The Japanese beetle has already been present in Italy and Switzerland for several years. The probability that it will enter France is high. This pest represents a threat for hundreds of plant species. In order to have a chance to eradicate it, it will be necessary to intervene as soon as the insect is detected.
The Japanese beetle (Popillia japonica) has settled outside of its native Japan, first spreading to the United States before reaching Europe. It was spotted for the first time in Italy in 2014 and in Switzerland in 2017. ANSES, the French National Health Security Agency, has assessed the probability and impact of this insect entering France, and it has recommended measures for monitoring and fighting the insect. “For the moment, it has not been detected in France, but there is no reason why it should not enter the country,” explains Christine Tayeh, scientific coordinator of the Expertise on Biological Risks unit at the Plant Health Laboratory of ANSES. “The expertise has shown that nothing can be done to prevent it from entering France. It is an insect that travels easily, and the temperature and precipitation conditions are favorable. The Japanese beetle also consumes many of the plant species found in France, so it will be easy for it to find food.”
Possible damage to hundreds of plant species
The arrival of the Japanese beetle is a cause for concern. An adult prefers to feed on leaves, while the larvae feed on the roots of host plants. More than 400 species of plants are concerned, a hundred of which are present in metropolitan France. These include plants grown for food purposes: plum, apple, vine, corn, sota, beans, asparagus, forest species like the flat maple or poplar, ornamental plants like roses, as well as some species found on lawns and turfs. By consuming the leaves, the Japanese beetle reduces the leaf area, which reduces the plants’ photosynthetic capacity, thus potentially their yield.
The challenge of monitoring: detecting the beetle as soon as it enters the country
It is impossible to prevent the beetle from entering France: it can fly in its adult stage (from late May to September) and it can also have a hitchhiking behavior, which means that it can be transported on any surface, not just the plants it feeds on. The strategy consists in detecting its presence early, by using traps equipped with mixed lures (combination of sexual pheromones and floral attractants). These traps should be placed in strategic locations, at the borders with the countries where the insect is already present and near key points of entry such as ports or airports and transportation networks. The professionals of the different sectors concerned should also be well informed.
Preventing its settlement with appropriate pest management measures
It is essential to act as soon as the insect enters the territory. “We believe that there is a chance to eradicate the Japanese beetle at the very beginning of the invasion, if we deploy dynamic surveillance and pest management measures while the population is still small and isolated. The operations to eradicate the Japanese beetles in Oregon and California were successful in this context,” explains Christine Tayeh.
If an insect is detected, the ANSES group in charge of the expertise recommends delimiting an infested area, which will be subject to reinforced surveillance. A combination of several control methods should be used, according to availability and authorizations for use. This includes mass trapping, the use of synthetic phytopharmaceutical products and biological control. Additionally, some cultural practices have proven to be efficient in reducing the damage caused by adult Japanese beetles and their larvae. These include reducing irrigation when eggs are being laid and tilling the soil in the fall. If such actions are not deployed immediately after detecting the insect, preventing its spread after it has already settled in France may take a very long time and the chances of succeeding are very low, according to the experts.
For more information:
anses.fr
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