5,152 results for Lincoln University

  • Ecological and pest-management implications of sex differences in scarab landing patterns on grape vines

    González-Chang, M.; Boyer, S.; Lefort, Marie-Caroline; Nboyine, Jerry; Wratten, Stephen D.

    Journal article
    Lincoln University

    Background: Melolonthinae beetles, comprising different white grub species, are a globally-distributed pest group. Their larvae feed on roots of several crop and forestry species, and adults can cause severe defoliation. In New Zealand, the endemic scarab pest Costelytra zealandica (White) causes severe defoliation on different horticultural crops, including grape vines (Vitis vinifera). Understanding flight and landing behaviours of this pest can help inform pest management decisions. Methods: Adult beetles were counted and then removed from 96 grape vine plants from 21:30 until 23:00 h, every day from October 26 until December 2, during 2014 and 2015. Also, adults were removed from the grape vine foliage at dusk 5, 10, 15, 20 and 25 min after flight started on 2015. Statistical analyses were performed using generalised linear models with a beta-binomial distribution to analyse proportions and with a negative binomial distribution for beetle abundance. Results: By analysing C. zealandica sex ratios during its entire flight season, it is clear that the proportion of males is higher at the beginning of the season, gradually declining towards its end. When adults were successively removed from the grape vines at 5-min intervals after flight activity begun, the mean proportion of males ranged from 6-28%. The male proportion suggests males were attracted to females that had already landed on grape vines, probably through pheromone release. Discussion: The seasonal and daily changes in adult C. zealandica sex ratio throughout its flight season are presented for the first time. Although seasonal changes in sex ratio have been reported for other melolonthines, changes during their daily flight activity have not been analysed so far. Sex-ratio changes can have important consequences for the management of this pest species, and possibly for other melolonthines, as it has been previously suggested that C. zealandica females land on plants that produce a silhouette against the sky. Therefore, long-term management might evaluate the effect of different plant heights and architecture on female melolonthine landing patterns, with consequences for male distribution, and subsequently overall damage within horticultural areas.

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  • The locus for an inherited cataract in sheep maps to ovine chromosome 6

    Wilson, Gareth R. S.; Morton, James D.; Palmer, David N.; McEwan, J. C.; Gately, Karl; Anderson, R. M.; Dodds, K. G.

    Journal article
    Lincoln University

    Purpose: Cataracts are an important cause of blindness in humans but there are few large animal models available. One of these animal models is Ovine Heritable Cataract, a bilateral cortical cataract which develops after birth. This cataract has been used as a model for human cataracts in drug trials, but the gene responsible for the cataract trait is unknown. A genetic test for cataract would improve the efficiency of the model by predicting which animals would develop cataracts. Identifying the genetic basis of the cataract would indicate its relevance to human cataract. Methods: A genome scan was performed on 20 sheep chromosomes, representing 86% of the genome, to determine the position of the cataract locus. Additional microsatellite markers were tested on chromosome 6 using a larger pedigree. Fine mapping was performed using a breakpoint panel of 36 animals and novel microsatellite markers taken from the bovine genome assembly. All exons of the candidate gene nudix (nucleoside diphosphate linked moiety X)-type motif 9 (NUDT9) were sequenced in normal and affected sheep. Results: Significant linkage was found between cataract status and markers on chromosome 6. Linkage analysis on the larger pedigree showed the most likely position of the cataract locus was between 112.3 and 132.9 cM from the centromere. During fine mapping, NUDT9 was considered as a positional candidate for the cataract gene because it was located within the linked interval and is expressed in the lens. The gene was ruled out as the cataract gene after extensive genotype analysis, but a single nucleotide polymorphism (SNP) inside it provided a useful restriction fragment length polymorphism (RFLP) marker for further fine mapping. Twelve new markers were found and used to map the cataract locus to between 131.1 and 131.8 cM from the centromere. Conclusions: A region of ovine chromosome 6 strongly linked to cataract has been identified, and a genetic test for cataract based on a SNP within this region has been developed. The best candidate gene within this region is AF4/FMR2 family, member 1 (AFF1), the mouse equivalent of which is associated with an inherited cataract.

