International Weed Biocontrol Symposium
In March around 155 weed biocontrol practitioners from 24 countries descended on Kruger National Park, South Africa, for the 14th International Symposium on Biological Control of Weeds (ISBCW).
Despite the drawcard location, the number attending was down on previous events, as around the world the current economic climate is requiring most science organisations to reduce expenditure. However, for those who were able to attend, the symposium was a memorable experience, and as always was an important forum for refining international best practice and developing new collaborations. Since classical weed biocontrol projects always involve an overseas component of work, and weeds come from all over the globe, international collaboration is critical. The symposium is normally held every 4 years, but was moved a year forward this time to coincide with the 100-year anniversary of weed biocontrol in South Africa (see South Africa Scores a Century). We have another 11 years to go in New Zealand before we hit this milestone.
Although New Zealand is a small country, with a modest budget for weed biocontrol, it continues to more than hold its own on the international stage, and our people were again given a number of speaking slots. Lynley Hayes chaired the first session of the conference, which dealt with exploring new biological control possibilities. This session included 3 oral papers and 12 rapid-fire poster presentations – a good way of covering a lot of material in a short time! On day two Mike Cripps (AgResearch) spoke about recent breakthroughs in working with the rust Puccinia punctiformis on Californian thistle (Cirsium arvense) (we covered this story in Issue 64 of this newsletter). We also heard that CABI China have undertaken surveys in northwest China, an area that has previously received little attention, to look for additional potential biocontrol agents for Californian thistle. They have found a fungus, Pustula spinulosa, that they believe offers potential. This white blister rust attacks the leaves, stems and flowers, and preliminary host-testing suggests it might be suitable for New Zealand if additional agents are required (provided our populations prove to be susceptible). Next Hugh Gourlay outlined the international effort to develop biocontrol for tutsan (Hypericum androsaemum) in New Zealand (covered in Issue 66). Earlier we heard from Elena Olsen, the student attached to CABI-Switzerland who has been undertaking surveys to look for potential biocontrol agents for tutsan in Europe. She reported that none of the additional strains of the tutsan rust (Melampsora hypericorum) found in Europe to date appear to offer better control options for North Island tutsan populations, which appear to have some resistance to them. So, for now, insect agents appear to offer the best prospects for improving tutsan control. After the conference we heard that the Tutsan Action Group has been successful in their application to the Ministry for Primary Industries’ Sustainable Farming Fund for support to test, import and release potential new tutsan agents.
On day three Quentin Paynter gave two papers. In the first Quent shared his newly created risk index, which will hopefully in the future be able to assist regulatory authorities to assess the risk of approving new agents that show some ability to potentially use non-target plants (see Data Diving Provides Pearls of Wisdom). Later that day Quent presented data showing that broom (Cytisus scoparius) seeds in New Zealand are substantially bigger on average than broom seeds in Europe, and as a consequence broom seed beetles (Bruchidius villosus) are also larger in New Zealand. We will explain what these findings mean for broom biocontrol in the next issue of this newsletter. Also, Simon Fowler gave a paper outlining the discovery of Liberibacter in broom in New Zealand (which we covered in Issue 64) and subsequent research that has determined this disease likely came in with the broom psyllid (Arytainilla spartiophila). The consequences of the introduction of this disease to New Zealand are still being evaluated but fortunately do not appear to be serious. However, this discovery will have ongoing ramifications for the use of phloem-feeding insects like psyllids. Molecular tools are now available to detect whether potential biocontrol agents are carrying unwanted organisms like Liberibacter, which could potentially be transferred and cause harm to other hosts. However, it remains to be seen if it would be possible to rid the insects of their unwanted companions and make them safe to release. Finally on day three, Sarah Dodd, en route to Ghana to undertake African tulip tree (Spathodea campanulata) surveys, outlined the new 5-year programme to develop biocontrol for serious weeds in the Cook Islands (covered in Issue 67).
On the final day of the conference Ronny Groenteman spoke about her work to determine whether St John’s wort beetles (Chrysolina spp.) provide effective control of St John’s wort (Hypericum perforatum) (see Whodunnit? Solving the Case of the Disappearing St John’s Wort).
