Devitalisation of imported horsetail (Equisetum hyemale)

This art icle was downloaded by: [ Unit ec NZ I nst it ut e of Technology] On: 18 February 2013, At : 21: 29 Publisher: Taylor & Francis I nform a Lt d Regist ered in England and Wales Regist ered Num ber: 1072954 Regist ered office: Mort im er House, 37- 41 Mort im er St reet , London W1T 3JH, UK New Zealand Journal of Crop and Horticultural Science Publicat ion det ails, including inst ruct ions f or aut hors and subscript ion inf ormat ion: ht t p: / / www. t andf online. com/ loi/ t nzc20 Devitalisation of imported horsetail (Equisetum hyemale) M. F. Large a , D. J. Blanchon b & M. L. Angus b a School of Nat ural Sciences, Unit ec New Zealand, Privat e Bag 92 025, Auckland, New Zealand E-mail: b School of Nat ural Sciences, Unit ec New Zealand, Privat e Bag 92 025, Auckland, New Zealand Version of record f irst published: 22 Mar 2010. To cite this article: M. F. Large , D. J. Blanchon & M. L. Angus (2006): Devit alisat ion of import ed horset ail (Equiset um hyemale) , New Zealand Journal of Crop and Hort icult ural Science, 34: 2, 151-153 To link to this article: ht t p: / / dx. doi. org/ 10. 1080/ 01140671. 2006. 9514400 PLEASE SCROLL DOWN FOR ARTI CLE Full t erm s and condit ions of use: ht t p: / / www.t andfonline.com / page/ t erm s- and- condit ions This art icle m ay be used for research, t eaching, and privat e st udy purposes. Any subst ant ial or syst em at ic reproduct ion, redist ribut ion, reselling, loan, sub- licensing, syst em at ic supply, or dist ribut ion in any form t o anyone is expressly forbidden. The publisher does not give any warrant y express or im plied or m ake any represent at ion t hat t he cont ent s will be com plet e or accurat e or up t o dat e. The accuracy of any inst ruct ions, form ulae, and drug doses should be independent ly verified wit h prim ary sources. The publisher shall not be liable for any loss, act ions, claim s, proceedings, dem and, or cost s or dam ages what soever or howsoever caused arising direct ly or indirect ly in connect ion wit h or arising out of t he use of t his m at erial. New Zealand Journal of Crop and Horticultural Science, 2006, Vol. 34: 151-153 0014-0671/06/3402-0151 © The Royal Society of New Zealand 2006 151 Short communication Downloaded by [Unitec NZ Institute of Technology] at 21:29 18 February 2013 Devitalisation of imported horsetail (Equisetum hyemale) M. F. LARGE D. J. BLANCHON M. L. ANGUS School of Natural Sciences Unitec New Zealand Private Bag 92 025 Auckland, New Zealand email: [email protected] Abstract Equisetum hyemale is a popular import for use in floristry. Anecdotal evidence from florists suggested, that despite Ministry of Agriculture and Forestry (MAF) requirements to devitalise imported plant material, Equisetum stems remain viable and readily form roots when placed in water or fioristry foam. Imported stem material was tested and confirmed as being capable of producing roots and shoots. Fresh material of Equisetum was treated using the devitalisation techniques prescribed by MAF and was killed. Discrepancies are noted between the importation requirements for the United States versus Australasian material. Keywords horsetail; Equisetum hyemale; fioristry; biosecurity; devitalisation; glyphosate; foliage INTRODUCTION Most species of Equisetum (horsetail) are recorded as having the potential to become persistent weeds, particularly in areas where rainfall exceeds 500 mm per annum. Holm etal. (1977) rank horsetails among the world's worst agricultural weeds because of their resilience, toxicity, and ability to dominate poorly drained land. International experience suggests control of well-established plants is difficult because H05112; Online publication date 12 April 2006 Received 21 September 2005; accepted 28 February 2006 of the presence of deep, underground rhizomes (Holm et al. 1977; Csurhes & Edwards 1998). Equisetum is a genus of some 30 species and includes several putative hybrids (Csurhes & Edwards 1998). These plants are perennial with underground rhizomes and jointed aerial stems. Leaves are usually inconspicuous and encircle the nodes in a fused toothed sheath. Depending on species, stem height may range from 5 cm to 6m. Reproduction is by spores or by rhizome. The genus Equisetum has a wide distribution, being found throughout most of the Northern Hemisphere temperate regions in swamp and open grassland. E. arvense L. is native to Europe, Asia, and North America, but has naturalised in Madagascar, South Africa, South America, Australia, and New Zealand. In New Zealand, this species has been recorded from sites throughout the country (Webb et al. 1988). The arrival of E. arvense in New Zealand, along with a second species E. hyemale L, has variously been attributed to spores or rhizome portions being attached to other plants, and to importation