County to Hand-spray Nestor Neighborhood in Travel-related Zika Case

County Vector Control crews will hand-spray a neighborhood in Nestor this week to keep invasive Aedes mosquitoes from potentially spreading the Zika virus after mosquitoes were found near a person who contracted Zika outside the U.S.

County crews went through the neighborhood Monday, going door-to-door to notify people about the hand-spraying and to teach them how to keep mosquitoes from breeding inside and outside their homes.

County crews plan to hand-spray the area Wednesday, weather permitting.

The neighborhood is about nine acres in size, south of the Interstate 5-State Route 905 interchange and includes residences on Pikake Street, Deep Haven Lane, Lawndale Street and Quadra Avenue.


It will be the 10th neighborhood County Vector Control has had to hand-spray this year to protect the public health.

Two types of invasive Aedes mosquitoes that have been found in San Diego County can spread tropical diseases, including Zika, chikungunya and dengue, but only if they first bite an infected person. To date, no invasive Aedes mosquitoes have been found in San Diego County or California carrying any diseases.

County officials said even though the region is heading into winter months, people should continue to protect themselves from mosquitoes and take simple steps to keep them from breeding inside and outside their homes — mainly, finding and dumping out standing water where mosquitoes can breed.

The invasive Aedes mosquitoes that can transmit tropical diseases are particularly known for preferring to live and breed in urban areas next to people — in backyards, and even inside homes. They differ from the county’s native Culex mosquitoes — which can transmit West Nile virus if they first bite infected birds or animals.

One big difference is when they bite. Both species bite around dusk and dawn. But invasive Aedes bite during the day. Culex mosquitoes bite at night. To read about more differences between invasive Aedes and Culex mosquitoes, see our “Tale of the Tape.”

Trained County technicians will use ultra-low-volume backpack sprayers to apply Pyrenone 25-5, a pesticide approved for use by the Environmental Protection Agency. The product is made from chrysanthemums, poses low risks to people and pets and dissipates in roughly 20 to 30 minutes. However, the County is instructing residents in spray areas that they can avoid or minimize their exposure to the pesticide by taking simple steps:

  • Stay inside and bring pets indoors if possible
  • Close doors and windows, and turn off fans that bring outdoor air inside the home
  • Cover ornamental fishponds to avoid direct exposure
  • Rinse fruits and vegetables from your garden with water before cooking or eating
  • Wipe down or cover outdoor items such as toys and cover barbecue grills
  • Beekeepers and those with insects kept outdoors are encouraged to shelter hives and habitats during treatments. Beekeepers are required to register their apiaries with the County’s Department of Agriculture, Weights and Measures to receive advance notice of when a pesticide that may affect bees is applied to blossoming plants in their areas.
  • You may resume normal activities 30 minutes after the treatment

County officials reminded people to follow the County’s “Prevent, Protect, Report” guidelines.

Prevent mosquito breeding

Dump out or remove any item inside or outside of homes that can hold water, such as plant saucers, rain gutters, buckets, garbage cans, toys, old tires, and wheelbarrows. Mosquito fish, available for free by contacting the Vector Control Program, may be used to control mosquito breeding in backyard water sources such as unused swimming pools, ponds, fountains and horse troughs.

Protect yourself from mosquito bites

Protect yourself from mosquito-borne illnesses by wearing long sleeves and pants or use repellent when outdoors. Use insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, or IR3535. Make sure screens on windows and doors are in good condition and secured to keep insects out.

Report possible mosquito activity

Report if you are being bitten by mosquitoes during daylight hours, or if you find mosquitoes that match the description of Aedes mosquitoes by contacting the Vector Control Program at (858) 694-2888.

Information about the Zika viruschikungunya, and dengue can be found on the Centers for Disease Control and Prevention’s website.

For more information about mosquito-borne illnesses, go to San Diego County’s “Fight the Bite” website. You can also get more information about how the County works to trap and test invasive Aedes mosquitoes, and hear how the public can help prevent mosquitoes from breeding in the following videos.



Gig Conaughton is a communications specialist with the County of San Diego Communications Office. Contact