Natural Enemies from South Africa for Biological Control of Lagarosiphon Major (Ridl.) Moss Ex Wager (Hydrocharitaceae) in Europe
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by South East Academic Libraries System (SEALS) Hydrobiologia (2010) 656:149–158 DOI 10.1007/s10750-010-0427-0 AQUATIC WEEDS Natural enemies from South Africa for biological control of Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae) in Europe J.-R. Baars • J. A. Coetzee • G. Martin • M. P. Hill • J. M. Caffrey Published online: 13 September 2010 Ó Springer Science+Business Media B.V. 2010 Abstract The non-native invasive plant, Lagarosi- leaf damage despite high levels of parasitism by phon major (Hydrocharitaceae) is a submersed braconid wasps. Another yet unidentified fly was aquatic macrophyte that poses a significant threat to recorded mining the stem of L. major. Two leaf- water bodies in Europe. Dense infestations prove feeding and shoot boring weevils, cf. Bagous sp. difficult to manage using traditional methods. In (Curculionidae) were recorded damaging the shoot order to initiate a biocontrol programme, a survey for tips and stunting the growth of the stem. Several leaf- natural enemies of Lagarosiphon was conducted in feeding lepidopteran species (Nymphulinae) were South Africa. Several phytophagous species were frequently recorded, but are expected to feed on a recorded for the first time, with at least three showing wide range of plant species and are not considered for notable promise as candidate agents. Amongst these, importation before other candidates are assessed. The a leaf-mining fly, Hydrellia sp. (Ephydridae) that discovery of several natural enemies in the country of occurred over a wide distribution causes significant origin improves the biological control prospects of L. major in Europe. Guest editors: A. Pieterse, S. Hellsten, J. Newman, J. Caffrey, Keywords Hydrellia Á Bagous Á Leaf-mining fly Á F. Ecke, T. Ferreira, B. Gopal, J. Haury, G. Janauer, Phytophagous organisms Á Classical biological T. Kairesalo, A. Kanninen, K. Karttunen, J. Sarvala, control Á Native survey Á Ireland K. Szoszkiewicz, H. Toivonen, L. Triest, P. Uotila, N. Willby / Aquatic Invasions and Relation to Environmental Changes: Proceedings of the 12th International Symposium on Aquatic Weeds, European Weed Research Society Introduction J.-R. Baars (&) BioControl Research Unit, School of Biology and African curly leaved waterweed, Lagarosiphon major Environmental Science, University College Dublin, (Ridl.) Moss ex Wager (Hydrocharitaceae) (Oxygen Belfield, Dublin 4, Ireland weed, African Elodea) is a submersed non-native e-mail: [email protected] macrophyte found in several countries in Europe J. A. Coetzee Á G. Martin Á M. P. Hill (Symoens & Triest, 1983; Preston et al., 2002; Department of Zoology and Entomology, Rhodes Reynolds, 2002; Stokes et al., 2004; van Valkenburg University, Grahamstown, South Africa & Pot, 2007) and New Zealand (McGregor & Gourlay, 2002). It was first recorded in Ireland in J. M. Caffrey Inland Fisheries Ireland, Swords Business Campus, 1966 (Symoens & Triest, 1983) and has become Swords, Co. Dublin, Ireland noticeably invasive in the past decade. The discovery 123 150 Hydrobiologia (2010) 656:149–158 of substantial infestations in Lough Corrib in 2005 these and other submersed weeds, such as Cabomba has identified the need to control this species in caroliniana Gray, with surveys in the countries of Ireland (Gavin et al., 2007; Caffrey et al., 2008). Both origin revealing some promising candidate agents mechanical and chemical methods are used to control (Schooler et al., 2006). Prospects for the biocontrol of L. major with variable degrees of success (Caffrey L. major was considered for New Zealand, but no et al., 2008). However, the applications of such biological control programme was initiated as other control methods in environmentally sensitive areas aquatic plants were considered to be of higher pri- are unsustainable as a long-term solution since many ority (McGregor & Gourlay, 2002), and no natural herbicides are being de-registered and the application enemies were known from the region of origin of the of chemicals in waterways is considered unsuitable weed. However, as Sheppard et al. (2005) indicate, (see Water Framework Directive, CEC, 2000; Shaw, species like L. major may become suitable target 2007). Classical biological control in this case may species for biological control if we know more about provide an ideal strategy to control L. major in a the natural enemies in the country of origin. Indeed, a variety of freshwater habitats. short-term survey completed at two sites in South Invasive, free-floating and emergent aquatic weeds Africa recorded the presence of some natural enemies are amongst the weed species in Europe considered as on