Invasive weed pest found in Hawke’s Bay

Hawke’s Bay Regional Council has identified the Senegal tea weed pest in the Clive River and the Karamu Stream, the first time the pest has been found in the region. 

Listed as an “exclusion pest” under the Hawke’s Bay regional pest management plan 2018-2023, Senegal tea is an aquatic and aggressive pest native to South America. 

Regional council catchment management biosecurity lead Matt Short said the next few weeks would be crucial to determine the spread. 

“Senegal tea becomes dormant over winter and dies back to its roots, then re-sprouts in spring. With the plant already dying back in places, it’s important we use this small window to identify the scale of the spread. 

“The plant was initially detected using environmental DNA (eDNA) in water samples taken from Te Awa Mokotūāraro (Clive River). 

“We will now be surveying all streams and inlets that lead to the two waterways to find the locations and are encouraging the community to play their part in protecting our awa,” Short said. 

“We’re asking everyone using these waterways — whether you’re on a boat, a jet ski or walking on the berms — please check your gear and equipment for any weed fragments and leave them at the site, clean your gear thoroughly, then leave it out to dry before using again.” 

Senegal tea forms rounded bushes up to 1.5m tall. Usually rooted on the edge of waterways, the pest plant spreads quickly and forms infestations over deep water, blocking drains and causing flooding. 

“Senegal tea also out-competes all other species in shallow freshwater habitats and prevents native species establishing, while blocking light and food sources for other species.” 

Once surveying was completed and the full extent of the infestation known, the council would finalise a control and management plan — with the goal of slowing the spread and eradicating the weed.