Watch a wasp nest to help detect northern giant hornets

Cassie Cichorz
Pest Program

Paper wasp on a nest in Washington State

Did you know you can help protect Washington from invasive species just by taking a walk around your house or barn once a week? 

Over the last few years, residents of Whatcom County and WSDA staff have noticed hornets attacking paper wasp nests. In 2021, WSDA tracked a hornet and observed it repeatedly visiting the same paper wasp nest. Each visit lasted five to ten minutes and the hornet removed paper wasp larvae.  

WSDA invites you to help watch for northern giant hornets (Vespa mandarinia). Join our community science project to locate active paper wasp nests, watch the nests weekly, and record your observations from June through October. WSDA will continue to invite residents to participate in public scientist trapping too.

Northern giant hornet attacking a 
paper wasp nest on a house in Whatcom County

Paper wasps (Polistes dominula) can grow to about three-quarters of an inch long and have a well-defined “wasp waist” that makes them easy to identify. Paper wasps are typically not aggressive and do not readily attack people, but they can sting if threatened. They form small colonies and build hanging, open-comb nests on building eaves, frames, abandoned cars, or branches of trees and shrubs. Paper wasp nests vary in size and are usually gray to brown in color. They are made up of many exposed cells that are less than an inch deep. Nests typically range from the size of a quarter to a coffee can lid, but can be larger.

Although we invite anyone in Washington to participate in adopting a paper wasp nest, we are particularly interested in observations from Whatcom, Skagit, Island, San Juan, Snohomish, King, Jefferson, and Clallam counties.

Paper wasps tending their nest

LOCATE

Starting in June, locate active paper wasp nests that you have access to and can monitor through October. Log the nest locations using the Watch a Wasp Nest Registration Form. After submission, you’ll receive an email confirmation which will include a unique Nest ID assigned to your nest location. You will need to save this Nest ID to use during weekly check-ins. Access the registration form.

MONITOR

Each week visit the nests. Watch for any hornet or wasp activity happening at the nest. WSDA asks you to monitor the nests for at least five minutes during the day once per week, but you can check the nests as long and often as you would like.

REPORT

After monitoring you will need to report each of your observations on the Watch a Wasp Check-in form. You will also need your Nest ID which was received in a confirmation email. Click here to access the check-in form.

However, if you think you spot a northern giant hornet (it will be significantly larger than the paper wasps), safely take a photo and report it at agr.wa.gov/hornets or by emailing hornets@agr.wa.gov.

Stay Connected

WSDA is dedicated to working with the public and to providing information on northern giant hornets.

• Join the Washington State Hornet Watch Facebook group.
• Join the Pest Program email listserv.
• Follow WSDA on Facebook, Instagram, YouTube, and Twitter. 

With hornet trapping, finding nothing means something

Karla Salp
Communications

Trap contents from a brown-sugar-baited trap in
South Korea, including V. mandarinia and V. crabro

The first of July is a much-anticipated time for Washington’s citizen scientists. It marks the start of the Asian giant hornet (Vespa mandarinia) trapping season. For the past two years, citizen scientists have set hundreds of traps to help look for hornets throughout the state.

Yet very few of those traps have actually caught a hornet. Not catching hornets, however, is good – and provides meaningful information.

WSDA entomologists Sven Spichiger and Chris Looney recently returned from a trip to South Korea where they conducted or began various types of hornet research in partnership with some local collaborators in an area where the hornets are well established.

One of the experiments involved placing five traps - like those WSDA and citizen scientists have been using for the past two years - to look for the hornets. The traps used the brown sugar bait option – an option that was added in 2021 in addition to the orange juice and rice cooking wine bait option.

The mini-experiment suggested that when hornets are around, the traps will catch them. Although the traps were placed several weeks before peak worker hornet season, WSDA was able to trap two Vespa mandarinia and six Vespa crabro (European hornet) specimens from June 9 - 24.

When you run a trap and catch nothing, that is a great result! It suggests that there are no hornets where you live. So, even if you are disappointed that you’ve never caught a hornet, please consider being a citizen scientist again and help us monitor hornet populations in the state. Whether you catch a hornet or not, it provides the data we need to eradicate this invasive hornet.

Not up for trapping hornets? You can also join our Adopt a Wasp program, which only requires five minutes per week watching paper wasp nests on your property. 

Taking hornet nest removal to new heights

Karla Salp
Communications

WSDA's Pest Program uses a buck lift to access
the nest 15 feet up in an alder tree

Last week, WSDA’s Pest Program removed the third Asian giant hornet (Vespa mandarinia) nest of 2021, making it the fourth nest removed since the invasive hornet was first detected in Washington in December 2019. All of the nests have been in the same general area east of Blaine.

Most research on these hornets suggests that they normally nest in the ground and more rarely in trees. But so far, 100 percent of nests found in Washington have been in tree cavities. The entrance to this latest nest was over 15 feet above the ground. A thermal-imaging camera showed the nest itself was below the nest entrance.

The challenge posed by working on a nest so high up was compounded by the fact that the nest was also surrounded by dense trees and vegetation – especially blackberry patches as much as eight feet tall. The team of entomologists and others from the pest program had to use some new tools to eradicate this nest, including a rented bucket lift to raise them over the bulk of the vegetation so they could work safely at the nest entrance.

Just as in the other nest removals, once at the entrance, the team sealed up the tree and vacuumed most of the hornets out before sealing the entrance.

Inspiring Halloween costumes everywhere -
Dan DeVoe prepares to take down the tree with the nest

In addition to the height of the nest, it was also in a decaying alder tree. This made it risky to safely cut the tree down. A trail steward from the Department of Natural Resources was able to help. Wearing a bulky hornet suit, he cut the tree so it dropped right on target. Once the tree was down, he cut it into sections and split the tree open so the team could finish collecting the remaining hornets and the nest.

Queen and the nest

Here is what was found in the latest nest: 

• 10 combs
• 674 total cells
• 86 empty cells
• 128 eggs
• 202 larvae
• 261 capped cells
• 185 workers
• 0 males
• 1 queens
• TOTAL LIFE STAGES – 777

Luckily, none of the three nests eradicated this year have had new queens, meaning the nest was found and removed before the queens could emerge, mate, and left to start new nests next year.

Two of the three nests this year were found from reports made by local residents, and this is the critical time to find nests before creating new queens. If you think you see an Asian giant hornet, take a photo and submit a report at agr.wa.gov/hornets.

WSDA/DNR/USDA team that removed the 
third nest of 2021, fourth nest total

Video of activity at the nest as well as the nest removal is available on WSDA's YouTube channel.