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Weed control without chemicals – how biocontrol is supporting native seedlings in Waingaro

Waikato District Council has been supporting the health of the native ecosystem at Waingaro St Alban’s Reserve using biocontrol measures that support native seedling growth.

“Biological control (biocontrol) is the use of living organisms to depress the population of a pest species. ” says Ben Wolf, Council’s Ecological Planner.

A major pest plant at Waingaro, the weed Tradescantia (Tradescantia fluminensis) creates a dense mat of non-native vegetation across the forest floor, hindering native seedling growth and reducing biodiversity in forested areas.

“In 2015, Council introduced biocontrol beetles into the reserve, followed by fungus in 2018, both specifically targeting Tradescantia fluminensis. As this approach to weed control involves specific targeting, it is widely considered to be much safer than using chemicals.”

Mr. Wolf says biocontrol is, in the long run, a more affordable approach than spraying (agrichemical control), as well as being more environmentally friendly, better for handlers, and offering a longer-term solution for the ecosystem in which it is used.

“After seven years, we are starting to see a major reduction of Tradescantia biomass and a synergistic impact of beetles and fungus working in tandem,” he says.

“As the biomass of the Tradescantia weed is reduced, more light can begin to reach the forest floor and seedlings are able to sprout and become established’’.

‘’Before biocontrol, the Tradescantia mass was too dense to allow most other plants to germinate, but now we are seeing native seedlings coming up where we used to only see Tradescantia. This is a great success for native vegetation at Waingaro, and we expect these measures will continue to support native seedling growth for years to come.”

Landcare Research is spearheading the research and breeding of biocontrol in New Zealand, and further information can be found via their website.