New option to control moth plant under consideration

3 Sep 2015, 4:42 PM

A new option to control the highly invasive weed moth plant is under consideration by the Environmental Protection Authority (EPA).

Northland Regional Council, on behalf of the National Biocontrol Collective which represents 12 regional councils and unitary authorities plus the Department of Conservation (DOC), has applied for approval to release a rust fungus as a biological control agent for moth plant (Araujia hortorum).

Biological control introduces and establishes natural enemies that prey on or adversely affect the target pest, restricting its ability to grow and spread.

The application is being publicly notified for comment, with submissions to the EPA closing on 7 October 2015.

Moth plant showing pods and flowers.Moth plant in flower.


"Regional and unitary councils and DOC, who have statutory responsibility for managing weeds such as moth plant, believe biological control is the only means of achieving widespread control of moth plant in an environmentally acceptable and cost-effective way," says Joe Carr, who chairs the Northland Regional Council's Environmental Management Committee. "We expect the application to the EPA will be of interest to landcare groups and home gardeners throughout Northland and encourage them to make a submission."

Originally from South America, moth plant is a tough, fast-growing vine that can rapidly climb and smother trees. It grows equally well creeping over the ground, shading out low vegetation such as regenerating seedlings.

Moth plant has become increasingly common along roadsides, forest edges and coastal sites in Northland and is also a problem in urban reserves and gardens.

It has white flowers that turn into large hanging kapok-type pods, each of which splits open to release about 750 seeds with silky threads that are carried by the wind to new sites. The seeds are poisonous to humans, and the pods and stems also contain a milky sap which is a skin irritant.

Existing options to control moth plant including spraying, which can result in unacceptable damage to underlying vegetation, or treatment by hand and collection of seed pods, which is highly labour-intensive.

The application to the EPA addresses the risks, noting that introduced natural enemies must be safe to import. Laboratory testing has found the rust fungus can infect plants in only one closely-related group but that damage to one ornamental plant sometimes grown in New Zealand gardens cannot be ruled out.

Further information on the application and the submission process can be found on the EPA website.