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  • Internationalisation of Indonesian SMEs

    Revindo, Mohamad Dian

    Thesis
    Lincoln University

    Indonesia faces rapid changes in its international trade policies and environment owing to its engagement in various bilateral, regional and multilateral free trade agreements. Free trade escalates business competition for small and medium-sized enterprises (SMEs) in the domestic market through cheap imported products and the increasing operation of foreign enterprises, but offers enormous opportunities for SMEs to export and venture abroad. However, Indonesian SMEs are less able to take advantage of foreign market opportunities than their large counterparts and only account for a small share of Indonesia’s non-oil and gas exports, contradicting their important contribution to business establishment, employment provision and value added creation. This study analyses the internationalisation of Indonesian SMEs, with focus on their direct-export activities. In particular, the study examines the characteristics of exporting and non-exporting SMEs in terms of export stimuli, export barriers, network relationships and participation in government’s export assistance programmes. The study investigates the strategies and processes undertaken by SMEs to become exporters along with the factors influencing SMEs’ export engagement, the determinants of SMEs’ export intensity and the factors influencing SMEs’ performance improvement due to export engagement. The policy measures to foster SMEs’ exports are formulated based on the research results. Primary data was obtained from survey questionnaires administered in April-August 2014 to SMEs in seven provinces in Java, Madura and Bali regions and central government agencies whose policies are related to SMEs and/or international trade. The survey yielded a response rate of 53.76% and 497 usable responses, including 271 exporting SMEs and 226 non-exporting SMEs. Descriptive statistics were used to distinguish the characteristics of exporting and non-exporting SMEs. Principal component analysis was used to reduce the dimensions of export stimuli and export barriers. The empirical frameworks include binary logistic regression to estimate the determinants of SMEs’ export engagement and fractional logit regression to estimate the determinants of SMEs’ export intensity and exporting SMEs’ performances. The descriptive statistics results show that SMEs are stimulated to export because they aspire to find new markets, but they initiate export activities because of the presence of foreign buyers. SMEs plan to begin exporting to neighbouring countries but they, in reality, initiate export to large and high income countries. SMEs’ timing to become exporters varies across provinces. Exporting SMEs in Bali and Yogyakarta, two main tourist destination provinces, on average take less time to internationalise from the outset, indicating a born global firm phenomenon probably due to high exposure to foreigners. The estimation results show that SMEs’ propensity to engage in export activities is influenced by the international work experience of the owners/managers, product, location, firm age, firm size, central government assistance, network relationships with non-government actors and their perceptions of export barriers. SMEs’ export intensity is affected by the international work experience of the owners/managers, location, firm age, firm size, export experience, export market, central government assistance, network relationships with non-government actors and their perceptions of export barriers. Engaging in export activities may improve SMEs’ performances, but the performances are influenced by owners/managers’ education level, firm size, export experience, export intensity, the presence of foreign investors and SMEs’ participation in central government’s export assistance programmes. SMEs encounter various export barriers at pre-exporting and exporting stages. At the pre-exporting stage, SMEs are less likely to engage in export activities if they perceive difficulties in tariff and non-tariff barriers, informational and human resource barriers, distribution, logistics and promotional barriers, business environment barriers in host countries, procedural barriers, and foreign customer and competitor barriers. At the exporting stage, SMEs are prevented from sustaining and developing their exports mainly by informational and human resources barriers, distribution, logistics and promotional barriers, financial barriers, foreign government barriers, procedural barriers and price barriers. However, the policy makers and the SMEs have different perceptions on the severities of each type of export barrier. The results provide new evidence on firm internationalisation theories, namely the Uppsala Model, the Network Model, the Resource-Based View and the International New Venture Theory. The results give insight for the policy makers seeking to identify potential exporters, develop effective assistance to remove the main export barriers and strengthen the function of internationalisation networks. The results also provide insights for SMEs’ managerial teams to enable the speeding up of their internationalisation process.

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  • Nitrification inhibition by common plants in New Zealand’s agricultural landscapes

    Downward, Rachel Lilian

    Thesis
    Lincoln University

    Author known by the later name: Rachel Fields

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  • Causes of elevated coumestrol in lucerne and mitigation of the subsequent risk to ewe reproductive performance

    Fields, Rachel Lilian

    Thesis
    Lincoln University

    Author known by previous name: Rachel Downward

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  • Changes in trypsin inhibitory activity of developing seed parts and pod of red kidney bean

    Alizadeh, Hossein; Leung, D.; Edwards, Y.

    Conference Contribution - Published
    Lincoln University

    Mature red kidney bean seeds contain bovine trypsin inhibitors (TI) that could limitdigestion of proteins by insects, animals or human beings. The changes in trypsin inhibitory activity of red kidney bean seed parts and pods in relation to the different stages of seed development (10 to 50 days after flower fall) were investigated using a spectrophotometric method. Specific activities of bovine trypsin inhibitor in all the different tissues increased from early on during seed development. Those in the seed pod decreased to very low levels at seed maturity suggesting that they might not be deleterious to animal nutrition as far as TI content is concerned. The high level of trypsin inhibitors found in developing seeds would be of concern from the perspective of animal or human nutrition.

