Chewing leaves into lacey skeletons, dessicating acres of grass and fueling the outpour of thousands of gallons of insecticides into waterways, this infamous emerald insect has certainly made a name for itself.

Japanese beetles (Popillia japonica) have been flourishing throughout the eastern United States since they were first introduced to New Jersey in 1916. Theorized to have arrived via Japanese iris roots in the bowels of a cargo ship, the insect has become a persistent invasive species plaguing gardens, farms, natural ecosystems and urban parks throughout the U.S.

Packed into 10-15 mm of metallic green exoskeleton and golden brown wings, they have an innately stubborn knack for survival. Thousands of miles away from their native temperate island habitats, recent studies suggest that warming temperatures throughout North America and consequent extreme precipitation could even improve their feeding and reproduction windows.

But what makes Japanese beetles such odious insects to gardeners, farmers and ecologists alike is their versatility in appetite. Not only do they feed on over 300 herbaceous and woody plants, but they render plants completely destroyed in their wake.

While developing, the larvae can be considered “grass specialists”— they feed on turfgrass roots and stems, severely weakening water and nutrient absorption for low-growing plants and creating large swathes of brown and dried patches in fields and lawns. In the United States, nearly $450 million each year goes towards mitigating the insect’s damage to parks, lawns and golf courses.

Once adults, the beetles continue to tear into leaves, fruit, berries, legumes and flower buds— this includes common field crops like grapes, corn, hops, soy and apples. The insect is specially adapted to reproduce efficiently, allowing females to lay 40-70 eggs and populations to skyrocket in no time.

Dr. Doug Tallamy elaborated on what makes Japanese beetle reproduction so successful. An entomologist and TA Baker Professor of Agriculture at the University of Delaware, Dr. Tallamy gave a talk at Whitman on April 2 describing the role we all can play in promoting insect biodiversity.

“They have what’s called a feeding mating aggregation,” Tallamy said. “A few beetles start to feed on a leaf and they release a sex pheromone which attracts the opposite sex. You can get 100 beetles on a leaf because they’re eating and mating at the same time, which, of course, always defoliates that leaf.”

Defoliation, sometimes called leaf “skeletonization,” occurs when dozens of the beetles congregate on a leaf and, after feeding, leave it riddled with thousands of holes that give it a lacy or skeleton-like appearance. Without their leaves to complete vital processes of photosynthesis, most plants hit by the beetles’ feeding and mating aggregations are quick to die.

Those living on the East Coast and in the Midwest are well-worn to Japanese beetle infestations — but in recent years the beetle has been migrating west, taking the Pacific Northwest by storm.

In 2025 alone, the Washington State Department of Agriculture reports capturing 71,761 in the Yakima and Tri-cities region. This number is nearly three times WSDA’s catch from 2024, and thousands of times larger than the initial, double-digit catches in 2015.

Celia Wood ‘29 describes finding a Japanese beetle in her house back in Portland.

“I found a green and orange beetle on my mom’s flannel while putting in laundry,” Wood said. “Not knowing it was a Japanese beetle and an invasive species, I just put it outside like I would any other bug.”

Wood said she hadn’t seen any insect like it before in her area, but that both her and her mom could attest it matched images of the insect.

In urban regions, interactions like these are becoming increasingly common. Studies have correlated counties with 10% or more developed areas with increased Japanese beetle populations. In major cities like Portland and Seattle, frequent cross-state and international cargo shipments only heighten the opportunity for beetle populations to spread wide and quickly.

But in rural Eastern Washington — the agricultural capital of the Pacific Northwest — a population continuing to grow at this rate could have serious economic and social consequences. Eastern Washington leads the nation in apple and hops production, with sizable acreages for corn and grape growing.

Few farms have reported beetle impacts thus far, but the WSDA is not taking any chances in the Tri-Cities and Yakima region.

Since early April, the agency has been targeting over 7,000 properties in the Tri-Cities region with scheduled insecticide treatments on residential lawns and parks. WSDA crews are not allowed to initiate the free yard treatment efforts until they receive consent from the landowners. As of now, only 26% of the residents have consented, leaving state officials frustrated and worried the outbreak will only worsen.

“Our state’s beetle eradication success or failure hinges on getting access to treat properties,” WSDA’s Pest Program manager, Sven Spichiger, told PNW Ag Network. “Untreated properties become a haven for beetles where they can thrive and multiply. To succeed, everyone in each community threatened by Japanese beetle needs to come together and ensure that all properties are treated.”

Public resistance might hinge on several factors. Crop Life America reports that 67% of Americans support or are neutral towards pesticides. However, under recent food and health campaigns from the federal government, public opinion towards the synthesized compounds in anything from Red-40 to influenza vaccines are worsening. This phenomenon falls under “chemophobia” and can prove a major reason why people distrust pesticide use in agriculture.

