With dreams of strawberry fields forever, the tiny invasive species known as Popilia japonica first found its way to North America nearly 100 years ago, fittingly landing in the garden state of New Jersey, and they have been slowly expanding their range westward ever since. In May of 2018, the City of Vancouver advised that the insects had arrived, with the Canadian Food Inspection Agency (CFIA) outlining an infested zone around False Creek and restricting the movement of plants and soils in that area.
Native to the northern islands of Honshu and Hokkaido, the fully-grown Japanese beetle measures only one centimetre in length. It features a coppery coloured shell with shades of metallic green, and can be also distinguished by white markings on their sides. Back where they once belonged, these diminutive insects caused little trouble, as numerous natural predators kept their numbers down. Additionally, its preferred food sources were not overly abundant and the temperature in its home latitudes was relatively cool, which together limited the beetles’ reproductive cycle to two-year intervals.
However, having found an appealing habitat in North America, ideal food sources, an inviting climate, and a lack of predators, these beetles were able to increase their reproduction rate to a one-year cycle and have since become endemic in the US east coast.
According to the Canadian Food Inspection Agency (CFIA), the Japanese beetle has a taste for landscape plants, ornamental plants, fruit and vegetable gardens, nurseries, orchards, and agricultural crops. As such, these beetles pose a genuine risk not only to parks and gardens, but to agricultural production as well. Hoping to avoid any potential damage, strict controls have been in place for several decades, with the pest only making limited appearances on the West Coast in that time.
The Japanese beetle, however, finally seems poised to make its breakthrough into BC.
A Day in the Life
A subterranean pest for much of its life cycle, Popillia japonica’s eggs are laid and hatched below the soil where the larva feeds on plant roots in its early stages in life. This introduces an additional layer of difficulty to manage the pest, as it is hard to reach them underground. In the adult stage, it emerges from the soil and starts feeding on the foliage of the plants, and then spreads its wings in search of additional food sources.
The effects of their voracious consumption are leaves chewed through to look like netting and grass fields scattered with clusters of brown. Aside from being an unpleasant sight to the eye, economically it can impact agricultural planning as well.
Free as a Bird
“If nothing was done to control existing sites, then within two years it would cover greater Vancouver,” noted Dr. Murray Isman, Professor of applied biology for the faculty of land and food systems at UBC. “It can fly, so it moves quickly. It’s very prolific, and feeds on a variable range of plant sources, so it can become well established very quickly.”
The important thing now is to get the infestation under control before too much damage is done. The CFIA is going for a chemical approach, using an insecticide called Acelepryn to tackle the problem areas for spot eradication, an approach which has been successful in the past with other infestations such the Gypsy Moth.
“It is the best choice because it has a good use history in Canada for other subterranean species,” advised Dr. Isman. “It is an insecticide that is taken up by the roots and transferred to the area of the plant where the beetles are actually feeding, without having to spray it onto a crop. This reduces the bystander exposure. They need to balance a product that will do the job versus limiting harm to other species. However, it does not harm the plant.”
The topic of chemical insecticides raises the question regarding natural alternatives. For his part, Dr. Isman just wrapped up 35 years of research studying botanical insecticides. He indicated that there are some natural insecticide products based on plant and mineral oils coming through the approval pipeline in Canada, but a balance is required to address the urgency of this situation.
If you’ve got trouble
But how urgent is this beetle outbreak? Does the first sighting of a single Japanese beetle prompt teams of eradicators to spread out across the city? In reality, the response is more measured, with officials monitoring the beetle population using bucket traps, and they have been doing this for a few years. The idea is to look at how many beetles are trapped per week and compare the results over time.
In a quarantine situation, officials expect to find only a few beetles in the traps, but when upgrading to an active monitoring situation, the number of deployed traps and observations increases in order to better assess how quickly the population might be growing. Once 20-40 beetles start to appear in traps regularly, it is considered a problem that needs intervention.
Come and get it
In order to attract the beetles to the traps in the first place, a chemical cocktail composed of the beetles’ favourite things is concocted. A combination of pheromones (either R-Japonilure or a Furanone), and a floral mix of Eugenol, Geraniol, and 2-phenyl Ethyl Propionate (PEP) is mixed Eugenol is derived clove oil, geraniol comes from lemongrass oil, and PEP is a constituent of peanut oil.
Though the Japanese Beetle does not pose any direct risk to human health, the chemicals used to control a potential outbreak are the more likely source of concern. The City of Vancouver approaches pesticide use carefully, but its application may be required in order to minimize the risk of a species that has already caused devastating damage on the east coast of North America.
“There are one of two consequences for Vancouver, if we uphold the cosmetic use of pesticides it means we have to get used to our trees, shrubs and parks getting heavily damaged by this insect. Or conversely we will have to get used to the idea of using insecticides,” said Dr. Isman.
As far as Vancouver officials and BC gardeners are concerned, it is hoped that as June light turns to moonlight, these beetles will be on their way.