Arrival of the Japanese beetle in France: should we be worried?

The Japanese beetle: a pest insect from Asia

Originally from Asia, the Japanese beetle (Popillia japonica) is a member of the Scarabaeidae family. This beetle, also nicknamed Japanese beetle, resembles a horticultural beetle.

One of the peculiarities of the Japanese beetle is directly present on its abdomen. It has indeed small white streaks on both sides of its body. It additionally has five tufts of white silk on each side of the abdomen, as well as two tufts of white silk on the last abdominal segment. The green head and the brownish body have iridescent metallic reflections.

Its abdomen is 8 to 12 mm long and 7 to 5 mm wide. It is possible to differentiate males from females. The latter are indeed provided with flattened shins at the ends, thus making them larger than the males with rounded shins.

The reproduction of Japanese beetles takes place in late spring, in May and June. Females can lay up to sixty eggs.

Why is the Japanese beetle more feared than ever?

This small beetle is greatly feared, because it has the annoying tendency to attack many species of plants. More than 400 types of plants are thought to be affected by the ravages caused by the Japanese beetle. The problem ? Everything goes there: the leaves, the flowers, the fruits… In the garden, the fruit trees are in danger: the cherry tree, the raspberry tree, the apple tree, the peach tree, the plum tree, the apricot tree and the wild mulberry tree. Fruit production, partly weakened by the vagaries of the weather, would therefore again be under pressure.
The threat also hangs over corn, soybeans, beans, asparagus and vines are also at risk. As if that were not enough, it also attacks forest species such as maple or poplar, and the list goes on even longer with ornamental plants, such as roses.

The National Health Security Agency (ANSES) warns of the threat to “hundreds of plant species: the adult feeds preferentially on leaves while the larvae feed on roots”.

To make matters worse, this insect moves quickly, so much so that it could threaten the entire agricultural system depending on the areas invaded. Its rapid expansion within the territory could be accentuated by two factors: it uses human means of transport and performs prospecting flights of up to 3 km to 24 km per year.

japanese beetle
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The Japanese beetle, soon present France?

In Europe, the Japanese beetle was first discovered in the Azores in the 1970s. Since then, it has been spotted in Italy in 2014, as well as in Switzerland in 2017. According to ANSES, the probability that the Japanese beetle entering French soil soon is now very high. The dynamics of human activities simply reinforce a process of expansion already underway.

For ANSES, it is therefore impossible to prevent the entry of this beetle into France. A scientific coordinator at ANSES warns: “It is an insect that moves easily, the temperature and precipitation conditions are favorable to it and since it can consume many species of plants present on French territory, it will have no difficulty in finding sources of food. ”. Like the Japanese beetle, the mole cricket is one of the devouring insects that disrupt agricultural production.

japanese beetle
Credits: Jen Tepp/iStock

Is it possible to avoid the widespread invasion of the Japanese beetle?

As soon as the insect is detected and to prevent too rapid a spread, ANSES recommends intervening at national level by setting up traps. Lures based on the combination of sex and flower pheromones are particularly effective. They should preferably be placed near the points of entry into the territory (ports, airports, roads). It is also important to raise the awareness of professionals in the sectors concerned.

Other solutions should also be considered at different stages of the insect’s development: irrigation during the egg-laying period to drown the eggs or plowing the land in the fall to limit root-loving larvae.