A Council-funded report that investigates wattle infestations around Waitohi/Picton was discussed at last week’s Environment Committee meeting. Led by Lincoln University researchers, the report was commissioned to determine the dominant species of wattles in the area, identify the likely long-term structure of the vegetation and assess its fire hazard now and in the future. The report concludes with management recommendations, cautioning that wattles are notoriously difficult to control and any meaningful control would require substantial funding and a very long commitment.

“The wattle infestations around Waitohi/Picton have been raised by the community as a concern in recent years, especially a perceived link between wattle flowering and allergy symptoms. However, the new report cites several studies from Australia and New Zealand that have found minimal links between wattle pollen and allergies in Australasia,” said Jono Underwood, Council’s Biosecurity Manager.

“In terms of fire hazard, researchers found wattle-dominated stands represent a relatively high fire hazard, with moderate to high flammability material. However, many of the native tree species regenerating under Acacia (wattle) species have low flammability, which suggests that fire hazard risks will decline over time as the landscape transitions to native vegetation.”

“The main species found around Waitohi/Picton, Acacia dealbata, is used for firewood and shelter and can be purchased at plant nurseries. Acacia is not a banned pest species and no regional council in the South Island manages any Acacia species via programmes within their Regional Pest Management Plans.”

“The good news is wattle doesn’t spread like wilding pines, which have wind-blown seeds. Wattles are generally spread through human activity such as land disturbance or soil movement, as their seeds are long-lived in the soil, waiting for that disturbance for their germination,” said Mr Underwood.

“Wattles are widespread throughout New Zealand and are prevalent across other parts of Marlborough. They are usually associated with disturbed areas as they are an aggressive pioneering plant. Due to the widespread nature of wattles and the complexities raised by the recent investigation, managing wattles at the regional scale does not align with the strategic priorities of the Biosecurity function at Council,” said Mr Underwood.

“While broad-scale wattle management is not a strategic regional priority, there are opportunities for communities to decide how to manage wattles locally. There are some great community programmes already in Waikawa Bay and Havelock targeting wattles and other invasive species,” Mr Underwood said.

“The best approach for communities is to look at the wider alignment across ecological restoration initiatives – either existing or new – to find funding and foster the best outcomes for biodiversity. However, for Council, when our resources are limited, there is a need to balance local community desires with our strategic regional biodiversity and biosecurity priorities,” Mr Underwood said.

Lincoln University researchers suggested the most effective way to reduce wattle infestations in places like the hills around Waitohi/Picton is to foster the regeneration of existing native vegetation, reduce pressure from browsing feral animals and aim to close the native canopy.

The full report - Scientific Investigation into Wattle infestations in the vicinity of Waitohi/Picton by Dr Tim Curran, Dr Jon Sullivan and Dr Azharul Alam can be found at: www.marlborough.govt.nz/your-council/meetings

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