Department of Pest Management and Conservation

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https://hdl.handle.net/10182/35

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.

Now showing 1 - 5 of 780

The ecology of giant buttercup in Golden Bay dairy pasture : A thesis submitted in fulfilment of the requirements for the Degree of Master of Applied Science at Lincoln University
(Lincoln University, 1993) Brown, W. J.
Giant buttercup (Ranunculis acris L.) is a major weed of Golden Bay dairy pastures but is controlled by sheep and deer. Phenoxy herbicide resistance has developed in on Golden Bay dairy farms as a result of regular application of MCPA and MCPB over 25 years. The objectives of this research were to study the seasonal growth of giant buttercup in Golden Bay dairy pasture and to survey farmer experience in attempting to control It. The effect of increasing soil fertility on giant buttercup was investigated. Some management strategies for controlling the weed are discussed. Seasonality observations showed that seedlings took four weeks from germination to grow their first leaf. Rhizome growth occurred in midsummer, immediately following the peak of flowering. Vegetative reproduction also occurred by axillary bud development. Other aspects of phenology were similar to previous ecological studies. Farmers with high giant buttercup populations used a wider range of control strategies than herbicides only. Herbicide usage did not correlate with giant buttercup populations. Pugging increased the amount of giant buttercup in pasture. Survey results suggested that some other factors were more limiting on milk production than giant buttercup populations. Three field experiments to study the influence of soil fertility on giant buttercup in dairy pasture were set up in September 1990. Four rates of lime (0, 1.0., 2.5 and 5.0t/ha},two rates of 30% potassic super phosphate (0 and 400kg/ha) and two rates of urea (0 and 100kg/ha) were applied on two sites with contrasting soil types on one dairy farm. On another soil type the 30% potassic super phosphate and urea rates were doubled. This site was a runoff usually grazed by calves or heifers and was less intensively farmed. Within dairy pasture giant buttercup crown leaves were typically taller than grass. During giant buttercup flowering this was by 4.3 cm on average. On the less frequently grazed runoff giant buttercup was usually 2.1cm shorter than grass but during flowering was taller by 3.3 cm. Giant buttercup cover was decreased up to 3.6% (p=0.036) with 30% potassic super phosphate application on the lower terrace only. Other fertilizers had no significant influence on giant buttercup cover. Grass and clover cover was increased on the lower terrace and the runoff with 30% potassic super phosphate application. The same treatment caused a decrease in the weed proportion on the runoff. Urea application increased grass cover and decreased clover cover on each site. Giant buttercup and grass height increased with both 30% potassic super phosphate and urea application on the upper terrace and on the runoff. On the lower terrace only grass height responded to urea. There was no height response to 30% potassic super phosphate on the lower terrace. Urea application resulted in smaller giant buttercup crown diameters on the upper terrace. A decrease of up to 58mm was observed (p=0.018). While Golden Bay dairy farmers have potential to control giant buttercup with herbicides if current recommendations are closely followed, integration of sheep onto dairy farms is likely to improve giant buttercup control. Soil fertility alteration is unlikely to assist giant buttercup control however the impact of increased available nitrogen requires further study.
