Weed Biocontrol Symposium

The XI International Symposium on the Biological Control of Weeds, hosted by CSIRO Entomology, was held at the Australian National University in Canberra, Australia from 27 April to 2 May 2003. This 4-yearly symposium series provides one of the most important forums for scientists working in this field of research dealing with the ecology of invasive weeds and the use of arthropods and pathogens to control their spread, as well as with the ethics and risks associated with the overall concept of biological control. The Canberra meeting was attended by about 220 delegates from around the world. Australia, New Zealand, South Africa and the United States were strongly represented but there were also a number of absences due to the recent Iraq war and SARS. The overall emphasis of the conference lay on the importance of ecology as the underlying discipline for biological control. The conference was divided into five main themes: biocontrol theory and new approaches, target and agent selection, risk analysis, integration and management, and evaluation. Fifty-eight talks and 122 posters were presented.

The keynote speech by Donald Strong (University of California, USA), opening the theme 'theory and new approaches', gave a general insight into how future biological control needs to diversify as a discipline encompassing not only life but also social sciences. The other topics addressed during this session were the new encounter concept as a potential strategy for weed biocontrol using plant pathogens (Harry Evans, CABI Bioscience , UK); the necessity to test climate compatibility of biological control agents in order to predict their establishment and performance in the area of introduction (Marcus Byrne, University of the Witwatersrand, South Africa) and the potential influence of interactions between insect and fungal agents on various aspects of biological control of weeds e.g. agent selection and effectiveness (Richard Hill, New Zealand).

The theme 'target and agent selection' was introduced by Peter McEvoy (Oregon State University, USA) stressing the importance of looking at critical attributes of enemies, weeds and environment as well as identifying crucial stages in the weed's life cycle in order to avoid introduction of non-effective control agents. The majority of talks presented in this session were entomologically orientated, although a pathology paper presented by Carol Ellison (CABI Bioscience, UK) looked at the significance of intraspecies pathogenicity in the selection of a pathotype of the rust Puccinia spegazzinii for classical biological control of mile-a-minute weed (Mikania micrantha) in Southeast Asia (see `Can the `Green Tidal Wave' of Asia Be Curtailed?', General News, this issue).

The theme `risk analysis' was divided into three sessions. Criticism of weed biocontrol usually focuses on the danger of biocontrol agents attacking species other than the target weed. Hence, the talks presented generally dealt with how to minimize such risks, e.g. through rigorous refined specificity testing procedures, or how to assess and weigh the risk associated with the use of biocontrol agents. An example of how to assess and manage the risk of using the non host-specific pathogen Sclerotinia sclerotiorum was presented from New Zealand (Graeme Bourdôt) where the extent of safety zones around biocontrol sites were estimated based on models of escape and aerial dispersion of its spores. Lars Baker (Wyoming Counties, USA) gave an interesting talk on the impact of leafy spurge biological control agents on non-target spurges. Although the introduced leaf beetles fed on the indigenous spurge, which occurred in the same habitat, they preferred the target weed, which they controlled, and the net effect was for the indigenous spurge to become more common. This was picked up by Tony Willis who pointed out very clearly that in evaluating the risk that biological control agents present to indigenous plants, the fact that a biological control agent may feed on an indigenous species is not critical, but it is the impact on that indigenous plant which needs to be evaluated. Jim Cullen picked up in this in his concluding presentation (see below) and it is a message that needs to reach biocontrol's customers and the public.

Many talks presented within the theme `integration and management' gave overviews of individual biological control programmes and extension work as the socioeconomic dimension. Overall release strategies of agents were also frequently addressed as for example in the paper given by Alana Den Breeÿen (Plant Protection Research Institute (PPRI), South Africa). The speaker documented the release strategies adopted for Mycovellosiella lantanae var. lantanae against Lantana camara in South Africa using a combination of isolates to target a wide range of L. camara biotypes in the field as well as releasing them over a range of environmental conditions.

The last main theme addressed different aspects of evaluating weed biological control. Cheryl Lennox (PPRI, South Africa) presented the success story of the Australian gall rust Uromycladium tepperianum released into South Africa in 1987 against the invasive shrub Acacia saligna which is now considered to be under complete biological control. Jane Barton (New Zealand) reported that in plot experiments in New Zealand control of the Central American weed Ageratina riparia using the introduced white smut Entyloma ageratinae benefited the native vegetation rather than, as often feared, other weedy exotics, while the last speaker of the symposium, Andrew McConnachie (University of the Witwatersrand, South Africa), put some hard figures on the successful biological control of Azolla filiculoides in South Africa with a calculated benefit-cost ratio of 2.5:1 for 2000 and a forecasted ratio 15:1 by 2010.

