Nova Scotia’s Unwelcome Guest: The Japanese Beetle
By Mikayla Brown, SMU Service Learning Student
Introduction
As the warm summer months wrap up, so does the dreadful sight of the Japanese beetle (Popillia japonica). These beetles have become increasingly common in gardens, fields, and forests of Nova Scotia (Canadian Food Inspection Agency, 2023). The small beetle may seem harmless to some, but many have come to learn that their presence is not a good sign. The signature mark of the beetle is more commonly recognized before any beetle sightings. This telling mark is seen on the leaves of trees and plants, the beetles eat the foliage leaving a lace-like skeleton behind (Invasive Species Centre, 2024) (Figure 1). The impact of the Japanese beetle is posing a threat to local ecosystems, agriculture, and biodiversity.
Figure 1: Japanese beetles feeding on a peach tree, demonstrating the method and telling sign of their feeding habits (Smith, 2017).
The Journey to Nova Scotia
The Japanese beetle first came to Canada in 1939, hitching a ride on a vehicle aboard a ferry from Maine to Yarmouth, Nova Scotia (Canadian Food Inspection Agency, 2023). Within the same year, three more adult beetles were captured in Yarmouth, and an additional four were found in Lacolle, Quebec (Canadian Food Inspection Agency, 2024). This was the start of the Japanese beetle boom in Canada, which has yet to be eradicated.
While the beetle has been present in Canada for quite a while now, the most recognition in the news began within the past five years. The increase in population size has been rapidly growing these past few years, as seen in NS and PEI (Christine Noronha Talks About a Spike in Invasive Japanese Beetles on P.E.I., 2023), (Hodgins, 2024). A common concern raised is that with warming temperatures and humidity, the population size is projected to increase without mitigation efforts (Kistner-Thomas, 2019). The main concern about this invasive beetle is its impact on agriculture, due to its large consumption of a wide variety of plants.
Life Cycle & Feeding
The two major life stages of the Japanese beetle are the larvae and adult stage; both negatively impacting plant life (Kistner-Thomas, 2019). The female adults lay up to 60 eggs, 8 cm deep in the soil of grassy areas, and the eggs hatch within two weeks. The small larvae eat the grass roots until cold weather, where they spend the winter anywhere from 5 to 31 cm below the surface. In the spring, once the small larvae are fully grown, they pupate, rest for two weeks and emerge as beetles in late June or early July. The typical lifespan is from 30 to 45 days, where they feed on fruit and foliage of over 300 plants. The beetles love summer weather, feeding only on clear summer days with temperatures between 21 and 35 degrees Celsius with relative humidity above 60%. The beetles prefer plants that are in direct sunlight, starting at the top of the plant and working down. Typically, the beetles stay where the food is, but the beetles can fly up to 8km if needed.
These actions cause plants to be more susceptible to illness and death (Althoff & Rice, 2022). A common sight is a cluster of Japanese beetles working away at one plant. This is due to plants releasing pheromones from the beetles eating their foliage and fruit, attracting more beetles.
Figure 2: An adult Japanese Beetle (rfotostock, 2023).
Summary
The eastern hemlock is a vital species for newly developing forests as well as old-growth forests and must be protected from the hemlock woolly adelgid. Eastern hemlocks are important to the diversity and sustainability of a forest as they can stabilize the soils for many types of organisms, as well as help neighbouring species in the harshest of cold weather. HWA can live their lives in the base of the hemlock’s needles, killing them rapidly all over the province. Luckily, the province’s stewardship shines with tree injection strategies which invite the provincial community to be a part of saving the hemlock trees. Make sure to stay up to date with the hemlocks, and we hope to see you out there!
A Growing Problem
As of now, the Japanese beetle does not kill plants fully, unless there is an extreme case. The beetles tend to damage and limit the plant productivity of fruit trees, ornamental shrubs, trees, field crops and turfgrasses (Canadian Food Inspection Agency, 2024). The infestation in the United States is larger than it is in Canada currently, and records have shown that over U.S. $460 million is annually spent on recovery efforts for the damage from the beetles (Kistner-Thomas, 2019). Currently in Canada, the beetle is considered established in Ontario, Quebec, Prince Edward Island, New Brunswick, and Nova Scotia (Canadian Food Inspection Agency, 2024). Due to the predicted rise in temperature and humidity trends from climate change, the beetles are projected to spread farther northward in Canada (Kistner-Thomas, 2019).
