Department of Pest Management and Conservation

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The Department of Pest Management and Conservation carries out research and teaching in the following specialist areas: Animal behavior; Conservation and biodiversity; Ecological restoration; Evolutionary biology; Fire ecology; Molecular ecology; Plant microbiology; Plant pathology; Remediation of degraded and contaminated land; Soil ecology; Sustainable agriculture and ecosystem services; Wildlife and pest management.

Recent Submissions

Now showing 1 - 5 of 806
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    Evaluating the densities and distribution of root-lesion nematodes (Pratylenchus spp.) in wheat grown in Canterbury, New Zealand
    (New Zealand Plant Protection Society (Inc.), 2023-05-18) Thiellier, MJ; Kularathna, Manjula
    Species of root-lesion nematode (Pratylenchus spp.) are associated with significant reductions in wheat yield in wheat-growing regions around the world. Of these, Pratylenchus thornei and P. neglectus are known to cause the highest damage to the Australasian wheat industry. New Zealand is known to produce high wheat yields on a per-hectare basis yet little research has been conducted to date to determine the effects of Pratylenchus spp. on the production of wheat in New Zealand. Therefore, as the first step towards filling this knowledge gap, the current research focused on conducting surveys to determine the population densities and distribution of Pratylenchus spp. in wheat-growing regions in Canterbury, South Island, New Zealand. Surveys were conducted at ten selected sites that were geographically distinct from each other. At six of the ten sites, lesion nematode populations were reported to be above the recorded Australian threshold of 2000 nematodes per kg of soil. In Australia, it’s been recorded that around 50% yield reductions can occur in intolerant wheat varieties when population densities reaches this number. Differences in population density within each location was also observed indicating the uneven distribution of lesion nematodes within a field. Morphological measurements of the nematodes collected from multiple sites during this study confirmed the presence of P. thornei and P. neglectus in Canterbury wheat-producing areas indicating a potential threat to the New Zealand wheat industry by root-lesion nematodes. Further studies need to be conducted to fully understand the situation and to develop management strategies to mitigate threats from nematodes.
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    Soil carbon, erosion, and the stormflow mobilisation of sediment and nutrients in a high-country landscape : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
    (Lincoln University, 2023) Provost, Shyam Michael
    This study was carried out at Mt. Grand Station, a high-country pastoral farm in the South Island of New Zealand. The landscape (400 - 1300 m altitude) supports a gradient and mosaic of native and endemic woody shrub and tussock grassland vegetation amongst more productive exotic pasture, the latter established through aerial seed top-dressing and fertilisation. In recent years several areas of the farm at higher altitudes have been converted to conservation management following Tenure Review, placing additional pressure on the remaining farmland to maximise productivity, a situation similarly faced by many other high-country farms. However, further intensification of pasture grassland would compromise existing less productive native vegetation. This research project investigated soil conservation and loss, and freshwater quality, aiming to advance existing knowledge relating to environmental sustainability of the high-country. Topsoil carbon stocks were quantified beneath various vegetation communities at different altitudes of the station to gain a better understanding of soil carbon and its dynamics. Two watershed catchments were targeted for high-frequency sampling during rainfall events, to investigate the likely significance of water flow on the mobilisation of sediment and nutrients, and to help improve the accuracy of existing run-off estimates. In addition, soil erosion was estimated from differences in residual soil 137Cs activity, which was generated from historic Pacific nuclear testing, between two of the dominant types of vegetation cover. The results revealed the potential for native vegetation to enhance soil carbon sequestration. At low - middle altitudes (450 - 850 m) of the farm, topsoil beneath a woody shrub (kānuka) vegetation cover had significantly higher carbon concentrations and carbon stocks than areas of adjacent pasture. At higher elevations (>1000 m) topsoil beneath dominant snow tussocks had significantly higher carbon, nitrogen and phosphorus concentrations, with higher carbon stocks than adjacent inter-tussock spaces. The total loads of suspended solids, nitrogen and phosphorus exported to catchment waterways were significantly larger during high-flow events in comparison to baseflow conditions, and large proportions of the high-flow loads were mobilised on the rising hydrograph following high rainfall. These findings draw attention to the significance of taking account of the early stages of rainfall events to improve accuracy when quantifying high-country catchment loads. Data for 137Cs were variable but these provisional results indicate that soil beneath kānuka is likely to have undergone lower rates of erosion over the previous 65 years in comparison to areas of adjacent pasture. The combined findings of the three parts of the experimental work in this study are interpreted as being indicative of the present and future potential for South Island high-country farming environments to make a significant contribution towards climate change mitigation through vegetation management, resultant soil building and prevention of soil erosion. It is argued that closer attention to ecological restoration is likely to have mutual benefits for conservation, the farming system and the environment. Maintenance and better-informed management of the mosaic of native and exotic vegetation can play a more important role in longer-term sustainability of this high-country land management system than is currently appreciated.