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  • How value chains can share value and incentivise land use practices: a white paper

    Saunders, Caroline M.; Dalziel, Paul C.; Wilson, Mark M. J.; McIntyre, Tiffany; Collier, H.; Kaye-Blake, William H.; Mowat, A.; Olsen, T.; Reid, John D.

    Report
    Lincoln University

    This white paper was commissioned by the Our Land and Water National Science Challenge to test the hypothesis that the more collaborative a value chain is, the greater is the value that New Zealand producers, processors and manufacturers in the land and water sector can capture from profiling the desirable ‘credence attributes’ of its production systems (‘the New Zealand story’), targeted at consumer segments. The analysis in this paper draws on the published results of the MBIE-funded research programme, Maximising Export Returns, and a structured literature review based on the keywords “market orientation of value chains” and “food”.

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  • Susceptibility of four grapevine rootstocks to Cylindrocladiella parva

    Brown, Dalin S.; Jaspers, Marlene V.; Ridgway, Hayley J.; Barclay, Candice J.; Jones, Elizabeth E.

    Journal article
    Lincoln University

    The susceptibility of four common grapevine rootstocks (101-14, Schwarzmann, 5C and Riparia Gloire) to Cylindrocladiella parva (black foot disease) infection was assessed in a pot experiment. The roots of 4-month-old callused rooted cuttings were wounded in situ and inoculated with 50 ml C. parva conidial suspension (106/ml) or sterile water (controls). After 6 months of growth, shoot dry weight was significantly higher for control plants (24.2 g) than for those inoculated with C. parva (16.5 g), but did not differ between rootstock varieties. Root dry weight was not significantly affected by C. parva inoculation, but root dry weight of 101-14 was significantly higher than other rootstocks. Incidence and severity of trunk infection were significantly affected by rootstock variety, being lowest in rootstock 101-14 plants than other rootstocks. None of the rootstocks tested was resistant to this pathogen.

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  • Revisiting utopia: how a legacy of idealistic plans resonates with Christchurch’s rebuild

    Bowring, Jacqueline

    Journal article
    Lincoln University

    Imagined landscapes find their form in utopian dreaming. As ideal places, utopias are set up according to the ideals of their designers. Inevitably, utopias become compromised when they move from the imaginary into the actual. Opportunities to create utopias rely largely on a blank slate, a landscape unimpeded by the inconveniences of existing occupation – or even topography. Christchurch has seen two utopian moments. The first was at the time of European settlement in the mid-nineteenth century, when imported ideals provided a model for a new city. The earthquakes of 2010 and 2011 provided a second point at which utopian dreaming spurred visions for the city. Christchurch’s earthquakes have provided a unique opportunity for a city to re-imagine itself. Yet, as is the fate for all imaginary places, reality got in the way.

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  • The incidence of goitre in newborn lambs from ewes fed fodder radish, rape or Italian ryegrass with or without iodine supplementation

    Judson, H. G.; Barrell, Graham K.

    Conference Contribution - Published
    Lincoln University

    Brassicas are an important forage species on many New Zealand sheep farms. However, glucosinolates present in some brassicas can cause iodine deficiency in lambs when pregnant ewes are fed such crops during gestation. To investigate the effect of differences in glucosinolate profile of fodder radish and a brassica on ewe thyroid function and incidence of goitre in lambs born to ewes grazing these crops during pregnancy, a 3 x 2 factorial study utilising three diets (Italian ryegrass, fodder radish, rape) and two rates of iodine (I) supplementation (with, without) was conducted. Thyroid hormone (T₃, T₄) response to a thyroid releasing factor (TRF) challenge in ewes and incidence of goitre in newborn lambs was determined. A mild goitre, based on thyroid weight:lamb weight ratio (g/kg) of >0.4, was recorded only in newborn lambs from ewes fed rape and the incidence was higher (75% vs 11%) in those without I supplementation. Pregnant ewes grazing radish or rape had the lowest T₃ and T₄ responses to TRF, except in the case of T₄ where there had been I supplementation. Differences in glucosinolate content and composition may explain the differing results for sheep fed radish or rape.

