As if a pandemic isn’t enough to handle for 2020, now the East Side Mosquito Abatement District has identified a brand new threat to the area — the yellow fever mosquito has landed in Modesto, expanding its range to Stanislaus County.
The new mosquito species, Aedes aegypti, was trapped in Modesto in July and is in the same vector as the Zika, Dengue, Chikungunya viruses.
This new mosquito as, unlike other Aedes mosquitoes that grow in pastures, grows in small containers within residential areas and often inside homes. It exclusively bites on people and does so during daytime.
While it may be disturbing to some to discover a new mosquito species buzzing around potentially carrying a dangerous virus, residents may have noticed the sheer volume of the pesky blood-suckers swarming unsuspecting hosts the minute they stepped outside.
“Since the start of September, we have received a total of 149 service requests from Oakdale, the bulk of these calls were received within the last two weeks,” shared Dr. J. Wakoli Wekesa, District Manager/Entomologist for the East Side Mosquito Abatement District. “The Valley Home area had 70 calls, and north of Stanislaus River eastwards to Knights Ferry had 31 calls within the same time period. The heavy volume coincided with the shaking of almond trees on the Northwest and mostly around the City of Oakdale and (was) made worse by the prevailing wind pushing mosquitoes into town.”
In case you thought you were imagining the surge of mosquitos, you weren’t — the hungry mosquito population had, indeed, exploded, causing aggressive swarming at area parks and anywhere near water.
It’s a problem every year that keeps the East Side Mosquito Abatement District fielding calls and sending out abatement teams to treat trouble areas.
According to Dr. Wekesa, the District has a proactive program of conducting mosquito surveillance – trapping adults and monitoring abundance of larvae and adult mosquitoes in the area so that they can act before there is a major mosquito problem. Surveillance is conducted once a week, the mosquitoes trapped are identified and tested for West Nile virus. The other mosquito control program consists of operations, involving two technicians, one focused on finding above ground breeding sources and applying larvicides to control them before they hatch, and the other is focused underground with one technician conducting curb rigging operations to control mosquitoes in underground storm drains, channels and swales in parks, roadside ditches, and road underground systems.
“Once in a while when adult mosquitoes increase in the neighborhoods, especially from nearby orchards the district conducts adulticides sprays to kill adult mosquitoes so folks are not bitten in town,” Dr. Wekesa explained. “We also have two airplanes that the District uses to spray open fields on the outskirts of town to alleviate biting pressure on folks. The service request calls over the past two weeks was a flare up of adult mosquitoes from almond orchards on the northwest of town and also along the Stanislaus River.”
Spraying larvicide is an ongoing process to keep mosquito populations low but over the last two weeks, the District had to conduct ultra-low volume spray using two truck-mounted sprayers in the City of Oakdale on three mornings between 4 a.m. to 7:30 a.m., Sept. 16 through 18.
“We sprayed mostly the north and northwest side of Oakdale the morning of Sept. 16 and 17, and southwest, south and northeast side on Sept. 17 and 18,” Dr. Wekesa said. “A total of 390 acres were sprayed over the three mornings and we believe relief was established in those neighborhoods.”
The District traps mosquitoes weekly throughout the district including more than seven sites within the Oakdale area since April 1. West Nile virus has been identified in 12 mosquito pools (each pool or sample has 10-50 mosquitoes), the first mosquito sample that tested positive for WNV was collected on July 10, and the last one was collected on Aug. 13.
Dr. Wekesa shared, “The high temperatures, especially the night temperature above 68F that started in early July through Sept. 6 created a particular risk that increased transmission of this disease by mosquitoes.”
There have been several human cases of West Nile virus in the District and three cases in the Oakdale area, and two cases of WNV in horses.
“This has been a tough year for all of us and particularly residents of our county and surrounding counties,” Dr. Wekesa admitted.
In order to control mosquito infestations, it’s important to remove any standing water to avoid providing optimal breeding grounds.
“Mosquitoes require standing water to grow, if there is no standing water there are no mosquitoes. So, anything that people can do to reduce standing water to no more than three days will for sure improve our quality of life, greatly,” Dr. Wekesa said. “Because of our agriculture that heavily relies on irrigation water, such water often standing for weeks on end creates a major unnatural mosquito breeding source. The Mosquito Abatement Law gives the district the remedy of abating such property owners, abatement creates penalty on those properties producing mosquitoes. The remedy has never been used before, however as the District faces increasing challenges of protecting its residents such approach may become the viable, last resort option.”
Residents of the District pay taxes to provide abatement service. The East Side Mosquito Abatement District was established July 28, 1939 when agriculture and mosquito control faced different challenges. Currently, the District’s resources are adequate but lean. Prior to the pandemic hit, the District was in the process of requesting voters for a benefit assessment through balloting. Those plans were put on hold to such a time it will be conducive for such a request.
Due to the resource constraints, the District together with residents must work together to deter mosquito populations in their neighborhood. First, the irrigation districts and cities must be proactive in managing any leaks to water lines and repairing any ditches or drains as quickly as possible. Farmers can be considerate and take only water that is necessary during the irrigation cycle provided to them. Also, report standing water to the District, and talk to neighbors to reduce irrigation water to only what is necessary.
Individual residents can proactively remove containers, broken chairs, boats and other items that may hold water. Clean and maintain swimming pools, and similarly maintain sprinklers.
For more information on mosquito abatement or to report an infestation, call East Side Mosquito Abatement at (209) 522-4098.