Introduced wasps have become so abundant in many native forests, especially over summer months, that they now pose a major health and safety risk to those working and playing outdoors, as well as impacting on our native biodiversity, experts at a workshop hosted by Victoria University warned.

Dr Darren Ward, an entomologist specialising in wasps and ants at Landcare Research, says that the introduced German and common wasp species can reach densities of over 350 wasps per square metre.

Wasps lead to declines in biodiversity

“They are voracious predators that cause declines in native biodiversity and reduce our ability to enjoy recreation activities,” he said in a statement issued by the university, the Department of Conservation and Landcare Research.

Professor Phil Lester from Victoria’s School of Biological Sciences says summer wasp densities need to be reduced by 80–90% percent of current levels.

“Over the last few years, scientists have been hamstrung by a lack of wasp control technologies appropriate to New Zealand conditions.”

Although he notes that bait stations could be an effective solution.

“We need to attack the wasp problem in the same way that we carry out intensive stoat and rat control in national parks, but unfortunately, the investment in getting these systems on to the market isn’t happening yet,” says Prof Lester.

At the workshop, various experts formed a Wasp Tactical Group to work out a way to tackle our growing problem. This group is now made up a range of stakeholders and scientists. Their aim is to "provide advice for organisations, media and the public, and advocate priorities for science on German wasps and common wasps (Vespula species) in New Zealand."

Biological control needed

Eric Edwards, a senior science adviser at the Department of Conservation, suggests that a large scale approach is needed and “researching options for biological control, such as using pathogens and parasites over the 1 million hectares currently affected, is a wise investment in sustainable wasp control”.

The German wasp (Vespula germanica) arrived in New Zealand in the Waikato with aircraft parts in 1945 and rapidly spread to become a significant pest. The common wasp (Vespula germanica) is thought to have arrived in the late 1970s but at first went unnoticed due to its similar appearance to the German wasp. The common wasp quickly replaced the German wasp in some areas to become the most abundant species, particularly in the South Island.

Activity idea

The German and common wasps are both introduced species. Your students can learn more about introduced species – and whether they are all bad news for native ecosystems – using these articles.
Native and introduced earthworms
White butterflies

Useful links

    Published 3 February 2014