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  • An association between lifespan and variation in insulin-like growth factor I receptor in sheep

    Byun, Seung O.; Forrest, Rachel; Frampton, Christopher M.; Zhou, Huitong; Hickford, Jonathan G. H.

    Journal article
    Lincoln University

    Longevity in livestock is a valuable trait. When productive animals live longer, fewer replacement animals need to be raised. However, selection for longevity is not commonly the focus of breeding programs as direct selection for long-lived breeding stock is virtually impossible until late in the reproductive life of the animal. Additionally the underlying genetic factors or genes associated with longevity are either not known, or not well understood. In humans, there is evidence that IGF 1 receptor (IGF1R) is involved in longevity. Polymorphism in the IGF1R gene has been associated with longevity in a number of species. Recently, 3 alleles of ovine IGF1R were identified, but no analysis of the effect of IGF1R variation on sheep longevity has been reported. In this study, associations between ovine IGF1R variation, longevity and fertility were investigated. Polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) was used to type IGF1R variation in 1,716 New Zealand sheep belonging to 6 breeds and 36 fl ocks. Ovine IGF1R C was associated with age when adjusting for flock (present 5.5 ± 0.2 yr, absent 5.0 ± 0.1 yr, P = 0.02). A general linear mixed effects model suggested an association (P = 0.06) between age and genotype, when correcting for flock. Pairwise comparison (least significant difference) of specific genotypes revealed the difference to be between AA (5.0± 0.1 yr) and AC (5.6 ± 0.2 yr, P = 0.02). A weak negative Pearson correlation between fertility and longevity traits was observed (r = -0.25, P < 0.01). The finding of an association between variation in IGF1R and lifespan in sheep may be useful in prolonging the lifespan of sheep.

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  • Evaluation of a dairy agri-environmental programme for restoring woody green infrastructure

    McWilliam, Wendy J.; Fukuda, Y.; Moller, H.; Smith, D.

    Journal article
    Lincoln University

    Pastoral landscape woody vegetation provides ecosystem services, but potentially competes for space, light and nutrients that could provide additional farm production. A questionnaire determined the values and behaviours of New Zealand dairy farmers to evaluate voluntary agri-environmental programs for restoring woody vegetation. Findings indicate the area is increasing, while the composition and configuration of networks are changing and redistributing. Farms with little are losing more, and those with more are gaining. Farmers are planting new areas to increase their public ecosystem services, but may not provide these services through planting and management. Barriers include insufficient private woody vegetation ecosystem services, and low rates of growth of native plants. Government incentive programs are ineffective in overcoming barriers. Farmers may be motivated by stronger evidence of valued ecosystem services, information about their benefits and drawbacks, and how to support services through planting and management. However, a targeted environmental stewardship scheme is required to overcome barriers to planting, with government and the dairy industry working together to develop and maintain a landscape-scaled woody vegetation network on private and public land. Such networks would build sustainability and resilience into dairy farming, leading to an equitably sharing of benefits and costs of their public ecosystem services.

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  • An annotated checklist of the psyllids of New Zealand (Hemiptera: Psylloidea)

    Martoni, Francesco; Burckhardt, D.; Armstrong, Karen F.

    Journal article
    Lincoln University

    A checklist of extant species of Psylloidea in New Zealand is presented. The list is structured according to the latest taxonomic classification of families, subfamilies and genera. It includes 99 species, 71 of which are formally described and named, along with information on the host plants and the natural enemies as aspects that are either species-specific or assist in their recognition. An updated distribution of each species is given based on literature records and material held in the major New Zealand entomological collections and databases, including from very recent field surveys. A new record for New Zealand is Phellopsylla formicosa.

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  • Succession on New Zealand farms

    Old, Kevin; Nuthall, Peter L.

    Journal article
    Lincoln University

    There is a strong belief that few farmers think well ahead on matters of farm asset succession. Nor do they take action, despite most professionals recommending that plans should be developed early in the life of a farm after proper consultation with the likely stakeholders and professionals. This article reports on farmers’ current thinking about succession and progress in implementing succession plans.

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  • The socio-cultural impacts of tourism ; a review of literature, policy and research implications for New Zealand

    Simmons, David G.