Studies on fairy ring spot of carnations caused by Cladosporium echinulatum : A thesis submitted in partial fulfilment for the requirements for the degree of Master of Horticultural Science Lincoln University (University of Canterbury) New Zealand
(Lincoln University, 1990) Braithwaite, Mark
The causal fungus of fairy ring spot Cladosporium echinulatum (Berkeley) de Vries was isolated into pure culture. Three experiments investigated the growth and conidial production of the fungus on artificial media. At 15°C, V-8 juice agar (containing 10% or 20% V-8 juice) and malt extract agar were optimal for radial growth. The optimum temperature for growth was 15°C on malt extract agar but growth was slow, averaging 1.2mm increase in radius per day. Growth was less on synthetic media. Conidial production was highest on V-8 juice and potato carrot agars and in the light (12D:12L). Few conidia were produced in continuous darkness on these agars. Under greenhouse conditions, 20±5°C, leaves of carnation plants cultivar 'Mei Fu' were inoculated with conidia. The first symptoms were observed 9 days after inoculation (incubation period) ,and conidia began to develop on the leaf surface at 18 days (latent period). Once conidial production commenced ,numbers harvested daily rapidly increased to a mean of 25.1 conidia mm⁻² of infected leaf tissue. This remained relatively constant from day 4 to 16. Small numbers of conidia (0.5 mm⁻² of infected leaf) were still produced 38 days after initial production commenced. Light and scanning electron microscope (SEM) studies showed that the pathogen spread through leaves by intercellular hyphae, with no intracellular haustoria. A mat of mycelium developed in substomatal cavities and conidiophores emerged only through stomata openings. Fixing fresh samples in glutaraldehyde fumes, followed by air drying, gave best preservation of aerial conidiophores and conidia for the SEM studies. Trapping of conidia in a greenhouse showed that air-borne concentrations followed a circadian periodicity with maximum numbers of conidia occurring around midday. These high numbers of conidia were highly correlated with decreasing relative humidity and leaf surface wetness and increasing temperature. High air-borne concentrations of conidia were also associated with overhead watering and the corresponding crop disturbance and fluctuations in relative humidity. Eight experiments evaluated the efficacy of 17 fungicides against C echinulatum. These included in vitro studies, pot trials and commercial greenhouse trials. In vitro, chlorothalonil, maneb, imazalil, pyrifenox and triforine inhibited conidial germination at I00mg l⁻¹ and imazalil, prochloraz. pyrifenox, cyproconizole, flusilazol, hexaconazole, myclobutanil, propiconazole, terbuconazole and carbendazim inhibited radial growth at 1mg l⁻¹. Greenhouse pot trials assessed the protectant and eradicant properties of 13 fungicides. Each fungicide was applied either three days before or three days after inoculation with conidia. Chlorothalonil, maneb and mancozeb were observed to be effective protectants. The site-specific chemicals prochloraz. pyrifenox and CGA 169374 were effective as both protectants and eradicants. Commercial greenhouse trials showed that when disease pressure was high prochloraz, pyrifenox and CGA 169374 provided good disease control as compared to unsprayed plots.
Bacterial and protozoan diseases of insects: Entomology dissertation
(Lincoln College, University of Canterbury, 1969) Butcher, C.
The study of insect diseases is a very exacting one. The disease oust be adequately identified and documented. The causative agent must not be confused with secondary invaders of the dead insect or with naturally recurring symbionts .Also culture of the pathogen may be impossible, limiting the chance of detailed study - thus some early reports of insect diseases may just as well be invalid because of inadequate description or preservation of the causative agent. Recent techniques of continuous culture in microbiology and the setting up of micro-biological museums where continuous cultures are kept in the condition they were discovered , will doubtless help insect pathology . ln this project bacterial diseases will be dealt with first followed by protozoan diseases .
Ecological and physiological studies of Tradescantia Fluminensis Vell. : A thesis submitted in partial fulfilment of the requirements for the degree Master of Applied Science at Lincoln University
(Lincoln University, 1991) Maule, H. G.
