Why Yellowjackets Suddenly Seem To Be Everywhere in Late Summer

They did not arrive overnight. Their colonies have been growing since spring—and by late summer, thousands of hungry workers may be searching for their next meal.

You are pouring lemonade on the patio when one appears. Then another begins circling the picnic table. Before long, yellowjackets are inspecting the soda cans, hovering over the fruit bowl and taking an uncomfortable interest in whatever is coming off the grill.

If yellowjackets suddenly seem to be everywhere in late summer and early fall, you are not imagining it. This is the time of year when their colonies reach their greatest size. More workers are flying, natural food supplies are changing, and some yellowjacket species become persistent scavengers around the foods people enjoy outdoors.

Here is why yellowjacket activity increases as summer winds down, how to keep them away from an outdoor meal and when a nest requires professional attention.

Why Are There So Many Yellowjackets Right Now?

A yellowjacket colony begins modestly. In spring, a queen that survived the winter emerges from shelter, selects a nesting site and starts raising the first generation of workers. Those workers then take over food gathering, nest construction and care of the developing young while the queen continues laying eggs.

The colony grows throughout summer. By late summer, a nest may contain hundreds or even thousands of yellowjackets. The University of Minnesota Extension reports that some nests can hold approximately 5,000 wasps at their seasonal peak.

That population boom is the biggest reason yellowjackets become so noticeable in August and September. A nest that produced relatively little visible activity in June can send out a large workforce by the end of summer.

Quick answer: Yellowjackets seem more numerous in late summer because their annual colonies are at or near peak population. Some species also actively scavenge around ripe fruit, garbage, meat and sweet drinks, bringing them into frequent contact with people.

Why Do Yellowjackets Invade Picnics and Cookouts?

Yellowjackets are opportunistic foragers. They capture insects and spiders to feed their developing young, which makes them useful predators of caterpillars, flies and other garden pests. Adult yellowjackets also seek carbohydrates from nectar, honeydew and the juices of ripe or overripe fruit.

Human food offers an easy substitute. Depending on the species and its needs, a yellowjacket may investigate:

• Soda, lemonade and fruit juice
• Ripe or fallen fruit
• Frosting, candy and desserts
• Meat, fish and pet food
• Open garbage or recycling containers
• Grease and food scraps around grills
• Spilled hummingbird-feeder solution
• Water during hot or dry weather

By late summer, there are simply more workers available to find these concentrated food sources. Once a reliable source is discovered, repeated visits can make a patio, orchard or trash area seem overrun.

Are Yellowjackets More Aggressive in Fall?

Some species can become more aggressive while scavenging in late summer and fall, according to the University of Minnesota Extension’s seasonal pest guidance. But “aggressive” does not mean every yellowjacket is looking for someone to sting.

Most dangerous encounters occur in two situations:

1. A person disturbs a nest. Yellowjackets vigorously defend their colony, particularly when someone steps near an underground entrance, runs a mower over it or moves an object concealing the nest.
2. A foraging yellowjacket is trapped or swatted. A wasp crawling inside a drink can, caught in clothing or struck by a hand is much more likely to sting.

Unlike a honey bee, a yellowjacket does not normally leave its stinger behind. It can therefore sting more than once.

The safest response to a single yellowjacket is usually to remain calm and move slowly. Frantic swatting increases the likelihood of provoking it. If several yellowjackets are repeatedly entering and leaving one spot in the ground, a wall or a woodpile, back away: you may have found the nest entrance.

Yellowjacket or Honey Bee? How To Tell the Difference

Yellowjackets are wasps, not bees. The distinction matters because their behavior, nesting habits and value to the garden differ.

Yellowjackets usually have bright black-and-yellow markings, a shiny body with relatively little hair and a compact waist. Many species nest in old rodent burrows, hollow logs, landscape timbers, wall voids or other enclosed cavities.

Honey bees are generally golden-brown and noticeably fuzzy. They collect pollen and nectar from flowers and are less likely to investigate a hamburger or soda. Honey bees also leave a barbed stinger behind when they sting; yellowjackets do not.

Paper wasps have longer, more slender bodies and legs that often dangle during flight. Their open-celled paper nests are commonly built beneath eaves and other sheltered horizontal surfaces.

Correct identification can prevent beneficial pollinators from being needlessly harmed. If you are uncertain, take a photograph from a safe distance and contact a local Cooperative Extension office or pest-management professional.

How To Keep Yellowjackets Away From Outdoor Food

There is no dependable spray that simply repels every scavenging yellowjacket from a yard. Removing the attractions is usually the most effective first step.

Before your next cookout:

• Keep serving dishes covered until everyone is ready to eat.
• Use cups with lids and avoid drinking directly from an unattended can.
• Check straws, glasses and cans before taking a sip.
• Wipe up sweet spills immediately.
• Put leftovers away as soon as the meal ends.
• Keep garbage in a container with a tight-fitting lid.
• Rinse sticky bottles and cans before placing them in recycling.
• Clean grease and food scraps from the grill.
• Do not leave pet food outdoors.
• Pick up fallen apples, pears, peaches and other fruit before it ferments.
• Wear shoes when walking through lawns where hidden ground nests may be present.

