Search narrows for lippia biocontrol by lindayy


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                                                                                                                                       Rieks van        Louise
                                                                                                                                        Klinken        Lawrence
                                                                                                                                          for cSIrO eNtOMOlOgy

                                                                                                                              Lippia is a serious problem in
                                                                                                                              many parts of Australia, including
                                                                                                                              the vast Murray Darling Basin.
                                                                                                                              It has detrimental impacts on
                                                                                                                              agriculture and the environment.

   Search narrows for                                                                                                         But the prevalence of lippia
                                                                                                                              and the threat it poses could
                                                                                                                              soon be reduced significantly.

   lippia biocontrol
                                                                                                                              International researchers,
                                                                                                                              including CsIrO entomology

                                                                                                           CsIrO entomology
                                                                                                                              scientists, are narrowing their
                                                                                                                              search for an effective biological
                                                                                                                              control agent.

                                                         Farmers stand to benefit significantly                               Multiple problems
    Pest plant: Lippia is a problem plant for
    graziers as it can out-compete pasture
                                                         from an international research project that                            Lippia causes multiple problems. As well
    and force stocking rates to be reduced.              aims to identify an effective biocontrol agent                       as being unpalatable to stock, it forms a
                                                         for lippia, a potentially devastating weed that                      dense, smothering mat over large areas —
                                                         is highly prevalent in Australia.                                    preventing the growth of other plants, both
                                                                                                                              pasture and native. Floods spread lippia
                                                            Graziers in particular will welcome the
                                                                                                                              down waterways and allow it to colonise
                                                         progress being made in this quest, as lippia                         new areas.
                                                         can out-compete pasture and substantially
                                                         reduce stocking rates.                                                 Dealing with lippia can be difficult.
                                                                                                                              Mechanical and chemical means provide
     At a glance                                            Identifying a biocontrol agent will also                          short-term control, but biological control
                                                         lead to important environmental benefits.                            offers the most promise in the long-term.
    lippia is a serious problem                          Lippia can cause creek banks to collapse,                            The ultimate aim of such a project would be
    in areas that are periodically                       leading to problems such as erosion.                                 to reduce the weed to a level where it no
    flooded, such as in wetlands,                                                                                             longer posed a threat to livestock industries
                                                         Serious plant pest                                                   or the environment.
    floodplains and the riparian zone
    of waterways.                                                                                                             Native to the Americas
                                                         Introduced into Australia as a
    this weed costs livestock                                                                                                    Lippia and its close relatives are native to
    industries in the Murray Darling
                                                         low maintenance turf, lippia                                         the Americas, its distribution stretching
    Basin about $38 million a year.                      (Phyla canescens) is now a                                           from California to Argentina and Chile. The
                                                                                                                              search is now on in these areas for potential
    researchers are searching for                        serious weed in areas that                                           biocontrol agents and, to facilitate this,
    potential biological control agents                  are periodically flooded such                                        agreements are in place between CSIRO
    for lippia in the Americas, where                                                                                         and the United States Department of
    the plant is native.
                                                         as in wetlands, floodplains                                          Agriculture (USDA) and the University of
                                                         and the riparian zone of                                             Bahia Blanca, Argentina.
    lippia is likely to be a particularly
    stubborn problem in Australia,                       waterways, particularly in                                           International activity
    because of its rich genetic                          the Murray–Darling Basin.                                               Research on lippia is a truly international
                                                                                                                              activity. The Australian base is CSIRO
    diversity and ability to rapidly
    adapt to new conditions.                                                                                                  Entomology’s Long Pocket Laboratories in
                                                            It is a serious problem across 800,000
                                                                                                                              Brisbane, while the South American base
                                                         hectares of floodplain grazing country and                           for the search for insect natural enemies is
                                                         costs livestock industries in the Murray–                            at the USDA’s South American Biological
                                                         Darling Basin (MDB) about $38 million a                              Control Laboratory in Argentina. Surveys
                                                         year. But its distribution is much wider than                        for plant pathogens on lippia are being
                                                         that. It is found across five million hectares                       carried out at the University of Bahia Blanca
                                                         of the basin.                                                        and other trials are being carried out at

52 Farming Ahead October 2008 No. 201

                                                                                                                                                      of clones that originate from several different
                                                                                                                                                      native-range populations. This indicates
                                                                                                                                                      that lippia has been introduced to Australia
                                                                                                                                                      (and France) on multiple occasions, and that
                                                                                                                                                      the gene pools of introduced clones have
                                                                                                                                                      subsequently remixed.