of material for garden cultivation. The New Zealand adventive distribution for E. hyemale is summarised in Webb et al. 1995. Biosecurity New Zealand (of the Ministry of Agriculture and Forestry (MAF)) has included this species on the national plant pest accord and declared it to be an unwanted organism. The implication of this declaration is that propagation, sale, and distribution of the species within New Zealand are prohibited. Despite weed status in many regions of the world, various species of Equisetum have found favour as garden plants, and are used in homeopathic medicine, herbal teas (Csurhes & Edwards 1998), and in fioristry. In New Zealand, the fioristry industry buys imported E. hyemale stems, which are used for formal and corporate designs. Material is reportedly sourced from the United States and Australia. The presence of spore-filled cones on the imported product varies and even when present, are usually removed by florists after purchase, as they are considered to detract from the clean straight form of the stems. Downloaded by [Unitec NZ Institute of Technology] at 21:29 18 February 2013 152 New Zealand Journal of Crop and Horticultural Science, 2006, Vol. 34 Equisetum destined for New Zealand is airfreighted within 24 h of harvest. Floristry material arriving from Australia is listed as propagable (as per appendix 1, MAF Biosecurity Authority (Plants) Standard 152.09.05, 155.02.04) and must be devitalised. However, material from the United States is regarded as not propagable (see appendix 1 MAF Standard 152.09.05). Consequently this material is not devitalised. MAF standard 152.09.05 lists an approved devitalisation treatment option where stems are immersed for 20 min in a solution of 0.05% Roundup® (2-phosphonomethylamino) acetic acid, as 360g/litre glyphosate). Anecdotal evidence from florists suggested that despite these precautions, Equisetum stems readily form roots when placed in water or in floristry foam. MATERIALS AND METHODS Viability of imported material Equisetum stems were sourcedfrom three commercial flower wholesalers in 2004 and 2005. Unfortunately, the origin of this material is not clear, with stems imported from both the United States and Australia. For commercial reasons, further details were not available. Ten stems were cut in in half (stems are often cut for use), placed in tap water, and kept at room temperature. Where present, cones were removed. After 3 weeks, resulting plants were potted up in standard potting mix. Cones and spores All available cones (12 total) were removed and the spores extracted. Two samples were prepared from each cone using sucrose buffer and Fluorescein diacetate (after Heslop Harrison & Heslop Harrison 1970) and examined under a Zeiss fluorescent microscope (see Large & Braggins 1991 for discussion of sample size and extraction techniques). Spore samples from each cone were cultivated on nutrient agar in both light and dark conditions. Devitalisation trial Equisetum stems were obtained from material previously cultivated in standard potting mix for 6 months. Stems were then treated as per the approved devitalisation treatment option 1 (MAF standard 152.09.05). Stems were immersed for 20 min in a solution of 0.05% Roundup® (360g/litre glyphosate). Each stem was dried in air then placed in tap water. As a control, stems were taken fresh from the plant and placed directly in water without glyphosate treatment. Both treated and control stems were placed in a culture room with cool, white fluorescent lights (16h light/8 h dark) at 24°C for 2 weeks and checked daily. RESULTS Viability of imported material All 20 of the original imported samples rooted from the nodes within 7-10 days when placed in tap water. Basal material was absent in all instances and appears to be unnecessary for propagation. Rooted stems continued to grow, developing new cones within 4 months of first being placed in water. A voucher specimen (Unitec 001539) was prepared and is held in the Herbarium, School of Natural Sciences, Unitec New Zealand. Cones and spores In all samples (N = 1200, mean = 76% range = 74-87%) of spores were found to be alive as shown by reaction to Fluorescein diacetate. Despite the relatively high percentage of living spores, cultivation on agar was unsuccessful with no sign of germination or gametophyte development after 6 months. Although spores were initially alive, actual fertility and capacity for gametophyte grown is still unknown. Devitalisation trial Stems treated with glyphosate, as per the approved MAF standard, showed signs of yellowing within a week of treatment and did not produce roots. Within 2 weeks stems were completely yellow and were beginning to show signs of decay. Control stems not treated with glyphosate remained green and all produced roots and shoots from the nodes. DISCUSSION Where required, devitalisation is supposed to be