Yellow Jackets

Swatting at a yellow jacket is never a good idea. 

Rather than chasing them off, you can easily cause them to give an alarm, triggering the attack of several hundred yellow jackets. So, who invited them to the picnic?

German wasp (Fir0002/Flagstaffotos) GFDL 1.2

Yellow jackets (or yellowjackets) are omnivorous social wasps and they can be a royal pain at outdoor summer events. Not only can yellow jackets be annoying, as they feed on your burgers and cupcakes, they can sting and bite at the same time! 

Unlike honey bees, which lose their stingers (and die) after a single sting, yellow jacket stingers do not have barbs and can be used repeatedly and with great prejudice. The more you know about yellow jackets, the better you can protect yourself and your family from painful stings.

Yellow jacket identification

Yellow jackets are frequently confused with bees and other wasps. Unlike stubby, brown honey bees, which are covered with short hairs, yellow jackets appear more smooth-bodied and shiny. Beneficial mud daubers have a very narrow waist and build their nests out of mud and paper wasps build small, umbrella-shaped nests with exposed cells. Mud daubers and paper wasps generally do not eat human food and are rarely aggressive unless provoked.
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Mud dauber (Didier Descouens) CC BY-SA 4.0

Paper wasp (Alvesgaspar) CC BY-SA 3.0

Aside from being unique in their high level of aggression, yellow jackets are generally medium-sized black wasps with jagged bands of yellow or white on the abdomen. While yellow jackets have the classic wasp-waist, it is often not clearly visible.

Western yellow jacket (Davefoc) CC BY-SA 3.0

Bald-faced hornet (Beatriz Moisset) CC BY-SA 4.0

​There are several different species of yellow jackets found in North America:

• bald-faced hornet (Dolichovespula maculata) - aerial nesting yellow jacket with white abdominal stripes; not actually a hornet 
• common aerial yellow jacket (D. arenaria) - aerial nesting; able to spray venom from their stingers 
• common yellow jacket (Vespidae alascensis) - commonly found at higher elevations, in rotted trees stumps; classified as V. vulgaris until 2010
• German yellow jacket - (V. germanica) - becoming more common in California, frequently nests in houses
• prairie yellow jacket (Vespula atropilosa) - ground-nesting; common to the western United States
• southern yellow jacket (Vespula squamosa) - aerial-nesting; found in eastern United States and Mexico
• western yellow jacket (Vespidae pensylvanica) - ground-nesting, also known as a “meat bee”

​You may be able to identify a yellow jacket from a distance by its tendency to fly side-to-side as it prepares to land. And if you ever see white grubs coming out of a wasp nest, it means that the adults have been unable to provide for their larvae, who are now in search for food on their own. Often, it is easier to identify a yellow jacket by its nest.

Yellow jacket nest (Phillip N. Cohen) CC BY-SA 4.0

Common aerial yellow jacket (Beatriz Moisset) CC BY-SA 4.0

Yellow jacket nests

Yellow jackets make their nests by scraping up wood fibers and mixing them with saliva. These nests look like fat, paper footballs when you can see them, but sometimes you can’t. 

Yellow jackets can be divided into ground-nesting and aerial nesting varieties. Aerial-nesting yellow jackets build the familiar rounded, hanging nests with a single entry hole at the base. While aerial-nesting wasps are generally not aggressive, they will attack if you get too close to their nest.

Ground-nesting yellow jackets, on the other hand, are extremely aggressive and you might not see them until it’s too late. Ground-nesting yellow jackets frequently build their nests in rodent burrows, rotted tree cavities, and houses. Apparently, to a yellow jacket, the space between the interior and exterior walls of your house make the perfect site for a nest that can contain up to 15,000 wasps. If you see a yellow jacket, it is safe to assume that there is a yellow jacket nest no more than 1/4 mile away.

Seasonal wasp aggression

Yellow jackets are particularly aggressive when it comes to protecting their nest. Yellow jackets are also likely to sting while out foraging for food. The aggressiveness of yellow jackets changes with the seasons.

In spring, yellow jackets are busy building their nest and providing larvae with protein, usually in the form of insects. As summer progresses and the colony population increases, their need for protein decreases and sugary foods, needed by the queen and her workers, are in greater demand. This is also when many resources start becoming more scarce and wasp aggressiveness becomes more of a problem.

By late summer and autumn, yellow jackets are best described as angry scavengers. This is when they end up at your picnics and cookouts. They are also seen around pet food, trash cans, and around fruit trees, where overripe fruit provides easy access to sugar.

​Preventing yellow jacket stings

If you are eating outside, the best way to prevent stings is to keep food and sugary drinks in sealed containers. This is especially true for canned soft drinks that contain sugar, as a wasp may go in the can and then sting your mouth when you take a drink. Once yellow jackets have found a food source, they will pester the area long after the food is gone. One popular method at reducing yellow jacket stings is to toss a piece of raw meat and a sugary food away from the area before unpacking the rest of the food. If yellow jackets discover this food source first, they may be less likely to become a problem at your picnic. I don’t know if it actually works, but it sounds good.

Working in the yard, one of the best ways to prevent stings is to be alert. Before digging, always look for ground-nesting wasps. I once was chased into my house by a swarm of very angry stinging insects when I tried to plant an apricot tree in my front yard. It is far better to be on the lookout before a confrontation occurs. If you do get stung, read my post on wasps for treatment tips.

Yellow jacket control

Lure traps placed around your property line are effective control measures against yellow jackets. You can buy yellow jacket lures at garden centers and many home improvement stores, as well as online. Most of these lures use a chemical called heptyl butyrate. This attractant works well on western yellow jackets, but not so well on other yellow jacket species. You can improve the effectiveness of yellow jacket lure traps by adding a small piece of raw meat to the trap. This will be especially effective on German yellow jackets. Just be sure to replace the meat frequently, as wasps are not attracted to rotting meat. Newer bait traps, those using esfenvalerate, have not been shown to be effective.

If you know the location of a yellow jacket nest, there are nest sprays that can kill the colony. Before you start spraying, you need to know that wasps will attack when they sense the poison being sprayed. While these poisons are effective, you should be sure to wear protective clothing and keep your distance while using the spray. Nighttime applications are significantly safer, but there is no guarantee. Plus, it may take a day or so for all the wasps to die and the remaining wasps are going to be very angry. 

Consider yourself warned.