Looking for evidence-based control protocols
Category: National. Posted: 19 June 2026
Rory Johnson receives an NZBI Scholarship
Horizons Regional Council Pest Plant Biosecurity officer Rory Johnson has been awarded an NZBI Scholarship to help him study control methods for the invasive aquatic plant Senegal tea.
In his application, Rory says:
My proposed research investigates effective control methods for Senegal tea (Gymnocoronis spilanthoides), Although currently limited to small populations in the North Island, it is classified as an unwanted organism under the Biosecurity Act 1993 due to its potential to spread widely.
Despite its recognised threat, existing control approaches across New Zealand remain inconsistent, with regional councils reporting variable outcomes from herbicide control efforts. My study addresses this critical gap by conducting a replicated, field-based trial comparing the short-term effectiveness of herbicide treatments (glyphosate, metsulfuron-methyl, and a glyphosate/metsulfuron mix) in the Waikato River delta.
The results will provide regional councils with evidence-based recommendations to standardise control protocols, reduce management costs, and improve response efficiency.