There are legitimate concerns surrounding the insecticide’s repeated use. Categorized as “reduced risk” by the EPA and coined as more eco-friendly than chemical alternatives like DDT or pyrethroids, Acelepryn is supposedly the catch-all chemical for the job, but its ecological impact is far from invisible.

Acelepryn’s main active ingredient is chlorantraniliprole, a chemical synthesized from a poisonous South and Central American flower. Chlorantranipole works by binding to insect muscle receptors, inducing contraction and paralysis.

However, chlorantraniliprole is severely toxic to fish, aquatic invertebrates, oysters and shrimp.

It also affects pollinators at an alarming rate. Studies found that even low concentrations of chlorantranipole were enough to kill monarch butterfly eggs.

“Because life-forms have similar physiology, any chemical that harms a plant may harm an animal,” wrote Rusty Burlew, who has dedicated her life to working with pollinators and now serves as director of the Native Bee Conservancy, among other roles. “Now think about this: If a poison designed to kill plants can be dangerous to animals, imagine how dangerous a poison intended to kill one type of animal can be to another. If someone is sloppy about using the recommended dosages, we can get multiple unintended consequences.”

Acelepryn has been prohibited from use in New York. Other reports additionally suggest that, despite claims chlorantraniliprole is non-toxic to humans, it could compromise the connection between the nervous and muscular systems.

Chlorantraniliprole also lingers in environments for months and has high potential for leaching into runoff and groundwater. Insecticide families are already emerging pollutants in the Columbia river. With a half life of up to 1130 days and a location directly next to the Columbia, using Acelepryn throughout Yakima County and Tri-Cities could create serious water quality issues downstream.

The chemical’s directory label additionally suggests target insects could develop toxin resistance over time, forcing a new compound to be made or chlorantranipole to be released in higher concentrations.

“If you look at the history of invasive insects, [insecticide] has never worked,” Tallamy said. “It will work temporarily, but they’ll be back. You’re never killing enough to actually control the population. But you are killing everything else.”

Insecticide treatments are not the only option. Some gardeners recommend applying neem oil to plants, while others suggest kaolin clay. Milky spore disease and Beauveria bassiana, a naturally occurring fungus that kills the beetles, are highly effective at targeting larvae but work on a much slower scale.

Some scientists have considered biological control — blue-winged wasps often flit around gardens and are a prime natural predator for Japanese beetle larvae. Nevertheless, releasing any number of predators into an ecosystem or residential area could have continual ripple effects on local food webs.

Co-planting species of Japanese beetle resistant or even repellant plants is another key solution. Garlic, chives and catnip are regarded as plants the beetle typically steers clear from. Meanwhile, native woody and herbaceous plants such as juniper, spruce and violets are chemically resistant and less palatable to the insects.

However, Tallamy is skeptical of this fix on its own.

“You can load the landscape with trees and bushes and herbaceous plants that they don’t like but if you still have a lot of lawn you’re still going to have [Japanese beetles],” Tallamy said.

“When we plant grass we’re planting exactly what they want,” Tallamy said. “If you really want to control Japanese beetles, reduce the area of lawn because that’s what’s producing the beetles. It only takes a few adults to lay a lot of eggs and if you have a lawn that supports larval development then you’re going to have Japanese beetles.”

This sentiment falls in line with the mission of the organization Dr. Tallamy co-founded: Homegrown National Park (HNP). HNP provides resources for communities throughout the United States to fill their lawns and yards — no matter how small — with native plants to promote clean air and water, biodiversity, flood control, pest control, pollinator health and carbon sequestration.

According to HNP, wide, grassy lawns and non-native, ornamental plants serve little benefit to local ecosystems. Meanwhile, they take up critical space which is already dwindling as urban development continues to expand into ecosystems.

Whitman’s lawns — and the controversial bucketloads of water sprinkled into them — are a prime example of opportunities for native habitat and rich insect and bird biodiversity on campus. Whitman’s Organic Garden, however, might be a step in the right direction.

Ava Frans ’27 is part of the Organic Garden leadership team. The garden, bursting with grasses, crops and flowers, follows organic practices, avoiding insecticides, artificial fertilizers and large open areas. She reports that the team hasn’t experienced a problem with Japanese beetles so far.

Though most of the plants in the garden are staple crops — corn, potatoes, etc. — student gardeners also work to incorporate native species.

“We always have native wildflowers,” Frans said. “I think that [native plants] are something everyone on the leadership team is excited about.”

“We’re just trying to grow as much as we can out here while still respecting and taking care of the soil,” Frans said.

Chemical soil treatments throughout the Tri-Cities are ongoing. There are currently still no public reports of Japanese beetles infesting Eastern Washington’s apple, grape or hops orchards, but the fear of agricultural devastation — worsened by low resident turnout for treatments — leaves WSDA officials tense.

“What we’re really fighting is fear,” Tallamy said. “But it’s typically unjustified. Is what you’re trying to control really worth it when you look up the food web?”