Crofton weed – also known as sticky snakeroot or Mexican devil – has been smothering native bush in Australia since the early 1900s. But now a new biological control agent brings hope in managing this invasive weed.
The tenacious and troublesome Crofton weed (Ageratina adenophora), as it is commonly known, has been running rampant in eastern coastal Australia since it ‘escaped’ from gardens across Sydney.
The weed spread rapidly during the 1940s and 1950s creating dense infestations, particularly along waterways and disturbed areas, inhibiting native regeneration and threatening several vulnerable or endangered native species and communities.
Crofton weed is a serious environmental weed that has invaded agricultural lands as well as 150 reserves in NSW. It reduces the ecological value of bush land but also affects grazing land on farms by diminishing their carrying capacity.
This weed has also taken hold on Lord Howe Island, a World Heritage Area, where it is found mainly in non-accessible areas, making manual removal and herbicide control impractical.
A new biological control agent, commonly referred to as Crofton weed rust fungus (Baeodromus eupatorii), that originates from Mexico (where Crofton weed is native) was first introduced to Australia in June 2014. The rust infects the young leaves and stems of the plant, stunting development and disrupting its ability to reproduce.
This agent has proven safe for introduction to Australia through rigorous testing.
The cool and wet conditions that prevail during winter on the eastern Australian coast are perfect for the Crofton weed rust to establish readily after release, and once established in the environment, this biological control agent is self-sustaining, self-disseminating via wind currents, and become a long-term management solution without the need for the rust fungus to be reapplied year after year.
This type of biocontrol option is regarded as the best solution to manage a range of invasive species because it is environmentally benign, cost effective and likely to offer permanent suppression.
Weed biological control using plant pathogens was pioneered in Australia nearly half a century ago with resounding success at preventing a range of weeds from threatening our agriculture, natural ecosystems and biodiversity.
In 2015 and 2016, the research team led a large-scale release program of the fungus in partnership with land managers in eastern NSW, where Crofton weed is a major problem. The fungus was also introduced in national parks in south-east Queensland during autumn 2015 and on Lord Howe Island in July 2016 to help save the picturesque environment from being overrun by Crofton weed.
The Crofton weed biocontrol program has received support from the Rural Industries Research & Development Corporation, Lord Howe Island Board, NSW National Parks and Wildlife Service, Queensland Parks and Wildlife Service, NSW Department of Primary Industries (through the NSW Weeds Action Program) and NSW Environmental Trust.