As the noxious tree privet is beginning to flower, an investigation has revealed the link between the plant and health impacts is weak.
Fewer than 3 per cent of people tested with perceived privet-related health complaints actually showed privet pollen in their blood tests, a meeting of the Environment and Services Committee heard in December.
These results were found in an investigation by staff into options of linking the control of privet directly to privet health-related issues through allergy tests.
The plant, which flowers from January to March can cause severe allergic reactions for those who suffer from respiratory problems. Among other ailments it can also cause vomiting, diarrhoea, gastroenteritis, and dermatitis.
The broad leafed hairless shrub can grow to 10m in height, and produces clusters of white flowers and black or blue black berries from January to March.
At the meeting the council's urban privet programme was reported to be delivering a much higher level of productivity through the use of a contractor.
The cost of the removal of privets had reduced from $526 to $260, and rapid progress on reducing privet in the urban environment was being made.
The council class the plant as a "total control plant pest" with the long-term goal of eradicating it. The most effective form of removal of large plants is to be stump cut and treated with herbicide. Smaller plants could be dug out and burnt, composted, or taken to a commercial tip. The landowner was responsible for the control of these plants on their property, but in some cases the council will control the plant, or help the landowner to do so.
A council spokesperson said it was important for people who thought they had a tree privet to be certain before calling the council, because there were a lot of similar plants around.
The Chinese privet flowers later in the year, and produces similar flowers and berries. It is a smaller shrub but can cause the same health impacts.