The Basel area has been invaded by a new pest—the Japanese beetle—and while officials are trying their best to keep it from spreading, they need the support of the population to help contain the threat.

The Japanese beetle can cause massive damage to many cultivated plants. While the grubs live in the soil and feed mainly on grass roots, the adult beetle eats leaves from various plants. It particularly attacks roses; apple and stone fruit trees; bushes such as hazelnuts, blackberries and raspberries; corn; grapevines; and other types of trees and bushes. The Japanese beetle does not kill the plants directly, but any defoliation can cause them to suffer severe damage.

Unlike in Japan, the Japanese beetle has no natural enemies in Switzerland. Here, it threatens not only the cultivated plants, but also lawns and football fields as well as forest trees. In the worst case scenario—if the Japanese beetle spreads across Switzerland—the federal government estimates the damage to agriculture at several hundred million francs.

The Japanese beetle was brought from Asia to the United States at the beginning of the 20th century, where it caused great damage to plants. In the 1970s, the beetle first appeared in Europe on the Azores. In 2014, it was able to settle in Italy, where it has eaten up entire vineyards. When a population spreads, the number goes into the millions. In Italy and neighboring Ticino, eradication of the Japanese beetle is no longer considered possible—only containment. In contrast, the beetle is believed to still be eradicable north of the Alps, where it first appeared in Kloten near Zürich, in 2023.

In recent months, the Japanese beetle also has been found in the Basel region for the first time. In the area of ​​the Merian Gärten and sports fields in Münchenstein, a total of 38 individuals were found, almost all of them in set-up traps. The areas around the site where the invasive pests were found in traps have therefore been milled and isolated with plastic sheeting. This destroys the beetle pupae and prevents any beetles from crawling out. The affected area includes the training site of ​​the FC Basel first team, which has also been covered; therefore, the team needs to identify a new training facility before they return to training on Monday. As the larvae of the Japanese beetle depend on soil moisture, there is now a general ban on watering lawns and green spaces in the entire infestation area until September 30th, including the lawns of the St. Jakob swimming pool. (However, with the recent frequent rains, that measure is not likely to affect operation of the pool.)

In the hopes of stopping the beetle, the cantonal plant protection services has set traps with an attractant at selected locations in order to immediately detect their presence. All municipal gardening employees have been made aware and monitor Basel’s green spaces for any beetle presence in their daily work. In addition, residents are asked to keep an eye out for the pest. If you find a Japanese beetle, you are asked to catch and report it right away to the Basel-Stadt gardeners at 061-267-6720 or by email at dominik.gugger@bs.ch.   

Identification features: Japanese beetles are only about 1 cm (1/2 inch) long. They resemble the native May and June beetles and the local garden chafers. They have five small white tufts of hair on each side and two larger ones at the rear end of their bodies as special identifying features. Their wings shimmer with a metallic copper color, while their head and body shine greenish. 

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