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Wasps Plague Riverbanks says HBRC

Wasps Plague Riverbanks

There is a population explosion of wasps along Hawke’s Bay riverbanks and Hawke’s Bay Regional Council is warning people to take care along river berm areas.

“If there’s a large amount of wasps around, our advice is to leave the area, and certainly avoid going into the undergrowth where you may disturb a wasp nest,” says Vince Byrne, HBRC’s rivers manager.
It is not known why wasps have increased to such large numbers in these areas but there have been reports of similar problems in other parts of the country. 

http://www.hbrc.govt.nz/our-council/news/latest-news/media-releases/article/49