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Control of wild kiwifruit (Actinidia species) in bay of plenty New Zealand
Abstract
A large population of wild kiwifruit, mostly Actinidia deliciosa, has grown in the Bay of Plenty region of New Zealand over the past 30 years, fueled by the increasing commercial success of kiwifruit production. This fast-growing non-native woody vine has invaded native forest and scrub and commercial Pinus radiata plantations. The environmental impacts of wild Actinidia have led it to be listed as a Total Control Pest Plant in the Environment Bay of Plenty Regional Pest Management Strategy. Wild vines can be reliably killed with any of sprayed Tordon® Brushkiller (picloram/triclopyr), Grazon® (triclopyr) and stump treatment with Vigilant ™ gel (picloram). $NZ523,000 was spent from 1998 to 2005 on controlling wild Actinidia in the Bay of Plenty, funded by partnerships between the kiwifruit industry and Environment Bay of Plenty. The four control seasons of 2001/2002 through to 2004/2005 more than 21,000 vines have been killed. Similar control efforts each season have found progressively fewer vines (almost 6000 fewer vines in 2004/2005 than 2001/2002), indicating that the population is being successfully reduced. Between 67% and 96% of the pre-control population of established wild vines are estimated to have been removed. Sustained control over several more years will be required to reduce this population to an easily manageable size. This is complicated by continued recruitment into the wild population from commercial crops, principally via birds feeding on reject kiwifruit fed out to farm stock. We suggest that other countries that commercially propagate wild kiwifruit outside of its native range take care to prevent wild populations from establishing in surrounding vegetation.
... Invasive woody species present in seed rain (such as shade-tolerant Ligustrum lucidum and L. sinense that formed a dense understorey in some older plantings) are capable of displacing native canopy species (Smale & Gardner 1999;Vidra et al. 2007). The smothering lianes Lonicera japonica and Hedera helix were widespread in seed rain, while Leycesteria formosa, Rubus fruticosus and Actinidia deliciosa were found to form persistent soil seed banks -the former two able to produce dense stands impenetrable to native species (McQueen 1993) and the latter able to invade closed-canopy forest (Sullivan et al. 2007). Tradescantia fluminensis was the dominant groundcover in several restoration forest patches, and although spread by vegetative growth rather than seed, this weed species colonised several seed-rain trays during this study, displaying an ability to quickly form a mat capable of suppressing the establishment of native seedlings (Whaley et al. 1997;Standish et al. 2001). ...
Restoration of native forest vegetation in urban environments may be limited due to isolation from native seed sources and to the prevalence of exotic plant species. To investigate urban seed availability we recorded the composition of seed rain, soil seed banks and vegetation at native forest restoration plantings up to 36 years old in Hamilton City and compared these with naturally regenerating forest within the city and in a nearby rural native forest remnant. Seed rain, soil seed banks (fern spores inclusive) and understorey vegetation in urban forest were found to have higher exotic species richness and lower native species density and richness than rural forest. Both understorey vegetation and soil seed banks of urban sites >20 years old had lower exotic species richness than younger (10–20 years) sites, indicating a developmental threshold that provided some resistance to exotic species establishment. However, the prevalence of exotic species in urban seed rain will allow reinvasion through edge habitat and following disturbance to canopy vegetation. Persistent soil seed banks from both urban and rural sites were dominated by exotic herbaceous species and native fern species, while few other native forest species were found to persist for >1 year in the seed bank. Enrichment planting will be required for those native species with limited dispersal or short-lived seeds, thus improving native seed availability in urban forests as more planted species mature reproductively. Further research into species seed traits and seedling establishment is needed to refine effective management strategies for successful restoration of urban native forests.
Actinidia (Kiwifruit) is a diverse genus of dioecious, generally deciduous, climbing plants. Currently, 55 species and about 76 taxa
are recognized within the genus. The genus has a wide geographic distribution in eastern Asia, from just south of the Equator,
to as far north as latitude 50○. The basic chromosome number of Actinidia is x = 29. Polyploidy in Actinidia is common, with diploids, tetraploids, hexaploids, and octoploids occurring in diminishing frequencies. Kiwifruit in comparison
with most other crop plants have a very short history of cultivation. The two commercially important kiwifruit species, Actinidia deliciosa and A. chinensis, were introduced into cultivation in the last 110 years. Almost all current kiwifruit cultivars are either direct selections
from the wild or only a few generations removed from the wild. There are also many traits within non-cultivated Actinidia species that could have commercial potential if transferred into cultivated kiwifruit. By incorporating fruit traits such
as different colors, ripening indicators, edible or peelable skins, different flavors, and nutrient compositions into the
currently cultivated species, there is potential to develop many new kiwifruit cultivars. We describe studies using both cultivated
plants and their wild allies on the origin, evolution, phylogenetic relationships, cytogenetics, and the genetic improvement
of kiwifruit employing both classical strategies and advanced tools of genomics and biotechnology.
Biosecurity politics in New Zealand is implicated in the constitution of a new dimension of citizenship, a biosecure citizenship. This form is distinct in that the political determinants of citizenship do not fully rest on the individual body, but on the body’s connections to other entities, the inter- and intra-active symbiotic condition of human-non-human ‘living together’. Through its constitutive role in enabling the ‘dangerous’ mobility of pathogens, viruses and invasive species, symbiotic individuality has become politicised as a matter for state determination and control. Contemporary articulations of biosecure citizenship emphasise a variety of contractual and non-contractual responsibilities, which augment the national coordinates of citizenship, reconstitute symbiotic individuality, and justify the state penetration of the private sphere. Drawing on biosecurity legislation, public education campaigns and research with community weed removal projects, I chart the reinforcement and practice of this biosecure citizenship. I argue that there is an urgent need to democratise decisionmaking about the construction of biological threat, about where and how to make cuts in our symbiotic associations with different species, and between species and spaces. By articulating biosecure citizenship not only as a discourse of ecological responsibility but of rights, biosecurity could be reinvigorated as ‘bios-security’, the inclusive politics of continually questioning the ecological good life.
The two commercially most important kiwifruit species worldwide are Actinidia chinensis and A. deliciosa. Both species are native to China: A. chinensis grows more in the lowlands in the more eastern provinces towards the coast, A. deliciosa in the western, inland, colder areas. Large quantities of kiwifruit are collected from wild vines although this resource is threatened because of the methods of harvesting. Commercial cultivation of kiwifruit in China started only 20 years ago and by 1998 there were c. 45 000 ha of kiwifruit orchards, 75% in cultivars of A. deliciosa, 25% in cultivars of A. chinensis. About one third of the total plantings are in Shaanxi province. Many different cultivars of A. chinensis and A deliciosa have been selected but 12 of these, together with ‘Hayward’ from New Zealand, account for nearly 85% of the total area planted in kiwifruit in China. These cultivars are described. The A. deliciosa cultivar ‘Qinmei’ is the most widely planted, c. 40% of the total area. Average yields per hectare are still low and most plants are either young or have not even started cropping. In 1998 the total production of kiwifruit from China was 118 500 t, and in 1999 c. 165 000 t, two thirds of which came from Shaanxi province. Almost all the kiwifruit produced are sold within China and, to date, only small quantities are exported. Within a few years China will be producing much more kiwifruit from commercial orchards than any other country and this is likely to have a significant impact on international trade in kiwifruit.