Yellowjackets in Ohio and California. What to Do About Them

Yellowjackets are 1/2 to 1 inch long with bright yellow and black bands and a very short, narrow waist.¹ Ohio State describes workers at about 1/2 inch and queens at about 3/4 inch, with hard, shiny, mostly hairless bodies.²

That separates them from honey bees, which are hairier and less brightly striped.¹ Paper wasps are slimmer, with long legs and a thin waist.¹ The bald-faced hornet is a black and white relative that builds an open nest.³

Look at the nest too. A yellowjacket nest is wood fiber and saliva, closed on every side except a small opening at the bottom, and it can have 10 or more tiers of combs inside.² Compare the photos above, and see the main wasp guide for the other look-alikes.

One fertilized queen survives the winter in a protected spot and comes out in April and early May in Ohio.² She feeds her first larvae for about 18 to 20 days, and they become workers.² In California queens appear from late winter to early spring.¹

Workers hunt other insects for protein through spring and midsummer.¹ Colonies reach about 4,000 to 5,000 workers and 10,000 to 15,000 cells by August and late September in Ohio.² UC IPM says colonies can reach between 1,500 and 15,000 wasps, depending on species.¹

The last generation is new queens and males. When cold weather arrives, the old queen, the workers and the males die.² In very mild winters and coastal areas south of San Francisco, some California colonies last several years.¹

• A steady line of wasps going into one hole in the lawn, a mulch bed or a rotted stump.²
• Wasps going in and out of a crack in siding, a soffit or a gap near a window. Wall and ceiling voids are common nest sites.²
• A gray paper nest with a small opening at the bottom, hanging from an eave or branch.¹
• Wasps swarming around pop cans, trash and pet food from August to October.²
• A scratching or buzzing sound in a wall, or wasps showing up inside the house.²

Ground nests often start in an abandoned mammal burrow.³ Walk the yard with your eyes on the ground, not your hands.

Yellowjackets sting mostly to defend the nest, but they will also sting when trapped or squeezed.² The stinger has no barbs, so a single wasp can sting repeatedly, especially inside clothing.¹

Many stings can hurt the kidneys, because venom enzymes and tissue debris can block them.¹ One to two people in 1,000 are allergic to bee or wasp stings.⁴ Watch for hives, dizziness, trouble breathing or a swollen throat.⁴

Ohio State says use an ice pack in 10 minute rounds and take an antihistamine.² Go to the emergency room if you had a past allergic reaction, have trouble breathing or swallowing, or feel confused or faint.² See a doctor if you were stung more than 10 times or in the mouth or around the eyes.²

Do not squash a wasp near you. It sends out an alarm scent that draws more of them.²

Ohio State strongly recommends a professional to kill and remove the nest.² A nest underground or in a wall is the worst kind to try alone. UC IPM says underground nests may reach well past the visible hole, and agitated wasps may be around the next day.¹

What a pro does is simple. For a ground nest, puff insecticidal dust into the entrance at sunrise. For a wall void, run an aerosol wand in for 10 to 30 seconds and leave the opening unplugged.² Treating at dawn works because wasps are sluggish.²

Traps help with the numbers, not the nest. Lure traps with heptyl butyrate attract mainly western yellowjackets.¹ Most commercial traps do not attract German yellowjackets.² Poison bait stations are gone from the market.¹

Ask for the species found, the product used, and whether a re-treatment is included if wasps return.

One national guide averages $725 for yellowjacket removal, the highest of any wasp it lists. Paper wasps average $385 and hornets $450.⁵ The reason is the nest. Yellowjackets nest underground, which costs more.⁵

Where the nest sits moves the price. Low outdoor nests average about $300. Attic nests run $325 to $450, wall nests $350 to $875 and chimney nests $475 to $600.⁵

By method, aerosol averages $125, dusting $200 and vacuuming $250. Larger nests cost about $500 and can reach $1,110.⁵

A do-it-yourself kit of wasp spray, dust and a bee suit runs $57 to $227.⁵ Carpentry after a wall job runs about $70 per hour.⁵ Prices are national, so ask for local quotes.

• Keep trash cans covered and clean, and empty them often.²
• Cover food, pet food and drinks, and clear dirty dishes fast. Check a can before you drink.²
• Keep screens in good repair.²
• Pick picnic spots away from trash and dumpsters.²
• Pick up ripe or fallen fruit.¹
• Do not swat. Walk away calmly. If you disturb a nest, protect your face and run.²
• Watch for ground nests in tall grass and mulch beds, and never mow over one.²

Once wasps find food they keep coming back to that spot, so remove the source.¹

Nests start small and quiet in spring, so you rarely notice them. Ohio State says colonies peak from August to late September, with 5,000 or more workers.^2,3

From August to October the wasps shift from protein to sweets, and that is when they ruin cookouts, trash runs and fruit picking.² UC IPM describes the same pattern in California, with scavenging and defensiveness rising through fall.¹

Cold weather ends the colony in Ohio.² In California, mild winters and coastal areas can let some colonies survive.¹ UC IPM says homemade water traps work best as queen traps in late winter to early spring.¹

The German yellowjacket first appeared in Ohio in 1975 and is now the dominant yellowjacket. The eastern and common yellowjackets are native.² German and common yellowjackets nest underground, in hollow trees, in rock crevices and in building crevices. Eastern yellowjackets nest underground.³

Ohio State Extension tells homeowners not to declare war unless a nest is a serious sting hazard, since each nest dies out.³ For nests that are a hazard, it strongly recommends hiring a pro.²

In Ohio, a person who applies pesticides to someone else's property for pay needs a commercial applicator license from the Ohio Department of Agriculture.⁶ Category 10a covers general pest control, and exams need a 70 percent score.⁶ Ask to see the card and the business license.

The western yellowjacket is the most common in California, and it nests mainly in the ground.¹ The German yellowjacket is increasingly common in cities and often nests inside houses.¹ Another yellowjacket, Vespula vulgaris, nests in rotted tree stumps at higher elevations.¹

If the nest is far away, hard to find or underground, UC IPM points to your local Mosquito and Vector Control District, which may remove nests, or a licensed pest control operator.¹

The California Structural Pest Control Board has a Verify a Company or Licensee page. Use it before you hire.⁷ Late summer and fall bring the most calls, as growth slows and wasps look for sugar.¹