    Report
    Lincoln University

    This paper has been commissioned by the New Zealand Tourist and Publicity Department. Its objectives are to present a discussion paper on the socio-cultural impacts of tourism and the requirements for their monitoring and planning. To achieve these objectives has required a wider review than simply summarising New Zealand and overseas studies and reports. Firstly, tourism is defined and its role in development discussed. Much of this first section focusses on tourism as a ‘product' and an industry. This discussion is supported by a number of sub-themes; why tourist's visit New Zealand, who 'owns' the tourism product, and how does this product evolve over time. The second major focus is on factors that contribute to socio-cultural impacts. A central theme here is that impact studies merely assist us in determining how well we are meeting our objectives. It is also argued that because the tourism product changes over time and is specific to different destination areas, we will need develop our own systems of planning and monitoring that suit our own unique position and culture. The studies reviewed are drawn together in Chapters 5 and 6 to create a monitoring and research framework for social impact assessment in New Zealand’s tourism development.

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  • Ecological restoration of dryland kānuka communities in an irrigated agricultural landscape

    Dollery, Rebecca

    Thesis
    Lincoln University

    The Canterbury Low Plains ecological district exists as a highly modified, productive landscape containing little of its original indigenous vegetation. The residual native plant communities comprise scattered fragments of dryland shrubland with varying degrees of legal protection. One such area, the Eyrewell Forest, comprised a matrix of small dryland kānuka (Kunzea serotina) communities subsumed within an exotic pine plantation (6,764 ha) and pastoral land, and was described as the largest kānuka shrubland stand on the Canterbury Plains. Since 2010, the plantation has been progressively removed for conversion to precision-irrigated dairy farming. Within this landscape matrix, the current project focused on the establishment of ecological restoration areas and corridors to re-construct, protect and enhance indigenous species and habitats. The community structure and ecology of plant assemblages and associated edaphic conditions within existing remnants were investigated to assist in design, implementation and management of 18 ecological restoration blocks encompassing approximately 150 ha. A particular focus was the importance of moss carpets within natural kānuka-dominant ecosystems. I investigated the responses of the habitat and its plant species to nutrient spillover from adjacent farmland and evaluated restoration techniques suitable for the task. Study of the remnant kānuka habitats revealed that the native vegetation is characterised by low-nutrient soils and the dry climate, supporting assemblages of plants with obvious xerophytic traits. Small-scale disturbance was found to be critical for regeneration of the single canopy species, kānuka, and an understory shrub, Pomaderris amoena. The dominant ground cover moss species, Hypnum cupressiforme, and two woody associates, Leptecophylla juniperina and Carmichaelia australis, regenerated in areas of low disturbance and high canopy cover. Germination trials had some difficulties; P. amoena seeds required heat treatment and naturally followed fires, but L. juniperina could not be germinated artificially. H. cupressiforme exerted significant influence over the functioning of the ecosystem with regards to hydrology, nutrient cycling and biotic interactions. Extremes of soil temperature and moisture were mediated by the moss carpet; soil nutrients, particularly mineral nitrogen, were reduced. The moss layer also had species-specific effects on flora but generally decreased germination and establishment of native species. Glasshouse trials showed that K. serotina, P. amoena and Kunzea robusta grew better with soil additions of nitrogen. C. australis and H. cupressiforme responded positively to lime additions, but L. juniperina showed no response. In the field, fertilisation had either negligible or detrimental effects on native species. Increased soil nutrients from organic amendments elicited exotic weed encroachment. Nutrient spillover from farmland was observed at least 30m into remnant kānuka ecosystems and was positively correlated with exotic weeds but negatively related to moss cover. Successful introduction of planted native species required protection from desiccation and competition from weeds. Tree guards successfully and cost-effectively sheltered young plants and moss. Weeds were best controlled by herbicide application and, moderately with moss and pine litter mulch. This research has contributed to the restoration of 150 ha of landscape restoration, generating practical applications for similar projects elsewhere. A major finding is the importance of integrating moss into dryland kānuka restoration projects.

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  • Development of a PCR-RFLP method to distinguish species within the Ilyonectria macrodidyma complex

    Outram, Megan; Jones, Elizabeth E.; Jaspers, Marlene V.; Ridgway, Hayley J.

    Journal article
    Lincoln University

    Species within the Ilyonectria macrodidyma complex are known plant pathogens and several are implicated as the causal agents of black foot disease of grapevines. The seven species within the complex can be identified by DNA sequencing of the histone H3 gene. In this study, a PCR-RFLP method to identify the species was developed. In silico digestion of the 500 bp histone H3 amplimer using MnlI showed that it could identify Ilyonectria sp. 1, Ilyonectria sp. 2, I. alcacerensis and I. macrodidyma. Subsequent in silico digestion with Hinf1 identified I. estremocensis, I. novozelandica and I. torresensis. The PCR-RFLP was validated using a collection of 40 I. macrodidyma complex isolates that had been recovered from symptomatic grapevines. Ilyonectria macrodidyma, I. novozelandica and I. torresensis were detected in that collection. Intraspecific polymorphism was only detected in I. torresensis. This method provides a rapid procedure for identifying individual species of the I. macrodidyma species complex.

