New Zealand EPA consults on moth plant rust fungus

The New Zealand Environmental Protection Authority (EPA) is seeking submissions on an application for release of the moth plant rust fungus Puccinia araujiae. If approved for release, this fungus would be used to help control the weed, moth plant (Araujia hortorum). The submissions period opens on 26 August 2015 and closes on 7 October 2015.

The application, from Northland Regional Council, on behalf of the National Biocontrol Collective (12 regional/unitary authorities and the Department of Conservation) is made under the Hazardous Substances and New Organisms (HSNO) Act 1996.

Moth plant is a tough perennial, broad-leaved herbaceous climber with twining stems, clusters of small cream tubular flowers and choko-like fruit. It can reach over 5 metres when it grows up trees or creeps over the ground, shading out low- growing vegetation. The sap of the fruit and stem is a skin irritant. The weed is considered a threat and cannot be sold, propagated or distributed in New Zealand. Regulation varies from region to region, but most regional councils require landowners or occupiers to remove moth plant from their property.

The plant is native to south-east Brazil, Argentina, Paraguay and Uruguay. It has become naturalised in a number of countries and has been regarded as a weed in most countries it has colonised. In New Zealand, moth plant is widespread from Nelson and Marlborough northwards and abundant north of Tauranga. 

The rust fungus Puccinia araujiae is a highly specific parasite that is expected to severely impact on moth plant, its primary host, if approved for release. Moth plant belongs to the sub-tribe Oxypetalinae. Other members of this sub-tribe, including the exotic ornamental tweedia (Oxypetalum caeruleum), will possibly be affected by the fungus. If necessary, home gardeners could mitigate damage to tweedia by applying an over-the-counter fungicide. There are no native species that belong to the same sub-tribe or tribe as moth plant therefore no native New Zealand plants are expected to be parasitised by the fungus.

If approved, the rust fungus would be the second biological control agent approved for release under the HSNO Act to control moth plant. The first agent, the beetle Colaspis argentinensis, was approved in 2011. The beetle has not yet been released. If the moth plant rust is approved for release, the two agents would be expected to work together to suppress the moth plant.