10 Tips on How to Respond to Today's Yellowjackets and Prevent Tomorrow's
It's a sunny late September afternoon and you head out to the patio to enjoy your lunch.

But, no sooner have you taken your first bite, when a yellowjacket appears. Then another, and another start circling your soft drink and your lunch. There goes your backyard meal plan, but why? Why are the yellowjackets so active right now and why are they attracted to my lunch?
Close up of a yellowjacket on a red flower
As ground-nesting yellowjacket queens prepare for winter, the workers search for food.
"It's the time of year when vegetation is dry and water is scarce, so, when worker yellowjackets are looking for food, they are attracted to whatever they can find. They can be drawn to sweet items such as honey, candy, fruit, and soft drinks; as well as red meat, chicken, fish, and even pet food. That means if you're having a meal, grilling burgers, or at a picnic outdoors and you have any of these food items, at this time of year, yellowjackets will find you," said District Operations Supervisor Terry Davis.

During late summer into early fall, the need to gather food, particularly proteins and carbs, intensifies for yellowjackets because they are raising males and new queens. Once the temperatures cool and the rest of the colony dies off, the new yellowjacket queens seek shelter until springtime when they emerge to create new colonies.

What Can You Do to Avoid Yellowjackets That are More Active, Right Now?

  1. Avoid eating or cooking meals outdoors if yellowjackets are present.
  2. Each evening, observe your yard for signs of yellowjacket nests.
  3. If you see any ground-nesting yellowjackets flying into a hole in the ground, or under shrubs, or into other vegetation, place something nearby to safely mark the location like a tool, hose, or small flag.
  4. Draw a simple map of your yard that shows where the potential nest is compared to the rest of the yard and tape the map to your front door or gate.
  5. Contact the District to request ground-nesting yellowjacket service.

During the District's ground-nesting yellowjacket service, a District employee will use the map and the marking to find the nest to inspect it. If it turns out to be a ground-nesting yellowjacket nest, the District employee can treat the nest. More information on the District's ground-nesting yellowjacket service guidelines can be found here.

Additional Recommendations to Reduce the Risk of Future Yellowjackets

  1. Tightly cover garbage containers
  2. Properly maintain compost piles
  3. Tightly cover can and bottle recycling bins
  4. Do not leave pet food outside
  5. Place pheromone traps outside and as far from doors and windows as possible in early spring to capture queens

Yellowjackets are considered to be beneficial insects because they eat garden pests and pollinate crops through daily foraging. However, these wasps will defend their nest if they sense a threat to the colony. Yellowjackets can sting and bite repeatedly which can be painful and may be life-threatening for individuals hypersensitive to wasp venom. The District provides ground-nesting yellowjacket service to reduce the risk of human harm from yellowjackets.
Contra Costa Mosquito & Vector Control District, an independent special district and public health agency, is located at 155 Mason Circle in Concord. Contact the District to report mosquito and vector problems online or at (925) 685-9301.