Invasive wasp threatens North American ecosystems •

A new study led by Dartmouth College has revealed that an invasive wasp – which has already caused significant damage in the Southern Hemisphere – could be spreading across North America. For the moment, it seems that the defenses of nature control this insect.

Experts believe that the Sirex wasp (Noctilio Sirex) has the potential to reproduce at rates two to three times higher in North America than in its native range in Europe, Asia, and North Africa. Although its impact on this new territory has been limited so far, under the right conditions it could spread rapidly and pose a major threat to local ecosystems.

Unlike yellow jacket wasps and other common wasp species, Sirex wasps eat wood instead of fruit and meat. Injecting a fungus and a dose of venom into the trees can weaken them and sometimes even kill them.

Wasps also lay eggs in trees, where their larvae hatch and feed on wood previously digested by fungi. While other invasive species are range limited by their sensitivity to temperature and other climatic factors, wood wasps do not appear to be limited by climate.

Although wasps are considered minor tree-eating scavengers in their native region (Galicia, Spain), in non-native areas such as New Zealand, Australia, Chile, Argentina and d other countries in the southern hemisphere – where they have no natural enemies – they are responsible for major attacks on pine trees and can be very costly to manage. Since entering the United States in 2004 at a cargo port on Lake Ontario, these wasps have spread throughout the northeastern United States and parts of Quebec and Ontario in Canada.

According to scientists, the wasp has the potential to be more than 150% more productive in the United States than in Spain. Its higher reproductive rates in the northeast are partly due to their different relationship to a parasitic worm that sterilizes wasp eggs in Spain, but not in its new territory. Fortunately, due to the relative scarcity of host pines in the northeastern United States and the existence of natural enemies such as parasitic wasps, these regions appear to be more resistant to invaders than initially thought.

“When we first observed the Sirex wood wasp in North America, we thought ‘oh no, we better be prepared for this,'” said study lead author Flora Krivak. -Tetley, Dartmouth invasive species expert “We don’t know how it will go in other parts of the continent but, for now, nature has rallied to its own defense against this wasp.”

However, if the wasp thrives in southern or western states — which have larger pine populations — it could cause significant damage. “This wasp will continue to spread throughout North America and it can be expected that it will eventually appear wherever there are pine trees,” said study lead author Matthew Ayres. , professor of biology at Dartmouth. “The good fortune we have enjoyed so far with the Sirex wasp could change if the insect reaches areas with greater resource availability and fewer natural enemies.”

The study is published in the journal NeoBiota.

By Andrei Ionescu, Personal editor