June brought a bumper crop of mosquitoes to West Side communities.
Those who work to keep the mosquito populations in check are hopeful that a combination of falling river levels and their combined eradication efforts will better curb the insects in July.
Residents of Newman, Gustine and surrounding areas are among those who have been impacted by higher-than-normal mosquito populations through the early summer, said David Heft, general manager of the Turlock Mosquito Abatement District, and Rhiannon Jones, general manager of the Merced County Mosquito Abatement District.
Heft and Jones each attributed high river levels - and the standing water left behind when the rivers recede - as being key contributors to the abundance of mosquitoes.
“We have been out there via ground and aerial applications, but it seems to only make a dent,” Jones commented. “Our pilot says that from the air, the water conditions look worse than when we were asking for FEMA funding in 2017 during the flooding.”
Jones said that the Merced County district has been using ground-based spray units to treat in Gustine, while conducting aerial applications over rural areas. Aircraft will be used to spray cities only if vector-born diseases such as West Nile Virus are detected, she noted.
Heft said the early season has been challenging on the West Side of Stanislaus County as well.
While the nearby river levels have receded, Heft told Mattos Newspapers, they have left behind mosquito-prone areas encompassing thousands of acres of land in Merced and Stanislaus counties.
“That is what we have been dealing with for the last month and a half,” Heft commented. “Usually when we have river flooding, it is gone by June. This is unique in that we have flooding and we are coming into July. The high numbers of acreage flooded and the warmer temperatures have created a perfect storm (for mosquito reproduction).”
The good news, Heft said, is that mosquito populations are coming down.
Heft said the Turlock district plans to begin aerial missions this week, coinciding with the start of its fiscal year, in combination with ground-based spraying.
“Our trapping has shown that mosquito levels have gone down tremendously. I think that after we get the airplane things should be back to normal,” he commented. “That is dependent on river levels staying low. If they do a big release of water, that is going to flood everything again and we are going to be back to square one.”
The mosquitoes which have been plaguing the West Side through early summer have been of the Aedes variety, Heft noted.
Those mosquitoes do not tend to carry viruses such as West Nile, he explained, but are active in the daytime and are aggressive biters.
“A lot of the mosquitoes that people have been having problems with are the Aedes. Those mosquitoes, when they are active, generate a lot of calls,” Heft explained.
As summer progresses, Jones and Heft said, the threat of West Nile Virus becomes a greater concern.
Jones said temperatures in excess of 90 degrees speeds up the reproductive cycles of mosquitoes, which can go from egg to adult in less than five days, and also amplifies virus activity.
Jones reported Monday that a mosquito sample collected in the Winton area has tested positive for West Nile. That is the first detection of the virus in Merced County this year.
Mosquitoes of the Culex variety are those which carry the virus and would be more common than the Aedes in a typical year, Heft added. Those mosquitoes are usually more active at dawn and dusk.
“(Aedes) have dropped way down. Our concern now is more the Culex mosquitoes,” he explained.
Residents play a crucial role in containing mosquito populations by eliminating standing water in which mosquitoes can breed, Heft and Jones emphasized.
People are also cautioned to avoid being outside at dawn and dusk, use repellent containing an approved active ingredient such as DEET, and wear protective clothing if outside when mosquitoes are active.
Residents may track scheduled spraying applications and submit service requests through the websites of their respective abatement district.
The participation of the public in eliminating breeding sources and reporting mosquito problems is essential to the efforts of the abatement districts to keep the insects in check, Jones emphasized.
The Turlock Mosquito Abatement District may be reached at 634-1234. The Merced County Abatement District may be reached at 722-1527.