Partnering with the NSW community for large-scale releases of a new agent

By Louise Morin, CSIRO Biosecurity Flagship

A new biological control agent for crofton weed, the rust fungus Baeodromus eupatorii, is now available for widespread release in NSW.

The CSIRO Biosecurity Flagship, with support from the NSW Weeds Action Program administered by the Department of Primary Industries, is undertaking a release program in partnership with the community in 2015 to facilitate releases of the fungus at several strategic locations across the range of crofton weed in NSW.

Crofton weed (Ageratina adenophora) produces copious quantities of windborne seeds, spreads rapidly and once established at a site reduces its agricultural or ecological value.

Crofton weed is declared as a class 4 noxious weed in several local government areas along the NSW coast. This means that its growth must be managed in a manner that continuously inhibits its ability to spread. While crofton weed can be managed by manual removal and herbicide applications, the extent of current infestations and their inaccessibility in some instances make control with traditional methods uneconomical and impractical. Biological control is the only sustainable method to control crofton weed at the landscape scale and reduce spread and infestation of new sites in NSW.

Biological control relies on highly specific natural enemies introduced from native range of the target weed to help achieve sustainable control. In the 1950s, two biological control agents were introduced for crofton weed in Australia: the fly — Procecidochares utilis, that causes galls on stems, and the leaf spot fungus — Passalora ageratinae, that causes necrotic lesions on old leaves.

While these agents cause some damage on plants, their impacts on populations of the weed have been negligible. The crofton weed rust fungus, which originates from Mexico, has recently been investigated to enhance biological control of this widespread, coastal weed in eastern Australia. It infects young leaves and stems of crofton weed and has great potential to reduce competitiveness, reproduction and spread of the weed.

The rust fungus was thoroughly tested to demonstrate that it would not pose a threat to economic and native plant species before it was approved for release in Australia in May 2014. During winter 2014, the fungus was released at five sites within national parks and conservation areas on the NSW South Coast and north of Sydney.

These initial experimental releases demonstrated that the fungus can establish readily in the field providing that the material used for release lasts for several days and that conditions are conducive for infection at some stage during that period.

Close up of crofton weed rust fungus pustules on the underside of the leaf photo by K. Turner

If you are interested in participating in the release program, please contact us. Rust-infected material suitable to make releases will be provided at no cost to community members either via the post or at field days (locations and dates TBA). Participants will be provided with simple guidelines on how to make the release and to monitor establishment and spread of the agent. In return, they will be expected to provide details on their release site and feedback on their monitoring activities.

For more information contact:

CSIRO Biosecurity Flagship, Canberra

Dr Louise Morin, Tel: (02) 6246 4355, louise.morin@csiro.au

Mr John Lester, Tel: (02) 6246 4325, john.lester@csiro.au