Several workshops were organized by individual delegates including:

'Assessment of biological risk factors associated with the use of exotic organisms in containment facilities' (Glynn Maynard, Office of the Chief Plant Protection Officer, Department of Agriculture, Forestry & Fisheries - Australia (OCPPO/AFFA), Australia). This workshop was organized in order to obtain scientific input from biocontrol practitioners into the policy document currently being drawn up by the OCPPO.

'Where biocontrol is heading in the 21st century' (Rachel McFadyen, Cooperative Research Centre (CRC) for Australian Weed Management). Discussions during this workshop raised a number of issues, which need to be addressed within the context of biological control in the future e.g. the need to select and breed better agents; the issues of genetically modified agents; acceptance of test results from other countries; studies of interactions between agents, weed and native biodiversity; increased legislative problems; inter-country movement; more emphasis on economic issues; future job prospects for researchers. Suggested actions that need to be taken included targeting stakeholders, promoting integrated weed management, promoting internationally agreed testing protocols for insect and pathogens acceptable to regulators and raising the awareness about success stories in weed biocontrol.

'Centres of origin' (Alec McClay, Alberta Research Council, Canada) provided a forum for emphasizing the difficulties in identifying centres of origin.

Jim Cullen (CSIRO, Canberra) closed the symposium on Friday afternoon giving an overall synthesis of the meeting. He pointed out the complexity of the systems biological control of weeds has to deal with, the significant progress which has been made in many areas, but also the attention which is needed with respect to the socioeconomic context, economic evaluations and the predictability of control measures.

This report is adapted from a report written by Marion Seier (CABI Bioscience) for BSPP News, the newsletter of the British Society for Plant Pathology, which funded her attendance at the symposium.

www.bspp.org.uk/

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Bioherbicide Workshop

The VI International Bioherbicide Workshop, 'Bioherbicides: The Next Generation' was held on 27 April 2003, immediately before the XI International Symposium on the Biological Control of Weeds, at the Australian National University in Canberra, Australia. The workshop, which constitutes the forum of the International Bioherbicide Group, was organized by Maurizio Vurro, Bari, Italy and was attended by some 35 scientists working in the field of mycoherbicides who gave 17 oral and 3 poster presentations.

The workshop explored the possibilities and constraints of using plant pathogens in an inundative approach to control weeds, particularly with a view towards the future of bioherbicides. Four invited speakers, Raghavan Charudattan (University of Florida, USA), Alan Watson (McGill University, Canada), Ken-ichi Yamaguchi (Minami-Kyushu University, Japan) and David Sands (Montana State University, USA) set the scene discussing what traits would be desirable for future bioherbicides, how their efficacy could be enhanced, why overall bioherbicides had only limited success and which factors influence the biopesticide market in Japan. Following on from this several papers presented case studies looking at certain aspects regarding the control of specific weeds with individual biocontrol agents, as well as new research into formulation and application of plant pathogens aiming to overcome environmental constraints. Particularly interesting was a paper by Charudattan and co-workers, reporting on the discovery of tobacco mild green mosaic tobamovirus (TMGMV) causing a systemic, hypersensitive response in and, thus, killing tropical soda apple (Solanum viarum), a highly invasive weed in the southeastern United States. Should current attempts to develop and register TMGMV be successful this would constitute the first virus-based bioherbicide. [See also BNI 24(2), 31N-32N (June 2003), Tropical soda apple biocontrol bears first fruit.]

The general discussion at the end explored new concepts for bioherbicides, for example formulating cocktails of different plant pathogens effective against several weeds or using strains of plant pathogens capable of producing phytotoxic amino acids. Options for applying plant pathogens, highly virulent but exhibiting less host specificity, were also discussed. Finally, the necessity of choosing the right organisms and the right market niche in order to develop a successful bioherbicide was stressed.

This report was written by Marion Seier (CABI Bioscience) for BSPP News , the newsletter of the British Society for Plant Pathology, which funded her attendance at the symposium.

www.bspp.org.uk/

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Chromolaena Workshop

The 6th International Workshop on Biological Control and Management of Chromolaena odorata was organized by the Chromolaena Working Group, hosted by Dr. R.N. Muniappan (University of Guam), under the auspices of the International Organization for Biological Control of Noxious Animals and Plants (IOBC), with sponsorship from IOBC Asia & Pacific Regional Section and the Australian Centre for International Agricultural Research (ACIAR). It was attended by some 30 scientists from Australia, East Timor, Fiji, Guam, Indonesia, Micronesia, Papua New Guinea (PNG), South Africa and the UK.

