The city has had mosquito traps tests positive through the month of July.
The Tarrant County Public Health Department, which conducts the weekly tests, notified the city of positive results on July 2, 9, 16 and 23.
Neither Grapevine nor Southlake have experienced positive tests this season.
The positive traps in Colleyville were found on the first week of July near Sparger Park in southeast Colleyville.
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The second positive trap was reported the next week near Windermere Court in the central, southeast part of town. The third and fourth positive results occurred at the site near Windermere Court.
Colleyvile has has responded by treating the sites with larvicide and plans to continue treatment through the season, and notified residents within a quarter-mile area of the positive result.
City engineer Jeremy Hutt said the only time the city would engage in ground pesticide spraying is if there is a human case in the city.
Colleyville has three mosquito traps that stay in the same locations and two traps it rotates at 16 different sites. The three stagnant traps are near Big Bear Creek, Little Bear Creek and the Colleyville Nature Center.
Last year, the city reported only one positive trap.
Residents can obtain two larvicide briquettes from the city’s Public Works/Engineering office at City Hall. The city also encourages residents to drain standing water, wear long sleeves outdoors, using insect repelent with DEET and avoiding going outdoors at dawn and dusk.
Trophy Club began distributing two free mosquito larvicide briquettes to each household on April 22, Public Information Officer April Reiling, said.
“Larvicide briquettes help with source reduction, which means when placed in standing water pools, the briquettes kill mosquito larvae before they can hatch,” she said.
Reiling said Code Enforcement and the Parks Department are working together to treat known water pools in Trophy Club, “but staff also relies on the residents to make sure potential breeding sites, especially located on private property, are removed or treated.”
In Grapevine, residents can obtain free mosquito “dunks” that are placed in water that cannot be drained for free, limit two per month. Those interested can pick them up at the Parks and Recreatoin Administration Department at City Hall or at the Municipal Service Center.
Environmental Services Specialist Oleksandra Bikman in Keller said the “mosquito abatement program is very effective, but July is traditionally the peak of mosquito season, so every city is seeing a high number of mosquitos right now.”
“We’ve yet to have any mosquito pools in Keller test positive for West Nile Virus, but we continue to trap at five sites each week for testing by the county and spend a lot of time out in the field monitoring and treating sites with a potential for mosquito breeding — both natural and manmade,” Bikman said.
She said that since 2012, cities have been more agressive in mosquito abatement efforts. That is when there were a record West Nile Virus outbreaks throughout the state, Bickman said.
Residents have stepped up doing their part by checking checking yards for standing water. Bickman said rain gutters, and any vegetation being watered often such as shrubs, flowers and potted plant sare at a higher risk.
“They should also check any French drains on their property, make sure outdoor living areas, toys and kiddie pools aren’t holding water, and mow their lawn regularly so they can be sure irrigation is absorbing into the soil completely,” Bickman said.
The city offers environmentally friendly mosquito dunks at Keller Town Hall on a first-come, first-served basis.
Since May, Roanoke has been spraying for mosquitos on the first Thursday of the month. The spraying will continue through October.
-Marty Sabota contributed to this report.