African Boxthorn (Lycium Ferocissimum) and Asset Protection from a National Perspective

Nineteenth Australasian Weeds Conference African boxthorn (Lycium ferocissimum) and asset protection from a national perspective Michael Noble1, Robin Adair2 and Alan Yen3 1 Department of Primary Industries, Parks, Water and Environment, PO Box 303, Devonport, Tasmania 7310, Australia 2 Australis Biological, PO Box 151, Bittern, Victoria 3918, Australia 3 Department of Environment and Primary Industries and School of Applied Systems Biology, La Trobe University, 5 Ring Road, Bundoora, Victoria 3083, Australia ([email protected]) Summary African boxthorn (Lycium ferocissimum fly (Bactrocera tryoni Froggatt), and potentially the Miers), a Weed of National Significance, is widespread tomato potato psyllid (Bactericera cockerelli Sulc) in southern Australia. Development of a national should it enter Australia. African boxthorn has a sig- strategy, biological control feasibility assessment, nificant presence in southern Australia’s agricultural and a national best practice manual for boxthorn led areas. to the identification of key areas to guide investment. In 2012, African boxthorn was declared a Weed of With a weed as widespread as African boxthorn National Significance (WoNS). Following WoNS dec- in Australia, asset protection is the priority for man- laration, an African boxthorn national strategic plan, agement, along with provision of additional tools for feasibility of biological control of African boxthorn management of a widespread weed. initial assessment and African boxthorn national best This paper outlines three key areas where man- practice manual have been produced. The strategic agement investment for African boxthorn in Australia plan outlines national priorities for the strategic man- might be made. These are: biodiversity-rich areas of agement of African boxthorn in Australia. Western Australia where boxthorn has significant Widespread weeds like boxthorn can be difficult invasive potential; horticultural regions susceptible to direct expenditure toward, as priorities are often to pest species hosted by boxthorn; and boxthorn difficult to pinpoint. Using the biosecurity continuum biocontrol research. (AWC 2013), asset protection and building manage- Keywords African boxthorn, Weeds of National ment capability are logical investment approaches Significance, biodiversity, horticulture, biological for African boxthorn in much of southern Australia. control. This paper looks at three specific areas of importance for the national management of African INTRODUCTION boxthorn. These are the ongoing expansion and impact African boxthorn has been present in Australia for potential of African boxthorn in ecologically rich more than 150 years and is one of Australia’s most southern Western Australia, the potential of African widespread weeds. It occurs across a diverse range of boxthorn as a host for horticultural pests in areas Australian landscapes from coastal to semi-arid inland with solanaceous crops, and the potential of classical habitats, and is present in many of Australia’s most biological control to provide an additional African important environmental and agricultural asset areas. boxthorn management tool. In Australia, boxthorn impacts World Heritage listed places (e.g. Shark Bay in Western Australia and WESTERN AUSTRALIAN LANDSCAPES the Lord Howe Island Group in New South Wales), In Western Australia, unlike most other suitable parts Ramsar-listed wetlands (e.g. Pitt Water – Orielton La- of Australia, African boxthorn has not fully expanded goon in Tasmania and the Coorong in South Australia), throughout its potential range. This may be linked to internationally and nationally recognised biodiversity the relationship between boxthorn and the starling hotspots, and many of the nation’s most significant (Sturnus vulgaris). Evidence from Bass Strait (Harris offshore island environments. and McKenny 1999) and New Zealand (Taylor 1968) African boxthorn hosts a range of pest animals suggests that starlings boost boxthorn’s capacity to including rabbits (Oryctolagus cuniculus Linnaeus), invade natural environments, and in turn, boxthorn foxes (Vulpes vulpes Linnaeus), feral pigs (Sus scrofa provides quality roosting and feeding habitat for Linnaeus), starlings (Sturnus vulgaris Linnaeus), fruit starlings. The pest species’ appear to have facilitative 231 Nineteenth Australasian Weeds Conference interactions. The starling is so far absent (other than reaching Australia in the near future. In North America, occasional incursions) from Western Australia. its overwintering host plants are several native Lycium The virtual absence of starlings in Western species (Butler and Trumble 2012). The TPP is a major Australia permits greater potential for containment