Stinkbug invasion in Turkey threatens world hazelnut supplies

The world’s hazelnut supplies could be threatened by a stinkbug that has recently invaded Turkey, scientists have warned.

The brown marmorated stinkbug, which is native to north-east Asia, has been spreading across the world in shipping containers, breeding freely thanks to warmer temperatures and a lack of natural predators.

The stinkbug– named for the pungent chemicals it produces as a form of defence – was seen in Turkey for the first time in 2017, after wreaking havoc in neighbouring Georgia. Since then, the insect has spread through at least eight Turkish cities, mostly across the Black Sea region, where about 70% of the world’s hazelnut supply originates.

If the stinkbug’s spread cannot be contained, about 30% of hazelnuts could be damaged, warned Prof Celal Tuncer from Ondokuz Mayıs University’s plant protection department. This corresponds to about a fifth of the world’s supply.

This dependence on Turkish hazelnuts has prompted the industry as well as scientists to call for rapid action against the stinkbug.

At a conference in January, discussions focused on fighting the invasion through the dissemination of a natural enemy: Trissolcus japonicus, commonly known as the samurai wasp. The method of using pests’ natural enemies is known as biological control, and is considered an eco-friendly alternative to the use of insecticides.

Samurai wasps, tiny creatures of two millimetres, lay their larvae inside the stinkbugs’ eggs, which are then destroyed.

One potential problem with this approach is that it usually requires more time than Turkey’s hazelnuts appear to have. Regulations require extensive research before releasing a biocontrol agent in order to ensure that it is not harmful to the local ecosystem.

In the US, for instance, the bureaucratic procedures of releasing the samurai wasp took so long that eventually the species found its way there naturally.

Tuncer said Turkey should seek ways to expedite the process by relying on existing research elsewhere, as a considerable amount of preliminary research has already been completed in Europe.

İlyas Edip Sevinç, the head of the Black Sea Region Hazelnut and Hazelnut Products Exporters’ Association, said taking time to thoroughly analyse the risks of samurai wasps would be ill-advised as the stinkbug was already established and posed such a threat.

So far, farmers have been relying on insecticides against the stinkbug, but this may prove more difficult as the population increases and spreads across the region.

Temperatures in the coming months will play a crucial role in the health of this year’s hazelnut crop. In 2019, chilly weather delayed the stinkbugs’ emergence from hibernation, allowing the nuts enough time to grow their protective outer shells. This year, meteorologists have warned of above-average temperatures, meaning the nuts may not be as fortunate.