fill rivers with converted plastic bottles

It must have been the end of 2009 and, while no one was looking, a handful of wasps crossed the Nivelle River and sneaked into Dantxaria. We found them a few months later installed in Amaiur, 15 kilometers further down, already in the Batzan region.

Since then, heto vespa velutina has been consolidated throughout the Cantabrian coast, Galicia and the entire Ebro valley. We have been finding and destroying nests throughout the peninsula. And in 2025, nine of them were found in Alcañiz, the first documented case in the province of Teruel.

Given this, the Government of Aragon decided to take action on the matter: set traps made from plastic bottles.

What are they doing? In a joint action by the Forest Guard of the Alcañiz City Council and the Nature Protection Agents of the Government of Aragon traps have been placed on the banks of the Guadalope River to catch the Asian queen wasps as they emerge from torpor.

In fact, there are two types of traps: on the one hand, there are the VespaCatch, which have special holes for these queen wasps. vespa velutina for which, for example, the native wasp does not fit Vespa crabro. On the other hand, handmade traps made with plastic bottles and a pair of black zip ties have also been installed.

The mechanism is the same: they work with a natural attractant made with water, sugar and fresh yeast. Once inside, they cannot leave. In this way, it is hoped that they will be prevented from creating their primary nest and end up forming a new colony.

And does it work? According to Alcañiz, they have already captured 62 Asian wasp queens in what seems like a huge success. The Environmental Biology group at the University of Vigo is not so clear.

This group, coordinated by Sandra V. Rojas-Nossa and Salustiano Mato, has published between 2018 and 2024 a series of works that compare the effectiveness and selectivity of the most used trap models. And the results are bittersweet.

Bittersweet? Yes, it’s true: VespaCatch is the one that records the highest capture rates of the Asian wasp. But it does so at the cost of capturing vulnerable native species. In fact, according to their conclusions, “with the traps tested, bait trapping continues to be environmentally unsustainable and is not recommended as a control method in regions with an already established invasive population.”

To give us an idea, according to Rojas-Nossa data, approximately 100 individuals of other species for each V. velutina captured in spring. It’s true that it’s difficult transfer Galician data to Teruel, but the capture of 62 queens could have caused a small damage to the local fauna of Guadalope.

It is the great paradox of the velutinas: we have reached a point where ending them means ending everything else.

Image | Alcañiz Town Hall via La Comarca

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