carried out in the exporting country. Despite an additional declaration to the phytosanitary certificate and a requirement for viability testing, there is always a chance that material is not treated as prescribed by MAF Biosecurity. Furthermore, it seems illogical that material from Australia be regarded as propagable and subjected to devitalisation, whereas seemingly equivalent stems from the United States are not. Given the limited information available concerning provenance of the material studied, it is conceded Downloaded by [Unitec NZ Institute of Technology] at 21:29 18 February 2013 Large et al. — Devi tali sati on of imported horsetail that all stems may have originated from the United States, hence they may not have been devitalised at all. In any event this study suggests that imported Equisetum is not subjected to effective devitalisation. It poses a threat to New Zealand in the event that unwanted material is dumped into the wild or propagated in a garden. The presence of cones on imported material is a further matter for concern. Although spore germination and gametophyte growth was not recorded in this study many (76%) of the spores were apparently living. Wind dispersal of spores thus remains a potential risk pathway. When applied, the approved devitalisation (that being immersion in 0.05% Roundup® (glyphosate at 360 g per litre) is successful in preventing root growth. Unfortunately this treatment also results in relatively rapid yellowing of the material and thus may compromise the use of the plants by the floristry industry. Anecdotally, some Equisetum material has been found to have a short vase life and decomposes rapidly on arrival in the country. This had previously been assumed to be because of the age of the material, but may be the result of treatment with glyphosate. It may be useful to trial lower concentrations of glyphosate to determine if it is possible to devitalise the stem material without appreciably reducing vase life. Glyphosate has been shown to have little effect when used as a spray for control of E. arvense in Sweden. Torstensson & Borjesson (2004) found that its use seemingly led to an increase in the prevalence of this weed species and they suggested that imazapyr may be used as an alternative to glyphosate. It may be feasible to try this alternative herbicide to devitalise Equisetum material, although its effectiveness on this species needs to be determined, as do appropriate concentrations, which will not reduce vase life. CONCLUSION Given the success demonstrated in this study in growing imported Equisetum stems and the results from the devitalisation trial using glyphosate, we may conclude that: (1) stems are not being treated properly; or (2) all stems are from the United States and not treated. Further study is required on material that is known to have originated in Australia. In any event it is apparent that standards aimed at preventing the cultivation of Equisetum stems are inadequate and that there is a requirement for viability testing at the border. The reclassification of material from the United States as propagable and imposition of a devitalisation process deserves consideration as does a search for alternative treatments. ACKNOWLEDGMENTS We thank the external referees along with Jane Harman, Bill Bussell, and Ingrid Ennis, Unitec, for reviewing this manuscript. REFERENCES Csurhes S, Edwards R 1998. Potential environmental weeds in Australia. Queensland, Queensland Department of Natural Resources. 152 p. Heslop Harrison J, Heslop Harrison Y 1970. Evaluation of pollen viability by enzymatically induced fluorescence: intracellular hydrolysis of fluorescein diacetate. Stain Technology 45: 115-120. Holm LG, Plucknett DL, Plancho JV, Herberger JP 1977. The world's worst weeds: distribution and biology. Honolulu, The University Press of Hawaii. 609 p. Large MF, Braggins JE 1991. Spore atlas of New Zealand ferns and fern allies. Supplement to the New Zealand Journal of Botany. Wellington, SIR Publishing. 167 p. MAF Bio security Authority (Plants) Standard 152.09.05 2002. Clearance of fresh cut flowers and foliage. Wellington, Ministry of Agriculture and Forestry. 25 p. MAF Bio security Authority (Plants) Standard 155.02.042002. Import health standard for cut flowers and foliage. Wellington, Ministry of Agriculture and Forestry. 20 p. Torstensson L, Borjesson E 2004. Use of imazapyr against Equisetum arvense on Swedish railway tracks. Pest Management Science 60: 565-569. Webb CJ, Sykes WR, Garnock-Jones PJ 1988. Flora of New Zealand, Volume IV: Naturalised Pteridophytes, Gymnosperms, Dicotyledons. Christchurch, Botany Division, DSIR 1365 p. Webb CJ, Sykes WR, Garnock-Jones PJ, Brownsey PJ 1995. Checklist of dicotyledons, gymnosperms, and pteridophytes naturalised or casual in New Zealand; additional records 1988-1993. New Zealand Journal of Botany 33: 151-182.