Warning: spray in the air August 28! (Was to be Aug. 25)


Update: this spraying was postponed from Aug. 25 due to adverse conditions then.

The Chesco Health Dept., which for 3 years has been tending to important missions like reducing the death toll from Covid, has returned to its old futile habit of trying to kill mosquitoes on the wing (those that happen to be sheltered in an unexposed place like brush or a crack in tree bark escape the spray). It plans to spray a large residential area of West Goshen, East Goshen and Westtown on the evening of August 25.

As is pretty obvious, any chemical toxin able to kill one adult insect is going to kill or adversely affect other insects, and isn’t great for other organisms either. The excuse used is always West Nile Virus, which so far this year has been fatal to about 1 in 60 million Americans, almost entirely in the South. (Compare to Covid, which so far this year has killed about 1 in 1,615 Americans; would you rather the County use public resources on WNV or Covid?) The Health Department does not have a mandate to adjust the environment to people’s liking!

How would you even know spraying is imminent in your neighborhood? The Health Department is supposed to post notices in the affected area and one would hope municipalities would relay the information to their residents. However, experience shows that most people remain unaware and we have even seen joggers obliviously inhaling recently sprayed air.

What can you do both to protect yourself and to monitor what is happening? See more here. In particular, if you are in the spray area, stay inside, close windows and avoid air conditioners drawing in outside air.

See the County’s press release below. What does “where multiple mosquito samples have tested positive for WNV” mean? It means that in more than one mosquito trap in some area, one or more mosquitoes were carrying the WNV virus. The trap could contain a dozen or a thousand mosquitoes, it makes no difference to whether the trap testis positive.

Note particularly the sentence “After exhausting other available mosquito control strategies, treatment is conducted to reduce residents’ risk of WNV infection.” What would “exhausting other strategies” look like?

• Conducting regular larviciding of suspect bodies of water (it’s much easier to kill larvae because they can’t fly away).

• Working closely with municipalities to educate Public Works staff, encourage residents to help control mosquitoes, and widely distribute larvicide to residents and businesses.

Please let us know if you have or have not seen such strategies in action where you live.

Mosquito Control Treatment Scheduled for Parts of West Goshen,
East Goshen, and Westtown Townships to Prevent West Nile Virus

WEST CHESTER, PA – August 23, 2022 – The Chester County Health Department will conduct a mosquito control treatment spray in portions of West Goshen, East Goshen and Westtown Townships on Thursday, August 25th from 8:00 pm to 11:00 pm. The need to conduct the control treatment follows confirmation of multiple mosquito samples that tested positive for West Nile Virus (WNV) in the area. The rain date is Monday, August 29th from 8:00pm to 11:00pm.

A map of the area where the mosquito control treatment will occur is below.

The Chester County Health Department conducts mosquito control treatment in areas with high levels of mosquito activity and where multiple mosquito samples have tested positive for WNV. After exhausting other available mosquito control strategies, treatment is conducted to reduce residents’ risk of WNV infection. Anyone living in an area where mosquitoes are infected with WNV is at risk, but the risk of infection is highest for people who work outside or participate in outdoor activities. Less than one percent of people infected may develop serious illness. While serious illness can occur in people of any age, people over 60 years of age, people who have received organ transplants, and people with certain medical conditions such as cancer, diabetes, hypertension, and kidney disease are at greatest risk for serious illness.

The Chester County Health Department uses a truck-mounted sprayer to apply 3.0 ounces of U.S. Environmental Protection Agency-approved product (Zenivex E4 RTU) per acre of land. The mosquito control treatment becomes inactive in just a few hours, or with sunshine. Treatments are conducted after sunset, when mosquitoes are most active, and bees have returned to their hives. Sprayers are turned off near bodies of water and apiaries to protect aquatic life and bees.


The Chester County Health Department notifies registered beekeepers and residents who are listed as hypersensitive in a designated treatment area prior to conducting a treatment. People who are concerned about exposure to mosquito control products can reduce their potential for exposure by staying indoors with children and pets when their neighborhood is being treated. If you would like to take extra precautions after the treatment is completed, you can rinse off outdoor furniture or playground equipment before use.

While these types of treatments help reduce mosquito populations, the Chester County Health Department encourages residents to take action on their own property to make it a “Bite-Free Zone.” For additional information, visit www.chesco.org/3624/Mosquito-Borne-Diseases.

# # #

The Chester County Health Department is a member of the Environmental Protection Agency’s Pesticide Environmental Stewardship Program. This program requires participants to affirm that environmental stewardship is an integral part of their integrated pest management (IPM) practice, use current, comprehensive information regarding the life cycle of mosquitoes within their IPM program, educate the community on the benefits of IPM, and demonstrate a commitment to pesticide risk reduction activities.

Map of Mosquito Treatment Area

For further information please contact Rebecca Brain, Chester County Public Information Office at 484-798-8710, or Maria Marabito, Chester County Health Department Communications Coordinator at mmarabito@chesco.org.

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