The Asian giant hornet, the world's largest hornet and an invasive species first documented in the state late last year, can attack and kill a honey bee colony in a few hours.
The state Department of Agriculture confirmed the first two sightings of the predator in December, and reported two unconfirmed but probable sightings.
All of the sightings were in Whatcom County. The insect has also been documented in British Columbia.
This spring, scientists are expecting the hornet to emerge again, and are asking for the public’s help in detecting the invader.
In April, the queen hornets come out of hibernation in search of plant sap and fruit to feast on, said Tim Lawrence, director of the Washington State University Island County Extension and a honey bee expert.
The queen then searches for an underground den in which to build her nest and grow her colony over the summer.
Lawrence said the goal is to eradicate the queens before they have a chance to establish a population. If the species becomes established, it could pose a threat to honey bees, which farmers rely on for crop pollination.
The Department of Agriculture will begin trapping queens this spring in Western Washington, with an emphasis on Skagit, Whatcom, Island and San Juan counties.
To report a sighting, residents can contact the department or use the Washington Invasive Species Council’s smartphone app, WA Invasives.
The Asian giant hornet is 1.5 to 2 inches long, and has an orange-yellow head and a striped abdomen, according to the department.
The public can also assist with trapping giant hornets.
The department has developed a guide, which is available on its website, for beekeepers and residents to build their own traps. Traps are plastic bottles filled with a mixture of orange juice and rice cooking wine.
The department asks participants to set traps July through October. Traps can be set in April to trap queens, though catching hornets during this time is less likely, according to the department.
The website notes that participating in trapping increases the risk of being stung by an Asian giant hornet. Those who are allergic to bee or wasp stings should not participate.
Lawrence said while Asian giant hornets don’t generally bother humans, they are known to be aggressive near their nests and honey bee colonies they have taken over.
“The general public should avoid them at all costs,” he said.
Their stingers are longer than those of honey bees, and the sting more toxic, according to the department.
Regular beekeeping suits don’t protect against stings from the Asian giant hornet, and the Department of Agriculture had to order special suits from China, according to a news release from Washington State University.
Farmers need honey bees to pollinate many of their crops. Lawrence said commercial and local beekeepers rent hives to growers of crops such as blueberries, raspberries and brassica seed, which are all grown in Skagit County.
"We can speculate if the (Asian) hornet becomes well-established, (beekeepers) may have to move to different parts of state,” he said. “It's likely the hornets will have more of an impact on the west side of the mountains.”
He said Western Washington is similar to parts of Japan, where the hornet thrives.
The theory is that the Asian giant hornet ended up in North America through international trade, as insects are frequently inadvertently transported on cargo and sometimes deliberately, according to Washington State University.
Lawrence said unlike other honey bee species, the European honey bee has no natural defense against the Asian giant hornet. He said that has been documented by Japanese beekeepers.
“(The hornets) attack and group up on one individual colony and are relentless in their attack,” he said.
It is unknown how the hornets will impact native bee species.
Lawrence said honey bees are already facing threats such as varroa mite infections that can destroy hives and pesticide use.
"(Asian giant hornets) are going to add an additional layer that we certainly don't need," he said.