Information package to support application to release the rust fungus Baeodromus eupatorii for the biological control of crofton weed (Ageratina adenophora) in Australia

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Morin, Louise ORCID ID icon




Prior to 1984, when the Biological Control Act was enacted, crofton weed (Ageratina adenophora; Asteraceae) was a target for biological control in Australia. Surveys of natural enemies of crofton weed in Mexico, the region of origin of this weed, undertaken by South African colleagues in 2008, identified the rust fungus Baeodromus eupatorii as a potential biological control candidate agent. The rust was imported (permit no IP11016131) into the QC3 Microbiological area of the CSIRO Black Mountain Containment Facility in Canberra (QAP A1280) in December 2011. Once a culture of the fungus was established, a series of tests were performed to investigate its host-range. The selection of the 60 non-target plant species for testing was based on a recent molecular phylogeny of tribes in the family Asteraceae. Each species was tested in two separate trials (unless otherwise indicated; up to five replicates per species per trial) and crofton weed plants were used as positive control. Results demonstrated that B. eupatorii is a highly host specific rust fungus, being capable of successfully developing only on three species within the Ageratina genus (A. adenophora–crofton weed, A. altissima, A. riparia). Across all experiments, both crofton weed and A. altissima consistently supported development of abundant pycnia and telia, which produced basidiospores that were capable on infecting either species, demonstrating that the rust can complete its life cycle on these hosts. In contrast, A. riparia was not as suitable a host for B. eupatorii as these other two species. While the rust produced abundant pycnia on a few very young, still expanding leaves of A. riparia when a very high density of inoculum was used, in the standard host-specificity trials pycnia were infrequently produced and telia were often associated with necrosis. All other 58 non-target plant species tested, which included a large number of other representatives from the Eupatorieae tribe (including the two Australian native Adenostemma species) and representatives from across tribes related to Eupatorieae within the sub-family Asteroideae of the Asteracea family that are present in Australia, were either rated as immune or highly resistant to the rust. The possible infection of A. riparia in the field, should B. eupatorii be released in Australia, would not pose a problem since this species is an undesirable environmental weed. Damage on A. altissima (syn Eupatorium rugosum) is most likely to occur in the field, but as far as we know this species is not widely grown in gardens in Australia and it has been assessed by DAFF Biosecurity as posing a high risk of becoming a weed in Australia. We conclude that the level of risk associated with releasing B. eupatorii is acceptable and that it will be a potentially effective biological control agent. We seek permission for its release in Australia.



Plant Pathology

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Morin, Louise. Information package to support application to release the rust fungus Baeodromus eupatorii for the biological control of crofton weed (Ageratina adenophora) in Australia. Canberra: CSIRO; 2013.

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