If one yellowjacket lands on the table, give it space to leave or gently brush it away with an object. Do not slap at it with your hand.

Traps may catch some yellowjackets, but they rarely eliminate an established colony and may attract wasps toward the area where they are placed. If you use one, position it well away from doors, seating areas, play spaces and outdoor dining tables.

For additional prevention and control options, see our guide to natural ways to deter wasps safely.

Where Do Yellowjackets Build Their Nests?

Many yellowjacket nests are difficult to see because they are underground or inside a protected cavity. Common locations include:

• Abandoned rodent burrows
• Gaps beneath landscape timbers
• Hollow logs and tree cavities
• Stone walls
• Woodpiles
• Sheds and outbuildings
• Attics and wall voids
• Openings around siding or utility penetrations

A small, steady stream of yellowjackets flying to and from the same opening is a strong sign of an active nest. Do not block that opening. Sealing wasps inside a wall can drive them to find another exit—sometimes into the house.

Should You Remove a Yellowjacket Nest?

Not every nest needs to be destroyed. Yellowjackets prey on many insects people consider garden pests, and an out-of-the-way colony will naturally die when sustained freezing weather arrives in cold-winter regions.

Leaving a nest alone may be reasonable when it is far from people, pets, paths and buildings. Professional control is the safer choice when:

• The nest is beside a doorway, walkway, patio, mailbox or play area.
• Yellowjackets are nesting inside a wall, attic or other structure.
• The nest is large, concealed or difficult to reach.
• Anyone in the household has a known allergy to insect venom.
• Repeated stings are likely because the area cannot be avoided.

Never pour gasoline or another flammable liquid into a ground nest, and never attempt to burn it. These methods can cause fire, soil contamination, serious injury and an attack by the colony. Follow the label exactly if using any registered pesticide, or hire a licensed pest-management professional.

When Will Yellowjackets Go Away?

Yellowjacket colonies are annual. As summer ends, the colony produces new queens and males. After mating, the new queens leave to find protected places where they can spend the winter.

The old queen and workers remain active until freezing temperatures kill them. In colder climates, activity often drops sharply after the first hard freeze. You can check your area’s typical timing with the Farmers’ Almanac average first frost dates chart.

Only the newly mated queens ordinarily survive to begin new colonies the following spring. The old nest is generally not reused.

In warm climates, the timing can be less predictable, and yellowjackets may remain active much later into the year.

What To Do If You Are Stung

For an ordinary local reaction, move away from the area to prevent additional stings, wash the site with soap and water and apply a cold compress to reduce discomfort and swelling. Because yellowjackets usually do not leave a stinger behind, there is generally nothing to scrape out.

Watch closely for symptoms away from the sting site. Difficulty breathing, swelling of the throat or tongue, widespread hives, dizziness, fainting, vomiting or a rapid decline may indicate anaphylaxis. The American Academy of Allergy, Asthma & Immunology advises using prescribed epinephrine immediately and seeking emergency medical treatment for a severe reaction.

Call 911 for signs of anaphylaxis. Multiple stings, a sting inside the mouth or throat, or rapidly worsening symptoms also warrant urgent medical attention.

Yellowjackets Are Annoying—but They Have a Job

It is difficult to appreciate a yellowjacket hovering over your lunch, but these wasps are not merely picnic pests. During much of the growing season, they capture caterpillars, flies and other insects to feed their larvae. In the right place, they are part of the garden’s natural pest-control crew.

The sensible goal is not to eliminate every yellowjacket. It is to reduce the food sources drawing them toward people, recognize possible nest entrances and treat high-risk colonies with appropriate caution.

For a few late-summer weeks, keep the fruit picked up, the lemonade covered and the trash can tightly closed. The first hard freeze will eventually end most colonies—but until then, a little awareness can make outdoor meals considerably more peaceful.

Frequently Asked Questions

Why are yellowjackets so bad in August and September?

Their colonies have been growing since spring and typically reach peak population in late summer. Large numbers of workers are then searching for food and water, including ripe fruit, garbage and food served outdoors.

Why are yellowjackets attracted to soda?

Adult yellowjackets consume sugary foods. Soda, juice, desserts and overripe fruit provide concentrated carbohydrates that are easy for them to locate.

Do yellowjackets die in winter?

In cold-winter regions, the old queen and workers die after freezing weather arrives. Newly mated queens survive in protected shelters and establish new colonies in spring.

Will yellowjackets reuse an old nest?

Generally, no. Their nests are annual and are normally abandoned after the colony dies.

Can yellowjackets sting more than once?

Yes. Their stingers are not barbed like those of honey bees, so they can withdraw the stinger and sting repeatedly.

Should I swat a yellowjacket near my food?

No. Stay calm, move slowly and allow it to leave. Swatting or trapping the insect against your skin increases the chance of a sting.