Why Are Yellow Jackets So Aggressive in Late Summer?
Every year around Labor Day, outdoor lunches on the South Coast get crowded. Yellow jackets circle the hot dogs, crawl into soda cans and follow you to the trash barrel. They weren’t doing this in June. Something changed in their colonies, and it has to do with sugar.
Quick answer: Yellow jackets get aggressive in late summer because their colonies are at peak size just as their food supply shifts. All summer, workers hunt insects for the larvae and get a sugary liquid from the larvae in return. In late summer the queen stops producing workers, larvae dwindle, and thousands of hungry workers go looking for sugar: soda, fruit, trash and picnics. The first hard freeze ends most colonies.
What happens inside a yellow jacket nest in late summer?
A yellow jacket colony lives for just one season. In spring, a single queen that survived the winter builds a small paper nest, often in an old rodent burrow underground or in a wall void, and raises her first workers alone. Through the summer the colony grows. Clemson Cooperative Extension says a colony may reach several hundred workers by August, and some nests hold thousands.
All summer, workers hunt caterpillars, flies and other insects, chew them up and feed them to the larvae. In return, the larvae give the workers a droplet of sugary liquid. That trade keeps the adults fueled.
By late summer the colony switches to raising next year’s queens and males, and stops making new workers. With fewer larvae to feed, the workers lose their sugar supply at the same moment the colony is at its biggest. Meanwhile, flowers and natural sugar sources are thinning out. The result is a large, hungry workforce looking for carbohydrates anywhere it can find them.
Are yellow jackets really more aggressive in fall?
They’re more persistent, and there are more of them. A yellow jacket hunting for sugar will keep coming back to your drink no matter how many times you wave it off. Near the nest, they also defend more fiercely: a big colony has a lot to protect, and its guards respond fast to vibration, like a lawn mower passing over an underground entrance. Unlike honeybees, yellow jackets have a smooth stinger and can sting again and again.
That’s why most “bee stings” in September aren’t from bees at all. Our guide to honeybees vs. wasps vs. yellow jackets shows how to tell them apart.
How do you avoid yellow jacket stings outdoors?
Take away the sugar and the surprises:
- Cover food and drinks. Use lids and straws, and look before you sip from a can.
- Clean up fast. Clear plates, wipe spills and pick up fallen fruit under apple and pear trees.
- Keep trash tight. Use lidded barrels and empty them often.
- Don’t swat. Swatting near the nest invites more stings. Move away calmly instead.
- Watch where you mow. Before cutting the lawn or trimming hedges in August, look for a steady stream of wasps going in and out of one hole in the ground. (Lots of separate small holes with one bee each are harmless ground bees.)
- Put traps away from people. Commercial yellow jacket traps work best set at the edges of the yard, so they pull wasps away from where you sit, not toward it.
Do yellow jackets bother honeybees?
Yes, and beekeepers watch for it every fall. Clemson notes that yellow jackets rob honey from beehives and can stress weak colonies. In September, you’ll see them hovering at hive entrances, picking off returning honeybees or slipping inside for honey. Beekeepers respond by narrowing hive entrances so the guard bees can defend them.
If you set out traps, avoid sweet baits like juice or jam during the day, which also lure honeybees. Clemson suggests meat baits, such as raw bologna, which yellow jackets like and honeybees ignore.
What should you do about a yellow jacket nest?
If it’s somewhere nobody walks, leave it. The colony dies off with the cold, and nests aren’t reused. If the entrance is by a door, a path or a play area, call a pest control professional; treatment is usually done at night, when the wasps are inside. Never pour gasoline into a nest or block the entrance of a wall nest, which can drive the wasps indoors. If it’s honeybees in the wall, see bees in your wall or chimney. We collect honeybee swarms but don’t remove wasps.
When do yellow jackets go away?
With the first hard freeze. Clemson Cooperative Extension says “the first hard freeze will eliminate most colonies.” The workers, males and old queen all die. Only newly mated queens survive, tucked under bark or in leaf litter, to start fresh colonies in spring. On the South Coast, that usually means yellow jacket trouble fades by late October or November.
Frequently asked questions
Are yellow jackets bees?
No. Yellow jackets are wasps. They have smooth, shiny bodies with bright yellow and black markings, eat insects and sugar, and don’t make honey. Honeybees are fuzzy, golden-brown and gentle away from their hive.
Why do yellow jackets like soda so much?
Late in the season, yellow jacket workers stop getting sugar from the larvae they feed, and natural sources are scarce. Sweet drinks are concentrated, easy sugar. Cans are a common hiding spot, so check before you drink.
Can a yellow jacket sting more than once?
Yes. Their stinger is smooth, so they can sting repeatedly without dying. A honeybee’s barbed stinger catches in skin, so it stings once and dies. For first aid and allergy warning signs, see our bee sting guide.
Do yellow jackets reuse their nests?
No. Each nest is used for one season. In spring, new queens build new nests, often in a different spot, so an old empty nest can be left alone or removed after a hard freeze.
Are yellow jackets good for anything?
Yes. Through most of the summer they hunt caterpillars, flies and other insects, which helps gardens and farms. They only become a nuisance at the end of the season, when they turn to sugar.
Sources
- Clemson Cooperative Extension, Home & Garden Information Center, “Yellow Jackets” fact sheet.
A few careful habits get you through the last warm weeks of the year. After the first frost, the patio is yours again.