Overall there were mixed feelings about how biocontrol is going worldwide. In South Africa and Europe biocontrol is booming. South Africa has overcome regulatory issues experienced during the 2000s, and the European Union, after years of being uncertain how to deal collectively with invasive species or regulate biocontrol activities, is now getting its act together. Other countries like Brazil are taking the first steps towards developing their own weed biocontrol projects, after years of assisting other countries to find agents for weeds of Brazilian origin. Developing countries like Indonesia are also keen to explore biocontrol opportunities. However, other countries like Australia, the USA, and those in east Africa are struggling with capacity, funding or regulatory issues. Australia at the height of its weeds research capacity in the 1980s and 1990s had around 30 scientist FTEs and is now down to just 7.5. The retirement of a number of key scientists (some of whom paid their own way to attend the symposium), the ending of the Weeds Co-operative Research Centres, disinvestment in the Weeds of National Significance Scheme and winding back of the National Weeds Strategy, plus a succession of conservative governments, combined with less enthusiasm for environmental projects and less familiarity with biocontrol by regulators, have all taken their toll. The loss of skills and capacity in Australia is serious and likely to result in an increased need to pool resources and rely on the efforts of other countries. New Zealand currently appears to be holding its own, producing excellent underpinning science and developing many new agents, ably supported by an excellent regulatory system and some very supportive end-users. But funding remains tight and is not guaranteed, and we need to remain on our guard that our capacity to undertake weed biocontrol is not gradually eroded.
Below are some summaries of projects of special interest to New Zealand.
Fireweed (Senecio madagascariensis)
Fireweed is widespread in New Zealand and beginning to cause concern in some areas such as Northland. The plant is referred to here as gravel groundsel (S. skirrhodon) but the taxonomy is complex and not totally resolved. The S. madagascariensis complex may include S. skirrhodon. A molecular study needs to be undertaken to clarify the identity of New Zealand material, and seeds have been sent to South Africa for this purpose. New Zealand also has native Senecio species so highly specific agents would be needed here too. The seeds sent to South Africa will also be used in a common garden experiment comparing introduced (Australian, New Zealand) and native (South African) fireweed populations. This will explore whether there has been a trade-off between growth and dispersal ability against competitiveness and resistance to herbivory (which is hypothesised to result in the rapid evolution of invasiveness). Experiments will also test the efficacy of potential agents. Preliminary results suggest that natural enemies in South Africa are putting some pressure on the plant.
Lagarosiphon (Lagarosiphon major)
Researchers from the Biocontrol Research Unit, University College Dublin, made a number of presentations on their work to develop biocontrol for lagarosiphon (Lagarosiphon major) in Ireland. The most promising agents they have identified include a leaf-shredding moth (probably Synclita sp.), a shoot-mining midge (Polypedilum sp.), and a leaf-mining fly (Hydrellia lagarosiphon), none of which have been released yet. Studies have been undertaken to see how complementary these three agents might be. These studies showed that fly larval survival was negatively impacted by the moth but not the midge. The fly and the midge appear to have a synergistic effect resulting in cumulative damage. Since lagarosiphon is a serious aquatic weed in New Zealand there is considerable interest in developing the fly and midge for release here as funds permit. The Irish researchers recently agreed to undertake some testing to see if the leaf-mining fly would be suitable to release in New Zealand, which is expected to be completed mid-year. They have studied the best way to rear this fly as they were finding egg production to be quite low when methods developed for other Hydrellia flies (used as biocontrol agents for Hydrilla verticillata), involving artificial diets, were used. By experimenting with the components of artificial diets they have come up with a mixture that increases the development and reproduction rates of the fly, allowing the flies to be produced much more quickly and cheaply.
Mexican devil weed (Ageratina adenophora)
Montpellier broom (Genista monspessulana)
Montpellier broom (Genista monspessulana), also known as Cape or French broom, forms dense infestations in southern Australia, western North America, Chile and South Africa. While not a major weed in New Zealand currently, there are warning signs that Montpellier broom could become more problematic in coming decades. An accidentally released psyllid (Arytinnus hakani) is providing impressive control of Montpellier broom in Australia. CSIRO reports that all stands where the psyllids were released have been decimated, and within a year typically only a few small debilitated plants remain. Once the psyllid has been distributed to all remaining infestations in Australia it is expected that Montpellier broom will be under complete control. In light of the research showing that the broom psyllid (Arytainilla spartiophila) brought a species of Liberibacter with it to New Zealand, it would be important to show that the Montpellier broom psyllid had no similar association if introduction to New Zealand is considered down the track. Because of concerns that the psyllid could damage native lupins it is not being considered for release in North America, and a weevil (Lepidapion argentatum) that attacks the seeds and forms stem galls is being studied instead.
New World Catalogue
The last (5th) version of Julien and Griffiths’ A World Catalogue of Agents and Their Target Weeds was published in 1998. For many years this was the go-to place to find out what weed biocontrol agents have been released around the world and how successful they have been, but had become seriously out of date. During the past 4 years a team of researchers, led by Rachel Winston, has undertaken a major revision and expansion of this catalogue, which now includes 224 weeds and 552 agents. This was a huge task. Funding was mostly provided by the United States Department of Agriculture’s Forest Service. A full online version of the catalogue is expected to be available in June (www.ibiocontrol.org), including a fully query-able database. A shorter print version is also being prepared. Ways to keep the information maintained and up to date are being considered. Note that all previous ISBCW proceedings have been scanned and are now available on this website.