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Mosquito Populations Spur Spraying,
Continued Vigilance for West Nile Virus in Western Riverside County

County of Riverside Environmental Health logo

Spraying is scheduled next week in two areas of western Riverside County to reduce mosquito populations, as the county vector-control staff continues to find mosquitos that test positive for West Nile virus.

In Murrieta, mosquitos at Monroe Basin tested positive for the virus. Due to the high number of mosquitos trapped, the Riverside County Vector Control Program staff has scheduled ultra-low volume ground applications of Zenivex, using truck-mounted sprayers to reduce the number of adult mosquitos. The basin covers 36 acres and the treatment area is bordered by Jackson Avenue to the north and Monroe Avenue to the southwest.

Application of Zenivex, a mosquito-control product approved by the Environmental Protection Agency (EPA Reg No 2724-807), is scheduled for Wednesday (9/20) from 7 p.m. to 9 p.m. Signs will be posted along the route Monday (9/18) informing residents of the control efforts.

Although there have been no recent positive tests for the virus, Zenivex also will be sprayed as a precaution to reduce a high number of mosquitos in an area of Nuevo. The treatment will cover 3.5 miles starting at Davis Road, south. The perimeter of Mystic Field will be treated then continuing on Reservoir Avenue to Tenth Street, Lakeview Avenue back to Reservoir Ave. The application is scheduled for Tuesday (9/19) from 5 a.m. to 7 a.m. Signs will be posted along the route today (9/15) informing residents of the control efforts.

A very small number of mosquitos also tested positive for West Nile virus last week in Moreno Valley near Heacock Street and Parkland Avenue. The county vector control staff will respond by placing more traps in the area, conducting follow-up testing and reaching out to residents to ensure they understand how to prevent mosquito breeding in their yards. Spraying has not been scheduled because such an extremely low number of mosquitos was trapped.

Zenivex is registered by the EPA for use in controlling mosquitos and protecting public health. It is applied according to label instructions by trained and certified technicians. Although the product poses very low to no risk, some people may prefer to avoid exposure. For those who wish to minimize exposure, residents and pets should remain indoors and keep windows closed during and for 15 minutes following ground application. The amount of material sprayed is three ounces per acre, which ensures that humans, animals and crops are safe.

The vector-control staff follows a pest management protocol that includes, intensifying mosquito surveillance, searching out breeding sites, conducting larval control where appropriate, and educating property owners about how to prevent mosquito breeding on their property.

To protect yourself from mosquito bites:

  • Apply Insect Repellent. Use a repellent with DEET (N, N-diethyl-m-toluamide), picaridin (KBR 3023), oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] or IR3535 according to the instructions on the product label. DEET products should not be used on infants under two months of age and should be used in concentrations of 30 percent or less on older children. Lemon eucalyptus oil should not be used on children under three years of age.
  • Be Aware of Peak Mosquito Hours. Dawn and dusk are peak biting times for many mosquitos. If mosquitos are biting you during the daytime hours, please mention that when you call our office because it might help identify the species of mosquito in your area.
  • Clothing Can Help Reduce Mosquito Bites. Wear long-sleeves, long pants, and socks when outdoors to help keep mosquitos away from skin.
  • Mosquito-Proof Your Home. Drain Standing Water. Mosquitos lay their eggs in standing water. Limit the number of places for mosquitos to breed by draining/discarding items that hold water. Check rain gutters and drains. Empty and scrub out any unused flowerpots and wading pools. Change water in birdbaths, livestock troughs and pet bowls at least weekly, scrubbing thoroughly before refilling.
  • Install or Repair Screens. Keep mosquitos outside by having tightly fitting screens on all of your windows and doors.

Please call the vector control office at 951-766-9454 if you have any questions, would like to report a mosquito problem in your area or to request mosquito larvae-eating fish. You may also visit our website or Facebook page for more information. in Moreno Valley.

Editor’s note: the maps below this release show the areas in Nuevo and Murrieta scheduled for treatments by the county vector-control staff.


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Upon request, this news release will be made available in appropriate alternative formats to persons with disabilities, in compliance with the Americans with Disabilities Act of 1990. Any person with a disability who requires a modification or accommodation in order to participate in this meeting should direct such requests to, ADA Coordinator, at 951.413.3045 at least 72 hours before the meeting. The 72-hour notification will enable the City to make reasonable arrangements to ensure accessibility to this meeting.