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    Copper contamination of fruit orchards soils: Biotic Impacts : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
    (Lincoln University, 2024) Jeon, Dasom
    Extensive use of fungicide copper (Cu) has a more recent history in New Zealand than in many other parts of the world where long-lasting Cu accumulation in soil has become a major environmental issue. However, Cu is extensively applied in New Zealand orchards, including organic orchards, with some awareness that the consequences of its current and future accumulation on soil health are relatively unknown and under-explored. This doctoral study aimed to investigate the impact on soil functional processes and plants of soil copper contamination associated with cherry, apple and kiwifruit orchards, vineyards and hops. The research encompassed experimental work on soil respiration, plant growth, earthworms, soil microbial activity, root growth and plant cell culture through a combination of fieldwork, glasshouse and laboratory studies. The central hypothesis of this study was that accumulation and persistence of Cu in orchard soils are likely to adversely affect critical aspects of soil biology and functionality. Following a detailed survey of accumulation and spatial variability of soil Cu across different fruit orchards up to 73 years old, practical investigations involved soil respirometry, analysis of microbial carbon (C) and nitrogen (N), and rhizobox and pot plant growth assays, as much as possible using in-situ field measurements or soils collected from orchards and transferred to the glasshouse and laboratory. In an earthworm behavioural and Cu-uptake study, a native anecic species was exposed to soils from the same orchard with differing histories of fungicide use. Three hop varieties (Cascade, Nelson Sauvin and Riwaka) were used for plant growth trials on the same soils. Plant stress responses were investigated using callus incubation trials on cell lines isolated from three apple cultivars (Braeburn, Fuji, and Cripps Pink) grown on a Cu-spiked growth medium. All practical work was carried out from 2020 to 2023. The results showed that soil Cu concentrations in orchards frequently and substantially exceeded most published threshold limits. Whilst soil Cu concentrations could largely be explained by modelling the age of the orchards, fruit type and soil organic matter (SOM) also had a large role in Cu retention. When SOM and existing Cu concentrations were amended in four soils from different blocks of the same cherry orchard, the ecotoxicological impact differed, and it was found that SOM could be a more powerful determinant than Cu of the biotic responses. Earthworm survivorship and growth in these soils were significantly determined by both SOM and Cu; earthworms exhibited a preference for soils with concentrations of Cu elevated substantially above background (to 160 mg kg-1), where SOM content was also high. A variable impact of Cu contamination on soil microbial activity was recorded across soils with elevated Cu concentrations (from 195 to 405 mg kg-1). Only a weak correlation was found between soil total Cu concentration and soil respiration when data for all orchards were combined, but the impact of Cu was more evident when each type of fruit orchard was evaluated separately. Microbial biomass carbon (MBC) and nitrogen (MBN) analyses similarly provided only a weak or negligible correlation with soil Cu, but artificially spiked soils provided a more consistent response to elevated Cu. Confounding factors appeared to relate to vegetation cover within and between rows and the amount of cultivation of the soils used to manage weeds (and bronze beetle in apples). The influence of management variables requires a more detailed study. Root growth in hop varieties was negatively affected at Cu concentrations exceeding 263 mg kg-1, whilst best growth was observed at 160 mg kg-1 in conjunction with abundant SOM. In callus culture assays, Cu negatively impacted the growth of Braeburn and Fuji apple varieties at concentrations exceeding 15 mg kg-1, while Cripps Pink had higher Cu tolerance. The value of using biological and ecological indices to assess the impacts of agricultural chemicals and contaminated soils is discussed. The findings have identified detrimental biotic impacts of soil Cu concentrations that already exist in orchards, which are probably reflected in a negative influence on soil health. Transfer rates of Cu to fruits through uptake from soil or from foliar absorption are negligible, but stress responses in plants and soil fauna and impacts on soil biology and ecology have been detected. Currently, the deleterious impact of elevated Cu is largely mitigated by SOM content in combination with the avoidance of low pH in orchard soils. Whilst this implies there is a potential avenue for amelioration of toxicity and maintenance or restoration of soil health, residual fungicide Cu will not significantly dissipate and is likely to continue to accumulate. Sustainable soil health management in New Zealand's orchards is not viable with longer-term continued usage of Cu fungicides.
