Privet under pressure

Friday 9 October 2015

Bay of Plenty Regional Council released a new privet-eating insect at a trial site in Bethlehem, Tauranga this week, in an effort to improve control of the unpopular pest plant.

Bay of Plenty Regional Council Senior Biosecurity Officer, Shane Grayling is excited about the release of privet lace bug (Leptoypha hospita) but said it will be a few years before they’ll know how effective the insect will be for controlling privet.

“A lot of people blame privet for their allergic reactions, so it’s great to have a potential new control option. Both the nymphs and adult privet lace bugs feed by piercing and sucking on privet leaves, causing dieback in the branch tips.

Weather conditions, predator insects and a range of other variables can affect how well a new biological control agent establishes, reproduces and feeds. It’s only by trialling it in the field that we’ll see what situations it can perform best in. We won’t be distributing the privet lace bug more widely until we’ve seen how well it works and built up enough stock at the trial sites,” Mr Grayling said.

Landcare Research has developed the bug as a biological control agent for Chinese privet (Ligustrum sinense). Developers hope it will also have some spill over effect into tree privet (Ligustrum lucidum).

Regional Council has supported the development along with other councils under the National Biocontrol Collective. The bug originates from China and Malaysia. Thorough testing and assessments have been completed to make sure the bug won’t threaten native wildlife or agriculture in New Zealand. Other biological control agents are already being used in New Zealand to help control weeds like St John’s wort, ragwort and buddleia.

Mr Grayling warns that improved privet control may not be a magic cure for all allergy sufferers. Recent studies by the Auckland Allergy Clinic have found that pollen from grasses, plantain, and birch can be greater contributors to allergy problems.

“Another study that explored offensive or irritating scents found that there was little difference between privet and other scents, including jasmine, lavender and honeysuckle, and many people couldn’t tell the difference.

Privet is a weed that we encourage people to control. We can provide advice on effective control methods, but recommend that allergy sufferers seek medical advice and consider what else is growing nearby too,” Mr Grayling said.

ENDS

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