‘Aggressive’ alligator weed found in Central Hawke’s Bay’s Lake Whatumā

Alligator weed competes with pastures and crops, is toxic to stock and blocks waterways. Photo Supplied

Hawke’s Bay Regional Council has confirmed the presence of alligator weed at Lake Whatumā, near Waipukurau.

Council said the weed is an “invasive pest” and recognised as a severe threat to agriculture and biodiversity.

Listed as an Exclusion Pest under the Hawke’s Bay Regional Pest Management Plan 2018-2038, it is very aggressive, has an exceptionally deep root system and spreads readily from only minimal plant matter.

Iain Maxwell, council’s integrated catchment management group manager, said a biosecurity team identified the weed at the lake on April 12.

“Initial actions focused on notifying properties adjacent to the lake and erecting signage to encourage biosecurity measures to limit further spread.,” he said.

Alligator weed is already a major problem in Northland and infestations have also been identified in Waikato and Manawatu. It out competes pastures and crops, is toxic to stock, blocks waterways and drains and may affect whitebait spawning areas.

Council said it has been in touch with mana whenua, all the lake stakeholders as well as the Department of Conservation, Hawke’s Bay Fish and Game and the Whatumā Catchment group.

“The focus this week is on conducting an extensive delimiting survey to determine how widespread the weed has become. This will include searching the entire Mangatarata Stream as well as any inlets to the lake.”

Maxwell said once the survey has been completed and the full extent of the outbreak is known, this will enable the council to finalise a plan with a goal of eradicating the weed and stopping further spread. On completion, survey results and the management plan will be shared with all stakeholders and the community.