Prioritising targets for biological control of weeds - a decision support tool for policy makers

This report outlines a framework of the overall process of prioritising targets for biological control and includes a decision support tool that enables policy makers to determine whether biological control is a suitable option for a proposed target species.Introduction Establishing effective biological control agents in Australia is costly in both resources and time, yet it is often a valuable component of weed control. It has been estimated that biological control of weeds in Australia has provided around $10 billion worth of agricultural protection over the past century. To date significant investment has been made in the selection process of biocontrol agents and the identification of priority weeds for biocontrol. However there is no nationally agreed system that facilitates prioritisation of weed targets for biological control. The Department of Agriculture commissioned ABARES to develop:• a framework that outlines the overall process of prioritising targets for biological control and• a decision support tool that enables policy makers to determine whether biological control is a suitable option for the proposed target species.A recent work related to the selection and prioritisation of weeds for biological control targets was published by Paynter et al 2009 (hereafter \u27Paynter\u27). Paynter was used as a basis for discussion about how to assist policy makers in assessing whether biocontrol is an appropriate option for weed control.The proposal for a decision support tool for policy makers was discussed at a workshop fully recognising that such a system would need to have a science basis that is both transparent and repeatable to be rigorous. The participants were experts in biocontrol or other weed science, state representatives and other relevant stakeholders. The proposal was outlined in a background/discussion paper and provided to participants prior to the workshop. The purpose of the paper was to provide participants with relevant background information and a proposed approach for a decision support tool for policy makers to be debated and progressed at the workshop.Aim of the workshop and background/discussion paper The workshop was held in Canberra on 4 April 2013. The objectives of the workshop were to:• discuss whether the approach based on Paynter is suitable as a decision support tool at the policy level to prioritise targets for biological control• reach a consensus amongst workshop participants on key principles that need to be considered in the prioritisation process of biological control targetsSuggestions made at the workshop are addressed in this report. Many of the concerns raised at the workshop corresponded with the common \u27core\u27 issues recorded in Paynter. These include concerns about lack of data, the tendency of the framework to overlook weeds outside the Weeds of National Significance, concerns that weightings are arbitrary, and a need for the framework to be able to anticipate emergent weeds and potential future problems. Here, those issues that are relevant to policy have been considered with the acknowledgement that remaining \u27core\u27 issues need to be addressed elsewhere

The prospect of biological control of Mimosa pigra with fungal pathogens in Australia

During surveys in Central and South America two fungal pathogens were identified as high-potential classical biological control agents for Mimosa pigra L. in Australia. The first, a wet-season fungus Phloeospora mimosae-pigrae H.C. Evans & G. Carrión, was released in Australia in 1994 and the second, the dry-season rust Diabole cubensis (Arthur & J.R. Johnst.), in 1996. Field observations in Central and South America and pre-release evaluations in England indicated promising impacts by the fungal pathogens as classical biological control agents, but both failed to establish long-term in Australia. The coelomycete anamorph (asexual form), P. mimosae-pigrae , was successfully mass-cultured in liquid medium and a standardised culturing and application protocol was developed and tested for large-scale field applications during the wet seasons from 1996 to 1998. The fungal pathogen established temporarily in the field and caused a considerable reduction in growth of mimosa seedlings. However, mature plants were less affected by P. mimosae-pigrae due to premature leaf-drop of diseased plant tissue. In addition, the fungal pathogen failed to develop its sexual form (teleomorph) in Australia, which is assumed vital for its survival. Post-release evaluation concluded that while P. mimosae-pigrae was unable to self perpetuate under the conditions in Australia, and thus was not suitable as a classical biological control agent, it has suitable characteristics and potential to be developed and used as a mycoherbicide for the control of mimosa. The environmental conditions in northern Australia also appeared to prohibit the longterm establishment of the dry-season rust D. cubensis. Mass-production of spores of the rust was labour intensive, yields were inconsistent and spores rapidly lost their viability. The rust caused disease symptoms on plants of mimosa after field inoculations but failed to spread and reinfect new growth of plants

Failure of Diabole cubensis, a promising classical biological control agent, to establish in Australia

The rust Diabole cubensis (Arthur & J.R. Johnston) Arthur was introduced into northern Australia as a classical biological control agent against the noxious wetland weed Mimosa pigra L. (Mimosaceae). Pre-release evaluation and observation in Mexico, Central America, and South America, the center of origin of D. cubensis, revealed a range of characteristics that suggested the rust had great potential to exert some control over M. pigra in Australia. This dry-season rust was cultured and field inoculations were carried out during the northern Australian dry season when ambient conditions were suitable for infection. Post-release assessments showed that M. pigra developed symptoms of rust infection in the field but that the rust failed to spread and therefore to establish in Australia. Analyses of the post-release assessments of D. cubensis in Australia pointed to gaps in the knowledge of the weed–pathogen ecology. The failure of the rust in light of performance of other biological control agents is reviewed

The key to success : an investigation into oviposition of the salvinia weevil in cool climate regions

In cooler climates of Australia, where salvinia (Salvinia molesta D.S.Mitchell (Pteridophyta: Salviniales) is rapidly becoming a major problem, long-term establishment of the salvinia weevil (Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae)) has not yet been achieved. Biological control appears to offer the only cost-effective and long-term solution to salvinia but until the agent is successfully established, ongoing use of expensive chemical and mechanical control methods are required. The reasons that the salvinia weevil is failing to establish in cool climates are not fully understood. This paper describes preliminary studies on oviposition of the salvinia weevil at low temperatures as part of an investigation into the breeding ability of the weevil in temperate zones. The effect of air and water temperatures on the oviposition of the weevil in climate-controlled cabinets, and a glasshouse has been investigated and results are discussed. In understanding cool temperature effects on oviposition of the weevil, a significant contribution could be made towards the long-term management of salvinia in temperate climates

Leaf and stem spot of Alternanthera philoxeroides (alligatorweed) in Australia caused by Nimbya sp.

This is the first report of Nimbya associated with alligator weed in Australia. Taxonomic studies and research into the use of Nimbya isolates for biological weed control are continuing