Thursday, November 18, 2021

WSDA Pest Program trapping season wraps up

Karla Salp

Each year, WSDA’s Pest Program sets thousands of traps throughout the state to catch invasive species that could threaten agriculture. The program surveys for over 130 pests – most of which have not yet been detected in the state.

Japanese beetles

Dozens of Japanese beetles in a ziplock bag
Dozens of Japanese beetles collected from a single trap

It was a record year for Japanese beetle (Popillia japonica) catches - unwelcome news to farmers and homeowners alike. There was one catch in Washington across the river from Portland, a few as usual near Seattle-Tacoma International Airport, but more than 24,000 in the Grandview area. Catching so many in Grandview this year was surprising considering that only three were caught in 2020 between Grandview and Sunnyside combined.

Japanese beetles on rose bud
Japanese beetles devour a 
Grandview resident's roses
The overwhelming number of catches in the Grandview area has many implications. First, WSDA has proposed a 49-square-mile Japanese beetle quarantine to restrict the movement of soil, yard debris, and plant materials that could spread the beetles. Second, WSDA is planning an extensive, multi-year eradication program to try to eradicate the pest – no easy task given the number of beetles already in the area. Finally, WSDA will conduct extensive outreach and trapping in Yakima and Benton counties in 2022. 

Japanese beetles attack over 300 different types of plants including roses, hops, grapes, corn, lawns, and many other crops grown in area gardens and farms.

If there is a silver lining to this beetle infestation, it is that the city, businesses, schools, and people in the vicinity have been open and willing to do what they can to help with WSDA’s response to this invasive pest. Another positive: although nearly 100 traps were placed around area plant nurseries, no beetles were found at the nurseries.

Invasive moths

Male Lymantria dispar
Our trappers set nearly 23,000 traps statewide this year looking for Lymantria dispar – the moth formerly known as the gypsy moth (a new common name has not yet been established.) This moth has devastated forests in the Eastern U.S. where it is established – eating over 300 different types of trees and plants. When there are cycles of large populations, they can strip entire forests from the canopy to the ground, leaving an eerie winter-like scene at the beginning of summer.

This year was a low year for Lymantria dispar catches – only six were found in the entire state. Unfortunately, one of those moths was caught in Eastern Washington just north of Kettle Falls - which is unusual in itself as most moths are normally trapped in Western Washington – and it was also a more concerning variety – Lymantria dispar asiatica, formerly known as the Asian gypsy moth. Lymantria dispar asiatica eats a wider variety of trees (including evergreens) and the females can fly, allowing them to spread more easily.

Apple maggot

apple maggot fly
Apple maggot fly
Our apple maggot (Rhagoletis pomonella) program continued its work of safeguarding Washington’s global reputation for delicious – and pest-free – apples. The program’s work consists of trapping pest-free areas to ensure they remain pest-free as well as trapping around threatened orchards that are near known apple maggot detection sites.

The good news this year is that many of our main apple-growing regions had no catches at all this year: Adams, Asotin, Benton, Douglas, Franklin, Grant, Lincoln, and Stevens counties. Less encouraging was catching 120 apple maggots in Kittitas County and 843 in Okanogan County.

In areas where apple maggots have been detected outside of the apple maggot quarantine area, the county pest boards are responsible for taking aggressive action. WSDA and the Apple Maggot Working Group (an advisory council composed of state and local government, industry representatives, and researchers) began working last year to examine how best to address the growing apple maggot problem in the unquarantined area of Okanogan County. That effort will continue over the coming months.

Asian giant hornet

Asian giant hornet queen trapped by chopsticks against tree with combs capped with white silk from the nest in the tree showing
Asian giant hornet queen from the
third nest with part of her nest
Our Asian giant hornet (Vespa mandarinia) team had a busy season – finding and eradicating three hornet nests in August and September. Every nest was in a tree cavity, each demanding a creative approach to remove the nest. The most challenging nest was about 15 feet up a tree.

Public trapping and reporting again played a major role in locating the nests – two of the three were located after reports from area residents. Despite existing research indicating that the hornets predominately nest in the ground in their native range, all four nests eradicated in Washington over the last two years have been in tree cavities.

Our hornet program will continue for at least three more years. In order for the hornets to be considered eradicated, we must have three consecutive years with no detections. The biggest challenge to success is the lack of a highly-effective trap. While the traps we use catch hornets, they do not appear to be irresistible to them. USDA continues to work on a lure that will be more attractive to the hornets and we wish them much success!

Exotic wood-boring insects

velvet longhorn beetle
Velvet longhorn beetle
Many of the pests we look for are never found. Such is usually the case with our exotic wood-boring insect survey. Imagine trapping for years and never finding what you are looking for. As disappointing as it may be not to find anything, that’s exactly what we hope the results will be as we look for potentially harmful new pests.

This year, WSDA put out over 400 exotic wood-boring insect traps at high-risk sites such as ports, shipping distribution sites, and transfer stations. Trapped areas and other high-risk areas are visually surveyed for signs of wood boring insect activity. One day, they found one.

“This is the first time in all of these years I have trapped a target species,” Don Kitchen, one of the members of the beetle survey team, said.

This past summer, the velvet longhorn beetle (Trichoferus campestris) was detected for the first time in the state in King County near Kent. WSDA responded by setting more traps and conducting visual surveys of the area, although no additional beetles were found. WSDA will continue to put out additional traps, conduct visual surveys of the area, and conduct outreach about the beetle in 2022.

The work continues

WSDA’s Pest Program has had a busy year – and this roundup covers just a handful of the pests they monitor. With their continued work and the help of the public looking for and reporting suspected invasive species, our state should be protected from harmful pests for years to come.