Sam Owens | 10.06.2017

One of the United State’s most notorious invasive species, the Japanese beetle, has been devastating the ecosystems of American cities since it was first discovered in the U.S. during the early 1900s. Many American environments provide the insects with the means to thrive and rapidly expand their populations due to a lack of natural predators, a favorable climate, and an abundance of the over 300 shrubs, crops, trees and other various plants that the beetles feed upon. 

Even though these pests have historically plagued ecosystems of the eastern United States, poorly regulated shipments of infested plants have allowed them to spread to environments throughout America. Over the last 30 years Japanese Beetles have been found in Oregon on a number of occasions, but they have been quickly eradicated thanks to quick and efficient action. However, a new infestation of Japanese beetles has been identified in Northwest Portland, and it is of far greater magnitude than any Oregon has ever dealt with. If it is not managed properly, many plants that are an important part of Portland’s urban landscape could be severely impacted.

It is important to note that a defining part of Portland's culture and general urban aura is the close relationship that the metropolitan area has with the natural world. With remote wilderness easily accessible in every direction, the United State’s largest urban park, and an impressive array of urban forestry and plant life, the city of Portland has been successful in counterbalancing the concrete jungle that characterizes many American cities. This natural element is a point of pride for many residents, and as result the ecosystems and plants that inhabit Portland are a defining part of the city. This is why the recent discovery of more than 12,000 Japanese beetles in the Cedar Hills and Bethany areas is particularly worrisome. These beetles have an appetite for plants like roses, marijuana and blueberries, and the infestation is likely to send a chill down the spines of a few Portlanders.

In order to avoid the consequences of a widespread Japanese beetle infestation, the Oregon Department of Agriculture has devised a Japanese Beetle Eradication Response Plan. However, in order to understand how to successfully rid an area of a growing Japanese beetle population, it is important to first have a better understanding of the beetle itself. The life of a Japanese beetle begins between June and August as a tiny white egg that is laid and buried under the cover of soil; this soil is where the insect will spend the next 10 months and its first three stages of life. After two weeks the insect emerges from its egg as a grub, and over the next few months it uses the roots of turf grasses to nourish and grow. Even at this young age the insect can be harmful, as its appetite for roots limits the plant's ability to absorb water, and patches of dead grass are evidence of grub infested soil. Following a winter buried deep in the earth, the warmth of spring causes the grubs to make their way closer to the surface, where they will feed in preparation for the pupae stage of their life. The insects remain in the solitary confinement of their pupae shell for two to three weeks before emerging as full grown metallic green Japanese beetles.

Although a beetle's adult life only lasts 30 to 45 days, it is during this stage life that they can wreak havoc on plant populations. Japanese beetles are primarily leaf eaters, and they feed on the upper surface of foliage, chewing out the tissue between the veins and giving leaves a skeletal appearance. Although Japanese beetles don’t eat a lot by themselves, the way that they feed as a large population is particularly harmful to plant life. As they eat, they emit a chemical that attracts other beetles to that plant. Due to this the plant becomes overrun and in many cases completely defoliated. The result of defoliation is that  the plant loses its leaves and, most importantly, its ability to photosynthesize. Without photosynthesis, the plant can’t purify air, mitigate water quality, and protect itself from extreme temperature, making it susceptible to disease and potential death.

When Japanese Beetles are fullly grown they are frequently on the move, capable of traveling an impressive 5 miles during their adult life. As a result, diminishing a population during this stage of life is nearly impossible, and a successful eradication plan generally targets eggs and young grubs that reside in the soil. In correspondence with this strategy, earlier this spring, under the supervision of the Oregon Department of Agriculture, a private contractor applied Acelelpryn G, a low risk insecticide, which isn't harmful to humans or house pets and has previously been used in Oregon to successfully eradicate Japanese beetle populations. This application was the first of five years of treatment that the Oregon Department of Agriculture, and Portland as a whole, hopes will effectively rid the area of Japanese beetles.

Although the state’s response has been quick, the effectiveness of this treatment will not be measurable until next summer. For now, all Portland can do is nervously await the insects to reach adulthood, and hope that the city’s cherished plants don’t become another casualty of a Japanese beetle population run rampant.  

Featured image by Ryan Hodnett, published under CC license 2.0.


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