pest of solanaceous crops such as tomatoes, potatoes, of boxthorn, so far preventing it from establishing a capsicum, egg plants and tamarillos because it is the foothold throughout important natural assets, despite vector of the plant bacteria, Candidatus Liberibacter being present around them. solanacearum Jagoueix et al., the causative agent of The establishment of starlings in Western Australia the so-called zebra chip disease. would almost certainly result in increased invasive The TPP is reputed to have over 40 host plant spe- capacity of boxthorn in natural ecosystems. cies, primarily in the Solanaceae family (Biosecurity Western Australia has substantial environmental Australia 2009). It was recently found to use African assets of national and global significance. In the south- boxthorn as an overwintering host plant (Fowler 2013), ern half of the state, boxthorn poses a direct threat to and is able to breed on that host species (J. Dohmen, some of these. For example, on the South Coast the Fitz- pers. comm. 2013). TPP populations build up on their gerald River Ravensthorpe region provides habitat for over wintering hosts, and they colonise commercial an extraordinary number of nationally listed threatened crops in spring. The sizes of TPP populations can be species (more than 40 species of fauna and over 100 reduced if access to overwintering host plant species flora species) (Gilfillan et al. 2009). The area holds a is reduced; hence the importance of controlling Af- United Nations designation of ‘Fitzgerald Biosphere’, rican boxthorn near susceptible horticultural crops. containing two internationally listed wetlands, and Another danger is the possible transfer of Candidatus having immense overall species richness – making it Liberibacter solanacearum to native Australian plant a biodiversity hotspot. species by any native Australian psyllids that may feed The presence of African boxthorn on off-shore on plants with this disease. Acizzia solanicola Kent & islands in Western Australia appears to be increasing. Taylor is a native Australian psyllid that has switched African boxthorn continues to threaten, for example, from its native solanaceous plant species to egg plants Australian sea lion (Neophoca cinerea Peron) and (Taylor and Kent 2013). Australian fur seal (Arctocephalus pusillus Schreber) breeding habitats through displacing the native nitre BIOLOGICAL CONTROL bush (Nitraria billardieri DC.) that shelter sea lion and African boxthorn is difficult to suppress using seal pups. Boxthorn does not provide the equivalent mechanical and chemical control methods due to a quality of nursery habitat to that provided by nitre persistent seed bank, strong re-colonisation capacity bush, leaving pups more vulnerable to predation and expense. Although African boxthorn has been sug- (Moritz and Kikkawa 1994). gested as a target for biological control (Julien 2006), In 2013 Western Australia’s South Coast NRM Australia is the only region where this approach is completed a substantial African boxthorn management being considered. In 2013, the potential for biological program. Other Western Australian initiatives have control was formally evaluated and considered to be included the state’s Department of Parks and Wildlife feasible (Adair 2013). recent undertaking of African boxthorn management In Australia, a low diversity and abundance of on the Beagle Islands south of Geraldton. These islands natural enemies from African boxthorn are known. provide some of the most important sea lion breeding In a recent survey, only 12 species of arthropod and habitat on the Western Australian coastline. pathogen were recorded from south-eastern Australia, Follow-up of initial boxthorn control measures is but it is likely additional taxa could be recorded with essential to successful management. It is very impor- more extensive searches. tant that ongoing investment be made to continue and Similarly, in southern Africa, only five arthropods extend this strategically important work in Western and one pathogen are recorded from L. ferocissimum, Australia. but a richer assemblage is known from other Lycium species elsewhere indicating that the low diversity is IMPLICATIONS FOR HORTICULTURE perhaps an artefact of limited survey and collection Boxthorn hosts a range of agricultural pests including effort in the region of origin. Biological surveys on the fruit fly (Bactrocera tryoni) and the tomato potato other large, woody African shrubs (e.g. boneseed psyllid (TPP) (Bactericera cockerelli). The latter is Chrysanthemoides monilifera subsp. monilifera (L.) a North America species that has spread to Central Norlindh and myrtle-leaf milkwort Polygala myrti- America (Davidson et al. 2008). It has not been found foilia L.), show a richer assemblage of phytophagous in

Load more