Thursday, September 30, 2021

Taking hornet nest removal to new heights

Karla Salp

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

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

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