Tradescantia fluminensis Vell. is a herbaceous perennial, native to tropical South America which has become established in many native forest remnants in the North Island and northern South Island of New Zealand. Tradescantia has been implicated in suppressing regeneration of these remnants. Laboratory and field studies of growth, nitrogen nutrition and acclimation of Tradescantia to different irradiance levels were conducted with the objective of determining reasons for the success of Tradescantia in New Zealand forest remnants. The field site was a native forest remnant located in Akaroa, Canterbury, New Zealand (National grid reference NZMS 260 N36, Akaroa 076113). Over a two year period in the field, Tradescantia displayed a very seasonal growth pattern, which correlated positively with temperature. Length increase of individual plants was estimated at around 0.65 m yr⁻¹. However, plant length and dry weight (d.wt) changed little over the two year period. Nitrate (NO⁻³) content was measured in all tissues during the first year of the study. Stem tissue always contained over 0.3 mmol NO⁻³ g⁻¹ d.wt. In the glasshouse, plant d.wt and shoot to root ratio increased with increased NO⁻³ 0.1 to 5 mol m⁻³. At low concentrations (0.1-1 mol m⁻³) ammonium (NH4⁺) gave similar growth to NO⁻³ but at 5 mol m⁻³, NH4⁺ toxicity symptoms developed. Growth rate at high NO⁻³ was almost an order of magnitude greater than that found in the field. Nitrate content of all tissues increased with increased applied NOj concentration. Nitrate reductase activity (NRA) of all tissues increased with increased applied NOj from 0.1 to 0.5 mol m⁻³ then changed little with further increases in applied NO⁻³ thereafter: activity was greater in leaves than in stem or root at all concentrations of applied NO⁻³. The shoot was the main site of NO⁻³ accumulation (>95% total plant NO⁻³) and NRA (around 95% total plant NRA). Tradescantia utilised accumulated NO⁻³ when external NO⁻³ supply was reduced or withdrawn. In the glasshouse, plant d.wt at low (0.5 mol m⁻³) and high (5 mol m⁻³) NO⁻³ supply increased with increased irradiance 1 to 26% (open ground photosynthetically active radiation= 100% relative irradiance) then changed little with increased irradiance thereafter. Values were greater at high than at low NO⁻³ at all but the lowest irradiance level. Regardless of treatment, 87% or more of plant d. wt was partitioned fairly evenly between leaves and stem. The major part of irradiance effects on leaves occurred over the irradiance range 1 to 26%. At both low and high NO⁻³ specific leaf area (SLA), chlorophyll per unit d.wt and carotenoids per unit d.wt decreased with increased irradiance over this range, while protein per unit d. wt increased with increased irradiance 1 to 3%, then decreased with increased irradiance 3 to 26%. At low NO⁻³, chlorophyll and carotenoids per unit area decreased with increased irradiance 3 to 26%, at high NO⁻³, chlorophyll per unit area did not change with irradiance while carotenoids per unit area increased. Regardless of NO⁻³ supply, protein per unit area increased with increased irradiance 1 to 26%. For all measurements, values were greater at high than at low NOj at all but the two lowest irradiance levels. At both low and high N0⁻³ the chlorophyll to carotenoids and chlorophyll to protein ratios decreased with increased irradiance 1 to 26%. The chlorophyll a to chlorophyll b ratio was not affected by either irradiance or N0⁻³. On high N0⁻³ supply outdoors, the chlorophyll a to chlorophyll b ratio increased with increased irradiance. Changes in SLA, chlorophyll (a+b), carotenoid and protein content associated with increased distance into a forest remnant were similar to those obtained with decreased irradiance in both experiments. Chlorophyll a to chlorophyll b ratio decreased with increased distance into the remnant. It is concluded that; a) growth is highly influenced by seasonal temperature, b) in an established sward, growth at the apex is balanced by death at the base, c) Tradescantia shows features of N nutrition characteristic of ruderal, nitrophilous, and tropical species, d) Tradescantia is capable of acclimation to and growth at a wide range of irradiance levels and e) low irradiance appears to be the major factor limiting further colonisation of forest remnants. These data are discussed in relation to a possible strategy employed by Tradescantia in invasion of native forest remnants.