This Workshop is held every 3-4 years to discuss current research on the biological control and management of the invasive alien weed Chromolaena odorata. Indonesia was originally chosen as the venue but for security and logistical reasons, this was moved to Cairns.

Rachel McFadyen, recently appointed as Chief Executive Officer for Australian Weed Management (CRC), opened the workshop with a history of the research on biological control of chromolaena weed which started with her work on insect natural enemies at CIBC (Commonwealth Institute of Biological Control, now part of CABI Bioscience ) in Trinidad in the mid-1960s, with funding from the Nigerian Oil Palm Research Institute. Since then, this neotropical plant has become an extremely problematic invasive weed not only in West Africa but also in Southern Africa and throughout tropical Asia and the Pacific Islands. At the last Workshop, held in Durban (South Africa) in October 2000, it was recommended that chromolaena weed should now be adopted to replace the out-dated and misleading old name Siam weed.

Since this pioneering research by CIBC, most of the research efforts have continued to be directed at arthropod natural enemies, with some work on fungal pathogens being undertaken by South Africa supplemented by unfunded inputs from CABI Bioscience . This was reflected in the presentations most of which concentrated on projects or programmes funded by the US Department of Agriculture and ACIAR (Australian Centre for International Agricultural Research) to introduce and establish two insect agents from Trinidad, the arctiid moth Pareuchaetes pseudoinsulata and a tephritid gall fly Cecidochares connexa in the Asian and Pacific Regions. Successful control of the weed was first achieved in Guam with the moth but control elsewhere has largely been ineffective and the evaluation of other arthropod agents has continued in both Asia and South Africa, the former funded by ACIAR because of concerns about its continued spread through Southeast Asia and the Pacific islands and the threat posed to Australia.

Successful control seems also to have been achieved in Indonesia and parts of PNG with a combination of the moth and gallfly. However, the search for additional natural enemies is continuing in the Americas, mainly involving South African scientists, for those areas where the gallfly is ineffective, either through parasitism or climatic unsuitability. An excellent study by Costas Zachariades and co-workers (Plant Protection Research Institute, South Africa) detailed the search for the origins of the distinctive South African biotypes; using biogeographical, morphological and molecular evidence, which strongly suggests that it was introduced from the northern Caribbean region. This explains why both insect and fungal natural enemies from South and Central America have proven to be ineffective against the South African biotype and why recent collections from Cuba and Jamaica are showing promise.

A CABI Bioscience paper, delivered by Harry Evans was the only one out of the 20 presented which dealt with fungal biocontrol agents. The main emphasis of the paper was on the related weed Mikania micrantha, and considerable interest was expressed in the CABI biocontrol project in India since this weed is becoming a serious invader in many countries of the Australasian-Pacific region and has recently been recorded in northern Australia. Amongst the recommendations made at the closing session was that the scope of the Workshop should be broadened to include all invasive Eupatorieae ( Ageratina, Ageratum, Austroeupatorium, as well as Chromolaena and Mikania), and that new research initiatives to assess additional natural enemies, including fungi, should be encouraged in countries having problems with invasive Eupatorieae. Barbara Waterhouse (Australian Quarantine and Inspection Service, AQIS) gave a comprehensive overview of the Australian efforts under the Northern Australian Quarantine Strategy (NAQS) to prevent invasive weeds from reaching tropical Australia, and the costly efforts by the Australian peace-keeping forces in Southeast Asia to de-contaminate military equipment.

Owen Zeimer (Centre for Wet Tropics Agriculture, Queensland) presented a detailed report on the nationally-funded campaign to eradicate C. odorata and M. micrantha , which were first detected in northern Queensland in the early 1990s. Chromolaena odorata has proven to be the more widespread, and hence more problematic weed, and an intensive programme involving cultural practices, herbicide application and controlled burning has been on-going for the past 5-6 years. A field visit to these sites followed to appreciate at first-hand the difficulties of topography and logistics which are involved in any eradication campaign.

The concluding papers described potential new biocontrol agents of C. odorata and new weed problems involving species of Eupatorieae . Of interest and no little concern, is that a defoliating butterfly (Actinote) is being considered for release in China, despite the fact that the host range is relatively wide, including both Chromolaena and Mikania. Broadening of the Workshop terms of reference, to include all invasive Eupatorieae, appears, therefore, to be propitious, especially since a new invasive weed, Praxelis (Eupatorium) clematidea , closely related to C. odorata , has recently been identified in northern Australia and is also invading southern China and Taiwan.

By: Harry Evans, CABI Bioscience

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