(lat. Popillia japonica)
The Japanese beetle is an invasive, polyphagous pest that is becoming increasingly widespread in agriculture, horticulture and on lawns. It travelled over from Japan to the USA at the start of the twentieth century and is now a key pest on green areas as well as on sports and golf courses in eastern USA.
It was discovered for the first time in Europe in Italy in 2014 and has since continued to spread and cause considerable damage. It travels over as eggs or larvae in the root balls of retail plants.
In the EU and Switzerland, it is classified as a quarantine pest, meaning that it must be reported and combated.
The Japanese beetle is a species of scarab beetle (lat. Scarabaeidae).
It is approximately 8–12 mm in size and resembles our domestic garden chafer in appearance.
Important characteristic: Five white tufts of hair on each side of its body, including two clearly visible tufts at the rear.
Its larvae are typical grubs.
Lifecycle of the Japanese beetle
Egg-laying from May/June up to 10 cm beneath the surface.
The larvae hatch after around two weeks and feed on plant roots.
In late autumn, the larvae retreat to hibernate through winter in deeper layers of earth.
In spring, the larvae return to the upper layers and begin eating the roots again.
Pupation after four to six weeks.
The beetles hatch in May/June; main flying time is mid-May to mid-August.
The adult beetles live for around 30–45 days.
The development from egg to adult beetle usually takes around a year.
Damage caused by the Japanese beetle
Both the beetle and its larvae (grubs) are capable of causing significant damage in large numbers.
The beetle feeds on flowers, leaves (skeletonising) and fruit to the point of total defoliation.
The grubs feed on plant roots in the ground, which can result in the death of the plant.
Which plants are affected by Japanese Beetles?
The diet of the Japanese beetle is diverse and includes over 300 types of woody plants of various classes, including acorn, beech and oak.
The same applies to green areas, vegetables, ornamental plants, fruit trees, grapevines and agricultural crops such as maize, potatoes, asparagus and tomatoes.
Combating the Japanese beetle with beneficial nematodes (roundworm)
Nematodes are tiny, threadlike soil organisms approximately 0.6 mm long. They are a natural enemy of the Japanese beetle. The nematode species Heterorhabditis bacteriophora specialises in Japanese beetle larvae (among other insects) and can use it for its own nutrition and reproduction.
Which stages of the Japanese beetle are susceptible to nematodes?
The second and third larvae stages of the Japanese beetle can be successfully combated with the nematode Heterorhabditis bacteriophora.
Effective against Japanese beetle larvae
nema-green® contains nematodes of the Heterorhabditis bacteriophora species for biologically combating the larvae of the Japanese Beetle.
The effectiveness of the Heterorhabditis bacteriophora has been demonstrated by various scientists in a wide range of field tests:
Our beneficial nematodes have been in use in the Italian regions of Piedmont and Lombardy since 2017, where they combat Japanese beetle larvae on pastures and meadows.