212Asparagus Workshop Part1.Indd

Plant Protection Quarterly Vol.21(2) 2006 63 National Asparagus Weeds Management Workshop Proceedings of a workshop convened by the National Asparagus Weeds Management Committee held in Adelaide on 10–11 November 2005. Editors: John G. Virtue and John K. Scott. Introduction John G. VirtueA and John K. ScottB A Department of Water Land and Biodiversity Conservation, GPO Box 2834, Adelaide, South Australia 5001, Australia. E-mail: [email protected] B CSIRO Entomology, Private Bag 5, PO Wembley, Western Australia 6913, Australia. Welcome to this special issue of Plant Pro- The National Asparagus Weeds Man- authors for the effort they have put into tection Quarterly, which details the current agement Committee (NAWMC) convened their papers and all the workshop par- state of Asparagus weeds management in the National Asparagus Weeds Manage- ticipants for their contribution. A special Australia. Bridal creeper, Asparagus as- ment Workshop in Adelaide, 10–11 No- thanks for workshop organization also paragoides (L.) Druce, is the best known vember 2005. The workshop was attended goes to Dennis Gannaway and Susan Asparagus weed and certainly deserves by 60 people including representation ex- Lawrie. its Weed of National Signifi cance (WoNS) tending from South Africa, through most status in Australia. However, there are regions of continental Australia, to Lord Reference other Asparagus species in Australia that Howe Island in the Pacifi c. The workshop Agriculture & Resource Management have the potential to reach similar levels was made possible with funding assistance Council of Australia & New Zealand, of impact as bridal creeper on biodiversity through the Australian Government’s Nat- Australia & New Zealand Environment (and hence their inclusion in the national ural Heritage Trust. This special double is- & Conservation Council and Forestry bridal creeper strategic plan [ARMCANZ sue of Plant Protection Quarterly contains Ministers (2001). ‘Weeds of National et al. 2001]). There is much to be gained the proceedings of the workshop, as well Signifi cance: Bridal creeper (Asparagus from sharing information and experiences as additional research and management asparagoides) strategic plan’. (National about the biology, ecology, impacts and papers on Asparagus weeds including the Weeds Strategy Executive Committee, control of all Asparagus weeds to advance review of bridal creeper for the Biology Launceston). their overall strategic management. of Australian Weeds series. We thank all found in Australia. In South Africa it is restricted to the winter rainfall region of Asparagus weeds in Australia – a South African the Western Cape. This form of the plant is a host for Zygina sp. and Eurytoma sp. perspective with emphasis on biological control and the tubers are damaged by weevil prospects larvae, but Crioceris sp. and P. myrsiphylli were not recorded. Carien A. KleinjanA,B and Penny B. EdwardsA,C Potential taxonomic difficulties of A CSIRO Biological Control Unit, Zoology Department, University of Cape some of the other Asparagus spp. that occur in Australia are discussed, and pre- Town, Private Bag, Rondesbosch, 7701, South Africa. B liminary observations are provided on Current address: Zoology Department, University of Cape Town, Private their associated natural enemies in South Bag, Rondebosch, 7701, South Africa. e-mail: [email protected] Africa. C Current address: PO Box 865, Maleny, Queensland 4552, Australia. Keywords: Asparagus, Asparagus asparagoides, Australia, biological control, Criocer- is, environmental weed, Eurytoma, natural Summary released in Australia against the first enemies, Puccinia, South Africa, Zygina. The results of an extensive South African form which has a wide distribution in survey to identify potential biological South Africa. No candidate was found Introduction control agents for Asparagus asparagoides that damages the tuber system of this South Africa supports a wealth of Aspara- are discussed. Two forms of A. aspara- form of A. asparagoides, but foliage dam- gus species with several endemic to the re- goides were found that are distinguished age reduced tuber mass and fruit produc- gion. The most recent taxonomic revision of by characteristics of the tuber system. tion under experimental conditions. The South African plants recognized 81 species, Not all the natural enemies found in as- seed wasp Eurytoma sp. occurs through- of which only 15 are recorded as occurring sociation with A. asparagoides attacked out the distributional range of this form naturally beyond the borders of southern both forms. Three biocontrol agents (Zy- of A. asparagoides. Damage levels vary Africa (Obermeyer et al. 1992). The higher gina sp., Crioceris sp. and Puccinia myr- but can be 90% or more. The second