight when their resting habitats are disturbed.

Do these mosquitoes behave differently from one another?
Asian tiger mosquitoes are persistent biters, but they are also cautious and sneaky.  They will often flit away in response to a sudden movement, and generally, they bite only when people are standing relatively still, or moving slowly.  They tend to bite the ankles, legs and backs or undersides of arms where they are less likely to be noticed.

Many of the woodland pool species are fairly aggressive and will try to bite a person on the head, face or upper body even when that person is walking. Dark rice-field mosquitoes and salt marsh mosquitoes can be very aggressive biters and will try to bite a person even as the person is running or waving a broom at the mosquites.

Do ponds and lakes breed mosquitoes?
If it is a permanent body of water (such as a lake or pond), it is much less likely to be a source of mosquitoes than if it were a temporary body of water such as a puddle.  A puddle three inches deep and three feet in diameter can easily produce 10 to 20 times as many mosquitoes as your average 1-acre farm pond.

Permanent bodies of water develop resident populations of predatory species (aquatic insects, fish, salamanders) that reduce or eliminate the mosquito larvae in that environment.  Most mosquito species would not even lay eggs in a permanent body of water.  Several species of mosquitoes can breed in permanent bodies of water, but most of these have not been implicated in West Nile virus transmission.

Do mosquitoes breed in flowing water?
If the water in a ditch is flowing, it is not likely to produce any mosquitoes. The only species that might be found in a flowing ditch are not species known to transmit West Nile virus.  If the water has no flow (is stagnant) it could be an important source of mosquitoes.

How long can water stand in puddles or containers before it poses a problem?
If the water stands for less than a week it will not breed mosquitoes.  Only one species of mosquito (the dark rice-field mosquito) can complete its aquatic life cycle in less than seven days.  It is not a common mosquito, and it would probably not lay eggs in a puddle that would dry up so quickly.  Most mosquito species require standing water for a minimum of 10 to 14 days to complete their development.  Puddles that stand for less than a week are not worthy of concern.

Will mosquitoes breed in the holes left in my yard from downed trees?
Holes left by root balls may provide breeding habitat for mosquitoes if the water stands in the holes longer than a week. Standing water and organic matter, such as decaying leaves, provide ideal habitat for mosquitoes to breed. Fill such holes with topsoil. Holes in which water drains within a week are not a risk.

The Virginia Department of Health also has these tips to help prevent the spread of Zika:

  • Tip, Toss and Cover: Tip containers such as garbage cans, pool covers and flower pots that might collect water where mosquitoes could breed; toss outside items that aren’t being used and might collect water; and cover your skin with an EPA-registered insect repellent and long, light-colored clothing, shoes and socks.

  • CDC recommends that pregnant women not travel to any area where there is a risk of Zika virus infection; up-to-date travel advisory information can be found on the CDC website.

  • It’s important that travelers returning to the U.S. from Zika affected areas of the world take steps to prevent mosquito bites for 3 weeks so they don’t pass Zika virus to mosquitoes that could spread the virus to other people.

  • Stay up to date on ways to prevent sexual transmission of Zika virus disease; All pregnant women with sex partners who live in or traveled to an area with risk of Zika should use condoms during sex or abstain from sex for the remainder of their pregnancy; All other couples in which a partner has traveled to a Zika affected area can reduce the risk of sexual transmission by using condoms or abstaining from sex; Please visit the VDH website or the CDC website for the most up-to-date recommendations.