Japanese beetle infestations have the potential to cause serious ecological consequences. The beetles have a large consumption of a wide variety of plants, leading to defoliation and weakened plants. In gardens, this results in a loss of visual appeal and reduced food production. For farmers, in severe cases, the impact is even more significant affecting crop yields, which can jeopardize livelihoods and local economies (Althoff & Rice, 2022). Additionally, the feeding habits of Japanese beetles can disrupt local ecosystems. Native insects and birds may depend on one of the 300 plants targeted by these beetles for food and habitat. A decline in these plants can create a ripple effect throughout the food web, affecting pollinators, herbivores, and their predators. The small beetle has the potential to have a very big impact.
What Can We Do?
The earliest way to spot the Japanese beetle is to search for dead patches of grass on lawns. Due to the small larvae feeding on grassroots, it is evident where they are due to dead grass patches. In early Spring, when the small larvae are pupating, it is recommended to spray your lawn with a nematode that attacks the larvae (Christine Noronha Talks About a Spike in Invasive Japanese Beetles on P.E.I., 2023). The Heterorhabditis bacteriophora nematode is most suggested for use (The Fight Against Japanese Beetles, 2020).
The second approach is to kill the adults by collecting and submerging them in soapy water (Hodgins, 2024). It is important to not squish the beetles because they release a pheromone that attracts more beetles. In addition, there are adult capturing traps that can be used, but they attract beetles using a pheromone (Althoff & Rice, 2022). These traps tend to attract more beetles than they capture, leaving nearby plants susceptible to more damage (Althoff & Rice, 2022).
Additionally, the government has implemented mitigation efforts. D-96-15 refers to a set of phytosanitary requirements to help prevent the spread of Japanese beetle in Canada and the United States (Canadian Food Inspection Agency, 2024). This directive regulates the movement of plants and soil within North America, to reduce the chance of human-assisted spread to new areas. For more information on D-96-15, explore this link.
Conclusion
In conclusion, this little beetle has a larger impact than one might assume. The pesky beetle travels in groups leaving plants bare and skeletonized, feeding on 300 different plants, leaving many concerns. It is important to continue mitigation efforts to stop the spread of these beetles globally.
For more information on invasive species in Nova Scotia check out the Nova Scotia Invasive Species Council website!
References
Althoff, E. R., & Rice, K. B. (2022). Japanese Beetle (Coleoptera: Scarabaeidae) Invasion of North America: History, Ecology, and Management. Journal of Integrated Pest Management, 13(1), 1-. https://doi.org/10.1093/jipm/pmab043
Canadian Food Inspection Agency. (2024, August 19). D-96-15: Phytosanitary requirements to prevent the spread of Japanese beetle (Popillia japonica) in Canada and the United States. inspection.canada.ca. https://inspection.canada.ca/en/plant-health/invasive-species/directives/horticulture/96-15
Canadian Food Inspection Agency. (2023, June 28). Popillia japonica (Japanese beetle) - Fact sheet. inspection.canada.ca. https://inspection.canada.ca/en/plant-health/invasive-species/insects/japanese-beetle/fact-sheet
Christine Noronha talks about a spike in invasive Japanese beetles on P.E.I. (2023, August 23). [Video]. CBC. https://www.cbc.ca/player/play/video/1.6944207
Clausen, C. P. (1927). The parasites of Popillia japonica in Japan and Chosen (Korea), and their introduction into the United States / by Curtis P. Clausen and J.L. King and Cho Teranishi : v.1429(1927) (Vol. 1429). U.S. Dept. of Agriculture, 1927.
Hodgins, M. (2024, August 2). Japanese Beetles eating away at plants in Halifax again this summer. CityNews Halifax. https://halifax.citynews.ca/2024/08/02/japanese-beetles-eating-away-at-plants-in-halifax-again-this-summer/
Kistner-Thomas, E. J. (2019). The Potential Global Distribution and Voltinism of the Japanese Beetle (Coleoptera: Scarabaeidae) Under Current and Future Climates. Journal of Insect Science (Tucson, Ariz.), 19(2). https://doi.org/10.1093/jisesa/iez023
Invasive Species Centre. (2024, September 11). Japanese Beetle – Invasive Species Centre. https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/invasive-insects/japanese-beetle/
Rfotostock. (2023, July 21). Japanese beetle. [Photograph]. Pixabay. https://pixabay.com/photos/japanese-beetle-beetle-insect-8137606/
Smith, Z. (2017, June 28). Japanese beetle feeding on peach tree [Photograph]. Wikipedia. https://en.wikipedia.org/wiki/File:Japanese_Beetle_Feeding_on_Peach_Tree.jpg. Creative Commons Attribution-Share Alike 4.0 International License.
The fight against Japanese beetles. (2020, April 30). https://simcoecountymg.ca/the-fight-against-japanese-beetles/#:~:text=The%20suggested%20nematode%20for%20Japanese,insects%20that%20start%20as%20grubs.