Submitted by Greater L.A. County Vector Control District
The brisk winter months are perfect for warm sweaters and fashionable scarves for LA County residents. But, there are some tiny, winged residents who hate the cold and find sanctuary in an unsuspecting place. If you are thinking these residents are mosquitoes, you are correct! Many mosquitoes retreat from the cold weather to find refuge in the underground storm drain system through the winter.
While we do have mosquitoes year-round in southern California, most species do not like cold weather, and their activity decreases significantly when temperatures drop below 50°F. Underground storm drains keep a consistent temperature about 70°F with high humidity, which creates an ideal climate for mosquitoes during the winter. To make sure these mosquito populations are controlled, the District’s Underground Storm Drain (USD) crew monitors and treats storm drains that breed throughout the year.
With the detection of invasive Aedes mosquitoes in LA County, such as the yellow fever mosquito (Aedes aegypti), the District is on high alert to assess the extent of their reproduction and survival in the USD system. Using encephalitis vector surveillance (EVS) traps, our underground crew and lab staff can capture mosquitoes in affected areas. In addition to assessing the native mosquito population, EVS traps have proven to be a useful tool in monitoring invasive species in the USD, according to Harold Morales, vector ecologist.
Thus far, yellow fever mosquitoes have been found on two separate occasions in the USD. The finding of these mosquitoes underground means that we need to diligently monitor the USD to contain and eliminate these vectors. As we continue through the winter months, residents can help by reporting day-biting, black-and-white mosquitoes in and around the home to vector control at ReportMosquitoes.org or calling (562) 944-9656, and by not littering or sweeping leaves and debris into gutters or storm drains.
