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Everhart Park is one of the areas that is scheduled to be sprayed for mosquitoes.

After weeks of elevated mosquito levels and more confirmed West Nile Virus positives, the Chester County Health Department has scheduled a spray to take place on Thursday August 16 from 8 pm to 11:30 pm.

For the latest on the current spray including maps – go here.

The County considers spraying an action of last resort and while the chemicals used are EPA-approved, the agency’s website notes: “No pesticide should be regarded as 100 percent risk-free.”

Here’s what you need to know:

  • The county uses trucks equipped with a mounted sprayer to apply 0.66 ounces of EPA-approved DeltaGard per acre of land.
  • The spray that comes out of the truck is a fine mist that acts as a fogger in the area.
  • Spraying takes place in the evening when mosquitoes are their most active.  
  • The County uses DeltaGard to kill the adult insects. According to the DeltaGard website the chemical kills insects within 10 to 15 minutes and is effective at lower dosage rate than its competitors.
  • Insecticides used are only effective on adult mosquitoes. The CDC reports, these types of mosquito control programs will temporarily reduce mosquito populations in an area, but will not permanently get rid of them.  
  • In paperwork filed with the EPA, it states DeltaGard is extremely dangerous to fish and aquatic life.
  • To mitigate damages to aquatic life the County turns off sprayers near bodies of water.
  • The chemicals can also be hazardous to bee populations. If you maintain hives you are advised to take necessary precautions.

The government’s safety recommendations on spraying seem contradictory. At one time saying spraying is completely safe, but also suggesting taking cover indoors and closing windows is an option. The same advice is given for pets, “The spray does not harm pets, but you may choose to bring them inside when spraying occurs.”

What you can do to mitigate chemical exposure:

According to the County press release announcing the decision to spray, the chemicals become inactive a couple of hours after spraying.

  • So, while not required by the County or CDC it is recommended to keep pets and children indoors during the time of the spraying and probably a couple of hours afterward.  
  • After the spray rinse off any playground and patio equipment with water.
  • If you are experiencing any health problems, seek medical help.

What the critics say:

As of now the spraying is planned to go on as scheduled but that’s not to say everyone in the community is on board with the decision.

Critics site the danger of mass spraying chemicals, lack of research on the effects of exposure, the broad reach of the chemicals – they don’t just kill mosquitoes but a variety of other insects as well, including bees, butterflies, beneficial insects and natural predators of mosquitoes, and the overall effectiveness of spraying.  The spray only works on adult mosquitoes and not larva while at the same time killing the bugs’ natural predators. The result is temporary relief followed by a future spike.

The best way is to stop mosquitoes is prevention:

Be vigilant about dumping standing water. Check gutters, sump pumps and drains for clogs and backed up water. If you have an area of standing water that can’t be cleared look into treating it with a larvacide like BTI. BTI is available for free to borough residents. You can pick it up from the Public Works Department on Lacey Street.

Want more information on prevention? Visit the folks at the Don’t Spray Me organization who are doing all they can to avoid unnecessary chemical exposure or check out the county’s resources.

For more information on mosquito control sprays, call the the County Health Department at 610-344-6752.

Chester County residents can be notified about future mosquito control sprays through the following outlets:  Chester County Public Health Updates Sign up, Health Department Facebook or Health Department Twitter.

Worried West Chester’s not doing enough? Make your voice heard.


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