L. major (Schutz, 2007). good targets for classical biological control (Sheppard The genus Lagarosiphon is native to sub-Saharan et al., 2005). A number of the world’s worst aquatic Africa, and nine species are described with variable invasive species have been successfully controlled in distribution ranges throughout the continent including other parts of the world using biological control Madagascar (Wager, 1928; Symoens & Triest, 1983). (Cruttwell McFadyen, 1998; Charudattan, 2001; Hill, In southern Africa, Lagarosiphon muscoides Ridley 2003; McConnachie et al., 2004). The control of and L. major are the most common species encoun- submersed plants presents a particular challenge as tered, with most of the records of L. major occurring most biocontrol programmes have focused on terres- south of Zambia (from the South African Cape trial and free-floating aquatic plant invaders, with provinces to Zimbabwe). Both L. major and comparatively little attention given to submersed L. muscoides are considered noxious weeds in South plant species in the past. An exception is Hydrilla Africa (Obermeyer, 1964, 1966), and often prolifer- verticillata (L.f.) Royle, where two curculionid ate in man-made impoundments. As a result of the beetles Bagous affinis Hustache and Bagous hydrillae extensive natural distribution range in southern O’Brien, and two ephydrid flies Hydrellia pakistanae Africa, a short-term survey was conducted to deter- Deonier and Hydrellia balciunasi Bock were released mine the phytophagous organisms associated with as biocontrol agents in the United States (Balciunas L. major in particular. Results of this survey are & Burrows, 1996; Grodowitz et al., 1997; Julien & presented in this article, and the prospects of Griffiths, 1998). A native weevil Euhrychiopsis initiating a biological control programme in Ireland lecontei (Dietz) has also been used to control are discussed. Myriophyllum spicatum in northern United States and Canada (Julien & Griffiths, 1998; Johnson & Blossey, 2002). Many submersed weeds do present a Materials and methods significant threat to aquatic and riparian habitats (Charudattan, 2001) and warrant further attention, A field survey was undertaken in South Africa in despite a general lack of published information on the November 2008. Distribution records from the South natural enemies associated with submersed plants in African National Biodiversity Institute (Fig. 1) and the countries of origin (Bennett & Buckingham, 2000). published literature (Symoens & Triest, 1983)were Many species in the family Hydrocharitaceae, such as used to target localities where L. major had been Egeria densa Planchon, Elodea canadensis Michx, recorded, and priority was given to sites with recent Elodea nutallii (Planchon), and Hydrilla verticillata records. The survey included sites from some of are invasive in Europe (Preston et al., 2002; DAISIE, the most southerly records in Eastern Cape Province www.europe-aliens.org; Anonymous, 2009). Biolog- (*750 m a.s.l.) to high-altitude sites (1,400–2,000 m a.s.l.) ical control investigations have been initiated on in Mpumalanga Province. In suitable climatic areas, 123 Hydrobiologia (2010) 656:149–158 151 Fig. 1 Distribution records of L. major in South Africa from South African National Biodiversity Institute (SANBI) (open circles), and sites surveyed for L. major/L. muscoides (closed triangles). GT Gauteng, MP Mpumalanga, NP Northern, NW Northwest, KZN Kwa-Zulu Natal, EC Eastern Cape, WC Western Cape, NC Northern Cape, FS Free State, L Lesotho further impoundments were surveyed, and additional the bank occurring in less than 1.5-m depths, with site records held by Rhodes University were also some ponds only having a depth of about 0.5 m. visited. At each site, plants were assessed for damage Plants were accessible whilst wading, and all plant symptoms. Damaged plants were collected for dissec- parts were inspected (with less time spent on tion and the rearing of natural enemies. Arthropod rhizomes and roots). Sites surveyed included mostly specimens were assigned a Rhodes University acces- man-made dams and reservoirs, natural lakes and also sion number and sent to the South African National some rivers and streams. Stands of L. major ranged Collection of Insects (ARC-PPRI Pretoria) for identi- from small clumps amongst beds of L. muscoides fication. The plant material collected at each site was along the edges of dams, to large beds occupying the identified in the field using Cook (2004) and sent to entire water column of small impoundments. Lesley Henderson (Weeds Division, ARC-PPRI Pre- Hydro-chemical results served to characterise the toria) for confirmation of identification. At each site, sites, and some parameters are worth noting. hydrochemical parameters, including temperature Although temperature fluctuated