Were you bothered by yellowjackets last summer? Now is the time to get traps baited and placed outdoors. Overwintering western yellowjacket queens have been dormant all winter and are emerging now that spring is here, to feed and start a new nest. If you can capture the queen, you can prevent a new colony from forming.

There are two kinds of social wasps in our area that look somewhat alike—yellowjackets and paper wasps. Yellowjackets are the more problematic ones because their colonies can be much larger—there can be several thousand or up to fifteen thousand—and they vigorously defend their nests when disturbed. Their nests are usually underground in rodent burrows. These are the wasps that visit picnics and barbecues to scavenge meat and sugary foods.

Paper wasps are less defensive and rarely sting people. They build their paper nests in protected areas such as under house eaves. They can be a problem when the nest is over a doorway. The population in a nest is seldom over 100 wasps and is commonly only one or two dozen wasps.

Both yellowjackets and paper wasps provide a beneficial service by eating large numbers of pest insects. It is later in the summer when their colonies have grown larger and need more and more food that yellowjackets become scavengers, looking for whatever protein or sugar sources they can find. At this point, it is almost impossible to control their population. This is why it's so important to start the control process before you start to see yellowjackets flying around your picnic.

You can purchase yellowjacket traps at hardware stores or nurseries. These yellow plastic traps have a chemical attractant that lures yellowjackets into the trap. Follow package directions carefully. Make sure you don't get the attractant on your hands when you are setting it up to avoid attracting yellowjackets to your hands.

What to do if you find a nest on your property? Contra Costa Mosquito and Vector Control will treat ground-nesting yellowjackets at no charge. Contact them at 925-685-9301 or https://www.contracostamosquito.com/request-services For above-ground nests, you should call a licensed pest control company.

For more information on controlling yellowjackets and other social wasps, see this link: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7450.html
Quick Tips: https://ipm.ucanr.edu/QT/yellowjacketscard.html

Help Desk of the UC Master Gardeners of Contra Costa County (SEH)

Yellowjacket (notice the black antennae)

paper wasp (notice the yellow antennae)

Yellowjacket lure trap (photo by Susan Heckly)