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  • Method developments to extract proteins from oil palm chromoplast for proteomic analysis

    Lau, B. Y. C.; Deb-Choudhury, S.; Morton, James D.; Clerens, S.; Dyer, J. M.; Ramli, U. S.

    Journal article
    Lincoln University

    Proteins from the plant chromoplast are essential for many physiological processes such as fatty acid biosynthesis. Different protein extraction methods were tested to find the most robust method to obtain oil palm chromoplast proteins for mass spectrometry analysis. Initially, two different solvents were employed to reduce the fruit lipids. Then, two plant cell wall digestive enzymes were used to acquire the protoplasts to increase the protein extraction effectiveness. A two-stage centrifugation-based fractionation approach enhanced the number of identified proteins, particularly the fatty acid biosynthetic enzymes. The effectiveness of each extraction method was assessed using protein yields and 2DE gel profiles. The ideal method was successfully used to establish the 2DE chromoplast proteome maps of low and high oleic acid mesocarps of oil palm. Further nanoLC–MS/MS analysis of the extracted chromoplast proteins led to the identification of 162 proteins, including some of the main enzymes involved in the fatty acid biosynthesis. The established procedures would provide a solid foundation for further functional studies, including fatty acid biosynthetic expression profiling and evaluation of regulatory function.

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  • Landscape architecture student choice: Profession or provider?

    Barthelmeh, Michael R.; Karanja, Dennis

    Journal article
    Lincoln University

    Secondary school students face many choices about tertiary education. Some will have a career path in mind and choose to attend an institution that offers a relevant programme, while others will choose a programme offered by an institution that has been selected for other reasons. This paper investigates whether students enrolled in one of the three accredited landscape architecture programmes in New Zealand first chose their career rather than first selected an institution. It also reports on the factors that influenced these choices. Ninety-seven first-year landscape architecture students were invited to complete a self-administered questionnaire. Seventy-five per cent chose a career in landscape architecture first, rather than first selecting an institution. In choosing a career, extrinsic motivations were more important than family or institutional influences, but institutional influences were more important than family or extrinsic factors when selecting a provider. The main factors influencing choice have implications for the profession; they also have implications for institutions regarding programme distinctiveness. Many factors play a role in these choices, including selection of subjects at school. Survey respondents reported on their choices of subject at secondary school and the usefulness of those subjects to their landscape architecture programme. A particular combination of secondary school courses may be a useful signal for students to consider landscape architecture as a possible career path.

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  • Intensified agriculture favors evolved resistance to biological control

    Tomasetto, F.; Tylianakis, J. M.; Reale, M.; Wratten, Stephen D.; Goldson, Stephen

    Journal article
    Lincoln University

    Increased regulation of chemical pesticides and rapid evolution of pesticide resistance have increased calls for sustainable pest management. Biological control offers sustainable pest suppression, partly because evolution of resistance to predators and parasitoids is prevented by several factors (e.g., spatial or temporal refuges from attacks, reciprocal evolution by control agents, and contrasting selection pressures from other enemy species). However, evolution of resistance may become more probable as agricultural intensification reduces the availability of refuges and diversity of enemy species, or if control agents have genetic barriers to evolution. Here we use 21 y of field data from 196 sites across New Zealand to show that parasitism of a key pasture pest (Listronotus bonariensis; Argentine stem weevil) by an introduced parasitoid (Microctonus hyperodae) was initially nationally successful but then declined by 44% (leading to pasture damage of c. 160 million New Zealand dollars per annum). This decline was not attributable to parasitoid numbers released, elevation, or local climatic variables at sample locations. Rather, in all locations the decline began 7 y (14 host generations) following parasitoid introduction, despite releases being staggered across locations in different years. Finally, we demonstrate experimentally that declining parasitism rates occurred in ryegrass Lolium perenne, which is grown nationwide in high-intensity was significantly less than in adjacent plots of a less-common pasture grass (Lolium multiflorum), indicating that resistance to parasitism is host plant–dependent. We conclude that low plant and enemy biodiversity in intensive large-scale agriculture may facilitate the evolution of host resistance by pests and threaten the long-term viability of biological control.

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