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    Investigation of the microbiome structure and function in grapevines escaping trunk diseases : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
    (Lincoln University, 2023) Adejoro, Damola
    Grapevine trunk diseases (GTD) represent a substantial challenge to viticulture in New Zealand and other winegrowing regions worldwide. With no approved fungicides for their eradication, alternative methods, such as biological control, are of significant interest. Key international studies have identified plants, called disease escape plants, that remain healthy under a high disease pressure, and this trait has been linked to microbiome function. In some New Zealand vineyards, such disease escape vines have been observed in backgrounds of heavy GTD pressure. This study aimed to investigate a microbiome approach to GTD management by surveying New Zealand vineyards for the occurrence of GTD escape vines and characterising the trunk microbiome of such vines. Based on preliminary assessments of nine vineyards across Hawke's Bay and Canterbury, New Zealand, a detailed visual survey was conducted in four vineyards, two each in Hawke's Bay and Canterbury. Candidate GTD escape vines were identified based on the absence of GTD symptoms, chlorophyll content of leaves, and high GTD pressure in the vineyard block. Woody trunk tissue samples were collected from these vines and the diseased vines nearby. The fungal and bacterial communities in the samples were characterised using a combination of DNA metabarcoding of the ribosomal internal transcribed spacer 1 (ITS1) and 16S ribosomal RNA gene and microbial isolations. The results showed that the status of the vine as either GTD escape or diseased was a strong determinant of the structure of the bacterial and fungal microbiomes of the grapevine trunk. For bacteria, the GTD escape vines consistently harboured Pseudomonas and Hymenobacter in higher relative abundance. Aureobasidium, Seimatosporium, Cladosporium, and Rhodotorula were fungal genera differentially associated with GTD escape vines. On the other hand, the GTD pathogen, Eutypa lata, was differentially associated with diseased vines. Bacterial and fungal isolates matching the key taxa identified by DNA metabarcoding from GTD escape vines were retrieved and tested for inclusion in microbial consortia. Additional selection criteria for inclusion were the microorganism's functional properties, such as not being a known plant pathogen, not causing lesions on grapevine shoots, and exhibiting desirable inhibitory activities against E. lata and Neofusicoccum luteum in dual culture plate assays. Using these criteria, consortium members Aureobasidium pullulans, Seimatosporium vitis, and seven Pseudomonas isolates were selected. Combined and separate fungal and bacterial consortia were tested in plant assays against the GTD pathogens E. lata and N. luteum. Over 3 months, the bacteria successfully established and persisted within the grapevines, significantly altering the grapevines' microbiome structure. Treatment with combined bacterial and fungal consortia resulted in significantly shorter lesions (71% reduction, p = 0.002) than the pathogen controls. The relative abundance of E. lata was reduced by 85% in the presence of the bacteria-only consortium. This research enhanced knowledge of the grapevine trunk microbiome structure within the context of the GTD escape phenotype. In addition, it expanded the understanding of grapevine microbiome manipulation by developing and delivering microbial consortia into grapevines, which resulted in changes in the grapevine microbiome structure. These results highlight the potential of using selected microbial consortia as a promising strategy for controlling GTD pathogens in planta. Given the perennial nature of grapevines and the extended development periods associated with GTD, future research could investigate the potential long-term impact of grapevine microbiome manipulation on the protection of grapevines against GTD pathogens.
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    Adaptation and survival of marine-associated spiders (Araneae)
    (Annual Reviews Inc., 2024-01) Leggett, MA; Vink, Cornelis; Nelson, XJ
    Aquatic environments are an unusual habitat for most arthropods. Nevertheless, many arthropod species that were once terrestrial dwelling have transitioned back to marine and freshwater environments, either as semi-aquatic or, more rarely, as fully aquatic inhabitants. Transition to water from land is exceptional, and without respiratory modifications to allow for extended submergence and the associated hypoxic conditions, survival is limited. In this article, we review marine-associated species that have made this rare transition in a generally terrestrial group, spiders. We include several freshwater spider species for comparative purposes. Marine-associated spiders comprise less than 0.3% of spider species worldwide but are found in over 14% of all spider families. As we discuss, these spiders live in environments that, with tidal action, hydraulic forces, and saltwater, are more extreme than freshwater habitats, often requiring physiological and behavioral adaptations to survive. Spiders employ many methods to survive inundation from encroaching tides, such as air bubble respiration, airtight nests, hypoxic comas, and fleeing incoming tides. While airway protection is the primary survival strategy, further survival adaptations include saltwater-induced osmotic regulation, dietary composition, predator avoidance, reproduction, locomotory responses, and adaptation to extreme temperatures and hydrostatic pressures that challenge existence in marine environments.