VANCOUVER, Wash. — The Washington State Department of Agriculture will put out more traps in southwest Washington this summer to detect Japanese beetles, a strong-flying and leaf-eating pest found in abundance last summer across the Columbia River in Oregon.
Unlike other Western states, Washington has never had an outbreak of the invasive insect. Last year, WSDA trapped just three Japanese beetles — all at airports in King County.
But the Oregon Department of Agriculture detected a record 369 Japanese beetles in Cedar Mill, a suburb of Portland. ODA has just finished spreading a granular insecticide, Acelepryn, at more than 2,400 residences to kill larvae. ODA obtained a court order to ensure it could get on every property.
Washington has never had to conduct an eradication campaign for Japanese beetles, though it has experience in spraying for gypsy moths, another invasive species that like the Japanese beetle is widespread in the East but has so far been fended off in the West.
“I’m not sure which would be worse, but I know the Japanese beetle would be bad because we’re such an agricultural state,” said Rian Wojahn, WSDA’s eradication coordinator. “It’s a turf pest, and it’s a plant pest. That’s why it’s such a bad pest.”
The USDA has estimated that nationwide Japanese beetles cause $460 million in damage annually.
As grubs, the insect feeds on grass roots. The insects emerge above ground as flying beetles for two months in the summer and attack flowers, fruits and ornamental plants. Japanese beetles are so attracted to roses that traps are baited with the scent of roses.
ODA estimated that a Japanese beetle infestation would cause $43 million worth of damage annually.
Although the judge’s order applied to about 200 properties, ODA spokesman Bruce Pokarney said Thursday that only two landowners could be described as “real holdouts.”
In the end, they attested to their sensitivity to chemicals, and ODA agreed to use an insecticide similar to the organic pesticide that it sprays from the air over residences to eradicate gypsy moths. Pokarney said the alternative insecticide is less effective and more expensive than the chemical used elsewhere.
The operation ended June 7 and went well, he said. “It’s been amazing how this community has recognized the threat of Japanese beetles.”
The insecticide won’t kill the generation of Japanese beetles about to emerge, but is expected to begin thinning the population. Eradication may take four more years, according to ODA.
ODA opted not to spray foliage to kill the insects as beetles. “It would be very intrusive to landowners, and we think we can (eradicate the insects) this way,” Pokarney said.
WSDA plans to set out 325 traps in Clark, Cowlitz, Klickitat, Lewis and Wahkiakum counties, more than triple the usual number for southwest Washington. “Now that they’re close, it could be that some eradication is on the horizon, so we’re definitely staying vigilant,” Wojahn said.