Events Icon


View Events
Events Icon

Smart Partner Program

Learn More
Subscriber Login

Bug of the Month July 2019


Japanese Beetle

By Jean-Philippe Parent, PhD
Research Scientist, Agriculture and Agri-Food Canada
Saint-Jean-sur-Richelieu Research and Development Centre

Simon Chaussé
MSc candidate, Agriculture and Agri-Food Canada / Université de Montréal
Saint-Jean-sur-Richelieu Research and Development Centre

Julia Mlynarek, PhD
Research Scientist, Agriculture and Agri-Food Canada
Harrow Research and Development Centre

Japanese beetle Source: Simon Chaussé

The Japanese beetle is an invasive pest that affects both growers and homeowners. This pest has been present for many years in Eastern Canada, with its first detection having occurred in 1936 (NS and QC). In 2017, the Japanese beetle appeared for the first time in BC sparking considerable efforts toward its eradication. So far, the Prairies don’t have this pest, but Agriculture and Agri-Food Canada actively monitor for its presence through a Canada-wide Japanese Beetle network.

This bulky scarab is 10 mm long by 6 mm wide with a metallic green head and thorax and copper-coloured wing covers on its back. This beetle has one generation a year emerging usually in late June / early July and present for 6 to 8 weeks. During this time, it can defoliate more than 250 varieties of plants ranging from berries (strawberries, blueberries, raspberries), grapes, tree fruits (peaches, apples), roses and soybean.

Skeletonization of leaves by Japanese beetle feeding Source: Simon Chaussé
Skeletonization of leaves by Japanese beetle feeding Source: Simon Chaussé

While they are generalists, Japanese beetles are quite picky eaters: they only eat the soft parts and avoid the veins of the leaves, leading to a characteristic skeleton pattern. The eggs laid during the summer will hatch in about two weeks and the larvae will grow, causing major feeding damage on surrounding roots, grass being one of their favourite foods.

Japanese beetle larvae Source: This photo links to a fact sheet by Canadian Food Inspection Agency

They hibernate in the soil over winter and begin feeding in spring, pupate and emerge as adults.

Canadian observers detected a parasitoid of the Japanese beetle in 2013. The tachinid fly Istocheta aldrichi, lays easily visible eggs on the thorax of the Japanese beetle The egg then hatches and the larva of the fly kills the host by devouring it from within. Its presence is well known in the province of Québec and Eastern Ontario, but is not known in western Canada. The impact of this parasitoid on pest populations in Canada is still not well known, but research efforts by Agriculture and Agri-Food Canada and the Insectarium of Montreal aim to find answers.

Parasitized Japanese beetle Source: Jean-Philippe Parent

Japanese beetle traps have been efficient at catching both males and females in large numbers through a mix of sex pheromones and floral bait. While these traps are efficient,  multiple anecdotal reports suggest an increase in the abundance of the Japanese beetle in the surrounding of the trap, increasing pest damage. Agriculture and Agri-Food Canada in collaboration with Université de Montréal are experimenting to verify this claim and properly advise both growers and homeowners on the best strategies to adopt when trapping the Japanese beetle.

Model of a Japanese beetle trap (in green and yellow) Source: JP Parent