form taxonomy of Asparagus spp. has tended to siphylli) from South Africa, have been of A. asparagoides has only recently been oscillate between the recognition of one and 64 Plant Protection Quarterly Vol.21(2) 2006 three genera. Obermeyer recognized three specimens. Based on the observed dis- Impact of foliage feeding on fruit genera: Myrsiphyllum (with 12 species in tributions of the two forms of the plant, production and tuber mass South Africa), Protasparagus (with 69 spe- Kleinjan and Edwards (1999) refer to The agents released to date all target the cies in South Africa) and Asparagus (with one form of the plant as the ‘widespread foliage of the widespread form of A. as- no South African species). However, all form’ of A. asparagoides, which has a wide paragoides. It was hoped that a potential species are currently considered members distributional range in South Africa. The agent would be identifi ed that directly of a single genus, Asparagus (Malcomber second form is restricted to the western damages the tuber system of the plants, and Sebsebe 1993, Fellingham and Meyer Cape and is referred to as the ‘West- but despite intensive searching no such 1995). ern Cape form’ of A. asparagoides. These candidate was found. However, substan- The Asparagus species considered a same terms are used throughout this tial outbreaks of Zygina sp. had been noted threat in Australia (Asparagus asparagoides text. in the aseasonal rainfall region and con- (L.) Druce, Asparagus scandens Thunb., As- Asparagus asparagoides specimens from sequently an experiment (Kleinjan et al. paragus declinatus L., Asparagus plumosus Australia were compared against both 2004) was conducted with Zygina sp. to Baker, Asparagus densifl orus (Kunth) Jessop forms of this species from South Africa explore the impact of foliage damage on and Asparagus africanus Lam.) occur natu- and were found to be consistent with the tuber growth. As reduced fruit loads were rally in South Africa, but only A. aspara- ‘widespread form’ (Kleinjan and Edwards recorded subsequent to the Zygina sp. out- goides has been surveyed comprehensively 1999). In 2004 it was discovered that the break, the experiment also investigated for natural enemies for use in a biological ‘western Cape form’ of A. asparagoides is the impact of foliage damage on fruit pro- control program. also present in Australia. duction. The results showed that exten- This paper reports on the surveys con- sive foliage damage substantially reduced ducted on A. asparagoides in South Africa The widespread form of Asparagus both fruiting and fi nal tuber mass. The ex- and provides incidental observations of asparagoides in South Africa perimental design made it impossible to the natural enemies associated with the Distribution and habitat associations determine whether the impact of Zygina other species of concern in Australia, with The widespread form of A. asparagoides oc- sp. caused a reduction in the rate of tuber the exception of A. africanus for which no curs in the winter, summer and aseasonal mass accumulation or whether it caused a information is available. (i.e. the rainfall is not restricted to any par- reduction in existing tuber reserves. Morin ticular season) rainfall regions of South Af- et al. (2002) demonstrated experimentally Asparagus asparagoides rica (Kleinjan and Edwards 1999). In the that infection of the widespread form of Taxonomy and distribution of A. winter rainfall region, ripe fruits develop A. asparagoides with P. myrsiphylli similarly asparagoides in November and the plants subsequently resulted in a reduction in tuber number, Soon after surveys for natural enemies of senesce completely. Production of new rhizome length and shoot mass. A. asparagoides were initiated in South Af- shoots starts well ahead of the next rainy rica during 1988, problems were encoun- season. In the aseasonal rainfall region Natural enemies that attack seed or fruit tered with the distribution records for this ripe fruits also develop in November, but As Asparagus species are bird dispersed, species. Published distribution records for vegetative parts of the plants are present a reduction in seed output could be pre- A. asparagoides proved to be misleading throughout the year, with an approximate- dicted to decrease the rate of colonization and required reassessment. Our surveys ly annual turnover of stems. The situation of new sites and may reduce the rate at showed that A. asparagoides does not occur in the summer rainfall region is unclear which infestations develop. Two natu- in subtropical coastal regions and the arid due to infrequent surveys in the area. ral enemies (Zalaca snelleni (Wallengren) interior and west coast regions of South However, it appears that most plants

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