                                                                                                                                   CsIrO entomology
                                                                                                                                                      growth and reproduction properties
                                                                                                                                                         Australian and French lippia populations
                                                                                                                                                      display different growth and reproduction
     Weed: Lippia can form a dense, smothering                                                                                                        properties to native populations in
     mat over large areas and prevent other plants                                                                                                    Argentina. Lippia can reproduce both
     from growing. Floods spread the weed down
                                                                     causing leaf damage on Phyla. Now, the                                           sexually (through the production of seeds)
     waterways. Lippia is a significant problem in
     the Murray Darling Basin.                                       researchers are developing propagation                                           and vegetatively (through runners that take
                                                                     methods and a proposal for host specificity                                      root at nodes). In general, French clones
                                                                     testing for one of the more promising                                            have thicker runners and wider leaves. This
    CSIRO’s European Laboratory at Montpellier                       rust fungi.                                                                      leads to a large ‘vegetative reproduction
    in France.                                                                                                                                        module’ that results in a rapid growth in the
                                                                     the effects of lippia on the environment                                         amount of plant matter present. On the
    In South America                                                    In order to determine how invasion by                                         other hand, Australian populations produce
       Although the native-range survey work                         lippia affects the soil carbon, water and                                        more flowers.
    for potential biocontrol agents is making                        nutrient pool in Australia, the team
    good progress, it is being complicated by the                    compared the presence of these components                                        rapid evolution
    fact that the classification of the complex of                   in lippia monocultures to those in uninvaded                                        This indicates a rapid evolution of lippia
    Phyla species is still not fully understood.                     grass communities.        This information,                                      after it has invaded the two countries. The
                                                                     together with additional studies on how the                                      divergent evolution of Australian and French
       The native-range survey work has found a                      physiology of the organism has adapted to
    wide range of insects and pathogens on                                                                                                            populations might be due to different
                                                                     the environment it is in, will help identify                                     selection pressures in the two countries.
    lippia. Now culturing methods for the most                       the aspects of lippia most vulnerable to
    promising are being developed in the                             attack by a biocontrol agent.                                                       In France, invaded habitats have been
    laboratory and preliminary host specificity                                                                                                       intensively managed and frequently
    testing has begun. This preliminary work                         High calcium concentration                                                       cropped, so larger ‘vegetative reproduction
    will help identify which potential agents                           Lippia tissues had a much higher calcium                                      modules’ might increase the survival and
    should be brought into quarantine in                             concentration than pasture grasses, much                                         regeneration rate of lippia after disturbances
    Australia for more thorough testing.                             of it present as calcium oxalate. This could                                     such as mowing and cultivation.
    Unravelling the Phyla complex                                    help explain why lippia is unpalatable to                                           Meanwhile, the high climatic variability
                                                                     cattle and other herbivores.           Being                                     in Australia might benefit clones that
       Several species of Phyla, as well as various
                                                                     unpalatable would favour lippia in heavily                                       respond rapidly to optimum growing
    intermediate forms, were found in
                                                                     grazed pasture.       In addition, calcium                                       conditions by producing flowers and seeds.
    Argentina. It was a complicated picture,
                                                                     carbonate crystals were found in cells on the
    which meant it was not always easy to
                                                                     leaf surface, which might also contribute to                                     Stubborn problem
    identify lippia plants. To help work out the
    real distribution of lippia, the researchers                     the plant’s defence against herbivores.                                             One preliminary conclusion from this
    are obtaining samples from as many                                                                                                                work is that lippia is likely to be a particularly
    locations and countries as possible.                             Compared with soil under                                                         stubborn problem in Australia due to its
                                                                                                                                                      rich genetic diversity and its apparent ability
       In order to select appropriate potential                      pastures, soil invaded by                                                        to rapidly evolve and adapt to new conditions.
    biocontrol agents, it is essential to
    understand the classification of the invasive                    lippia had significantly                                                         It is important that any biocontrol agents
    plant and its close relatives. Potential agents                  decreased soil moisture,                                                         chosen are effective on all Australian
                                                                                                                                                      genotypes or strains, as lippia not attacked
    might attack one species or variety, but
    not others, so researchers need to be sure
                                                                     generally lower soil pH and                                                      by the agents could be favoured.
    they are collecting from the right plants.                       higher electrical conductance                                                       Acknowledgements:        Australian       Wool
    The CSIRO team is collaborating with
    a geneticist at the University of New
                                                                     (possibly as a result of the                                                     Innovation, New South Wales Department of
                                                                                                                                                      Natural Resources (through the NSW Wetland
    England to try to unravel the complex of                         amount of sodium in infested                                                     Recovery Programme) and the Queensland
    Phyla species.                                                   soil) and lower nitrate-based                                                    Murray–Darling Committee are supporting
       While this will help untangle the various                                                                                                      this research. Meat and Livestock Australia
    closely-related Phlya species, it will not
                                                                     soil nitrogen.                                                                   and the Cooperative Research Centre for Weed
    answer the key question of whether the                                                                                                            Management are funding the genetics work at
    closely-related P. nodiflora, which is also                        Lippia infested soil also had significantly                                    the University of New England. Mic Julien,
    present in Australia, is a native. The answer                    lower organic carbon than the control soil,                                      Rieks van Klinken and Chengyuan Xu (CSIRO
    to that question will also affect which natural                  but there was no significant difference in                                       Entomology) in collaboration with Alejandro
    enemies could be considered as biological                        soil nitrogen.                                                                   Sosa (Buenos Aires), Guadalupe Traversa
    control agents.                                                  comparing lippia across countries                                                (University of Bahia Blanca, Argentina) and
                                                                                                                                                      Mohammad Fatemi (UNE) are carrying out
    Natural enemies                                                    Studies at CSIRO’s European and Long
                                                                                                                                                      the research.
      To date, 21 species of insects and mites                       Pocket laboratories and the University of
    have been found attacking lippia in South                        New England compared lippia populations
    America. Efforts are underway in Buenos                          in Australia, Argentina and France.                                               cSIrO research
    Aires to breed laboratory colonies of the                          The results showed that lippia populations
    most promising of these, while other species                     in invaded regions, such as Australia and                                         ContaCt Rieks van Klinken
    are still being identified. Meanwhile, the                                                                                                             (07) 3214 2761
                                                                     France, have similar genetic diversity to
                                                                                                                                                           (07) 3214 2881
    search for other potential agents continues,                     native-range populations in Argentina.
    mainly in Bolivia.       Several promising                       They also showed that each population in                                   
    pathogenic species of fungi were found                           the invaded regions is composed of a variety
           This article appeared in the October 2008 edition of the Kondinin Group’s monthly magazine Farming Ahead. The Kondinin Group holds the copyright on the article.
           Reproduction of this text in whole or part by any other publication or for any other purpose is not permitted without permission of the Farming Ahead editor.
           For more information contact the Kondinin Group on (08) 9478 3343.
54 Farming Ahead October 2008 No. 201

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