Understanding the life cycle of the floral microbiota of Leptospermum scoparium (mānuka) : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Larrouy, Justine
Leptospermum scoparium is a shrub native to New Zealand and holds high cultural value (taonga = a treasure) and economic value due to the antimicrobial mānuka honeys produced from its nectar. Previous studies demonstrated a high frequency of association between microorganisms and the leaves, stems and roots of L. scoparium, with some modifying the secondary metabolite profile of L. scoparium leaves and improving growth. Flowers are an important niche for microorganisms; however, no research has focused on the L. scoparium anthosphere (flower), despite its potential impact on the honey industry. The aim of this research was 1) to characterize the endophytic and epiphytic microbial communities associated with L. scoparium flowers, 2) to characterize the effect of floral development on the anthosphere community of L. scoparium, 3) to determine the origin of the microbial communities associated with L. scoparium flowers, and 4) to determine the effects of soil on the bacterial communities associated with L. scoparium flowers. To answer these objectives, bacterial and fungal communities were characterized using 16S rRNA and ITS1-based community profiling (or cultivation independent approach) by high throughput sequencing. Host contamination (plastid and mitochondrial sequences) in 16S rRNA amplicon sequencing from plant samples impedes plant microbiota studies, thus I first optimised the 16S-sequencing method for L. scoparium bacterial microbiota studies (overall increase of bacterial sequences by 30%) based on modifications to the published Cas9-16S seq method. I then characterized for the first time which bacteria and fungi that live in (endophytic community) and on (epiphytic community) L. scoparium flowers. The results showed that nectar-consuming yeasts from Aureobasidium and Vishniacozyma genera, functionally diverse filamentous fungi from the Cladosporium genus, and bacteria from Candidatus Phytoplasma, Pseudomonas and Pantoea dominated the L. scoparium anthosphere. The L. scoparium epiphytic community was richer (5.6 times and 2.5 times more bacterial and fungal OTUs) and differed in composition relative to the endophytic community (p < 0.001), demonstrating filtering by the plant. This study demonstrated that a wide diversity of microbial taxa inhabit the L. scoparium anthosphere. As flower morphology and biology change rapidly over time, dynamic niches for microorganisms are formed and lost. Floral physiology at each life stage can therefore influence arrival, persistence, and loss of microbial species; however, this remains poorly understood despite its potential consequences for host reproductive success. Thus, I characterized the effect of transition through five floral stages on the flower-inhabiting bacterial and fungal communities, from immature bud to spent flower, and subsequent allocation to seed. The results showed a core microbiota (representing >80% of all fungal reads and between 47.5% and 94.0% of all bacterial reads at each floral stage) persisted across this dynamic niche despite high microbial turnover, as observed in shifts in community composition (p = 0.001) and diversity (increase in alpha diversity between closed and open floral stages, p<0.001) as flowers matured and senesced. The results demonstrated that floral stages are strong drivers of the L. scoparium anthosphere community assembly and dynamics. One of the challenges for research seeking to understand the origin and dynamics of floral microbial communities is that every year floral microbiota must begin anew, and, unlike other vegetative organs (roots, stems, and leaves), develop and exist for a limited time. In this study, I collected flowers from L. scoparium plants over two consecutive flowering seasons to understand the effect of seasonality on shaping the microbial community. I also characterized the microbiota within different niches of L. scoparium; flowers, bagged flowers (to exclude animal visitation), leaves, underlying flower stems and lateral roots, and surrounding the plants; soil and bee surfaces to understand the origin of flower-inhabiting microorganisms. The results showed that the L. scoparium anthosphere community was recruited from more than one reservoir. Local reservoirs (leaves, stems) were an important source of microorganisms for the L. scoparium anthosphere (41% of the bacterial and 81% of the fungal community potentially originated from leaves), however pollinators were also important for bacterial community assembly (>25% bacterial community potentially originated from bee visitations). The selection or specialisation of microorganisms was demonstrated across flowering season with a few highly prevalent and abundant taxa (representing >90% of the reads for fungal and bacterial communities in both years). However, most of the taxa retrieved were not prevalent in flower samples indicating stochasticity in the anthosphere assembly process that may depend on environmental conditions, vectors and the microbial community surrounding the flower at the time. Finally, as the rhizosphere is an interface for plant microbial acquisition, soil is an important factor for microbial colonisation of plants. To date there has been little research conducted on the contribution of soil bacteria to the anthosphere bacterial community. Thus, seedlings of L. scoparium were planted in pasteurized potting mix and in soils collected from three contrasting sites. Once the first flowers appeared (~1.5 years), flowers and soil were collected for 16S rRNA gene community profiling. I found that soil played a relatively small role in bacterial community composition of L. scoparium flower, as the anthosphere bacterial community for plants grown in only one soil, ‘home soil’, was different compared to the anthosphere bacterial community for the plants grown in the other soils or pasteurize potting mix (p <0.05). In this research, new understanding of the spatial and temporal floral microbiota of L. scoparium was produced, demonstrating its likely origin and recruitment pathways and the impacts of floral development, organ/tissue filtering and soil on community assembly and dynamics. Finally, this research demonstrated that interaction between microorganisms is likely to play an important role in shaping L. scoparium anthosphere. This study builds fundamental knowledge in microbial ecology of healthy flowers as well as producing a foundation for further research on enhancing the production of mānuka honey by manipulating floral microorganisms.

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