Search

Coconut production in the Pacific Islands is threatened by coconut rhinoceros beetle (CRB). Distinctive feeding damage caused by adults is often the first indicator of CRB activity in a new location. Multiple approaches to damage assessment have been used, reflecting observers' experience. The lack of standardisation makes it difficult to compare CRB impacts on coconut palms over time. We examine damage assessment from three perspectives: participants, power and purpose. Participants applied binary, 3-point and 5-point damage scales consecutively to photographs of damaged palms. Participant responses were more accurate using the binary scale compared with the 5-point scale. Experience with CRB improved accuracy, but this did not wholly compensate for the effect of scale complexity. Calculations of statistical power determined minimum sample sizes to detect a 20% change in palm damage was 50 palms for the binary scale, 150 palms for the 3-point scale and > 200 palms for the 5-point scale, when the change in damage was spread across damage categories. More complex damage scales did not increase the likelihood of detecting significant changes in palm damage. With real-world examples, including detecting new outbreaks and managing established populations, recommendations were developed to standardise damage assessment for CRB on coconut palms. [ABSTRACT FROM AUTHOR]

Segregation into lustrous and wild-type birth coats suggested both dominant and recessive inheritance patterns associated with birth coat and subsequently with low wool fibre curvature at lamb and yearling shearing. The hypothesis that these phenotypes also differ in the proportion of medullated fibres (%) was tested here. Progeny expressing dominant segregation of lustre at birth showed significant differences in medullation of lambs wool (P < 0.001), where 42.3% (SEM ± 6.5%) of fibres were medullated in the lustrous phenotype, and 4.8% (± 1.0%) in the wild-type. Medullation at yearling shearing had declined to 19.7% (± 5.3%) and 1.8% (± 0.3%) respectively but the significant difference prevailed (P < 0.001). Progeny expressing recessive segregation of lustre also exhibited more medullation as lambs (54.6% ± 6.0%) with only 9.5% (± 2.6%) in the wild-type (P < 0.001). Again, medullation declined in yearlings but the difference (P < 0.001) between phenotypes remained (22.6 ± 8.2 vs. 4.0 ± 1.7%). For both inheritance patterns medullation increased as fibre diameter increased in lambs wool (P < 0.001), but across the range of fibre diameter observed, more fibres were medullated in those lustrous at birth (P = 0.001). [ABSTRACT FROM AUTHOR]

This paper discusses demographic and study-related factors that contribute to completion of degrees in one university in New Zealand. Although much can be learned from nationwide and cross-institutional studies, it is important that each institution comes to an understanding of its own particular student population and the factors that impact on retention and completion in its own context. Institutions have different student populations and different contextual factors that impact on completion rates. Understanding institutional data will enable strategies and interventions that are relevant to its particular context. In this initial project we sought to replicate, as closely as possible, a nationwide study with a similar focus. Using a similar statistical approach enabled us to compare the results. The main questions the authors sought to answer, therefore, were: (1) do completion rates within one institution differ between years; (2) what are the differences in completion rates and factors between the overall national data and the single institution data, and what can be learned from that for possible interventions? The results suggest that although there are similarities between the two studies, there were significant differences as well. These differences could be used to inform institutional interventions that would enhance completion rates.

Context: Biological nitrogen (N) fixation through the rhizobia–legume symbiosis is a sustainable and cost-effective source of N for agriculture. In New Zealand (NZ), white clover (Trifolium repens) is a key component of pastures and rhizobial inoculation of clover is widely used. The current commercial inoculant for white clover, TA1, was isolated in Australia in the 1950s and may not be the best partner for modern white clover cultivars. Aims: To identify Rhizobium leguminosarum bv. trifolii (Rlt) isolates suitable for use in NZ pastures. Methods: The symbiotic potential of >230 isolates collected from throughout NZ was evaluated in plant bioassays. Selected isolates were further evaluated in pot and field trials. Key results: Approximately 40% of NZ isolates supported better clover growth than TA1 under N-limited conditions in vitro. Of 24 Rlt isolates evaluated in a glasshouse trial, five produced significantly higher clover biomass than TA1. Three (S11N9, S20N7, S4N6) of nine isolates evaluated in two field trials in 2018–2019 significantly increased clover growth (12–38%) compared with paired uninoculated clover at several harvests, whereas inoculation with TA1 did not improve yield. In a third trial in 2020, S11N9 and S20N7 increased clover growth compared with the uninoculated control at two of three harvests; S4N6 performed better than TA1 at one harvest. When tested with four white clover cultivars, five Rlt isolates had higher symbiotic potential than TA1. Conclusions: Inoculating white clover would be beneficial if improved inoculant isolates were available. Implications: We recommend some NZ Rlt isolates could be developed into commercial inoculants to improve white clover performance in NZ. Enhancing biological nitrogen fixation through the rhizobia–legume symbiosis is urgent, as concerns over environmental impacts of intensive agriculture increase. Despite the importance of legumes in New Zealand's pastures, there has been little emphasis placed on rhizobium, and modern white clover cultivars still rely on a commercial inoculant TA1 isolated from 1950s. A few rhizobial isolates identified in this study performed better than TA1 and could be developed into commercial inoculants to improve white clover performance in New Zealand. [ABSTRACT FROM AUTHOR]

Soil associated with sea freight (shipping containers, flat racks and used machinery) arriving at New Zealand seaports was sampled for bacteria, fungi, nematodes, macro-invertebrates and plant seeds. Pseudomonads were selectively isolated, as several significant plant pathogens fall within this bacterial group. The mean and median sample weight collected from sea freight was found to be 417.3 and 152.7 g, respectively, with most recovered soil (73%) collected from the underside of shipping containers and flat rack containers. Likewise, for used machinery, most recovered soil (75%) was found under the machinery. Flat rack containers had significantly higher soil contamination compared to shipping containers and used machinery, but generally the counts and incidence of taxa were significantly lower compared to these other freight types. Viable bacteria, fungi, nematodes, seeds and arthropods were associated with the soil, with both counts g-1 and prevalence in samples varying with taxa, freight type, and location on the freight. Various regulated biosecurity organisms were recovered from the samples, including Aphelenchoides besseyi (rice white tip nematode), and seeds from genera such as Brachiaria, Cortaderia, Digitaria, Eragrostis and Sonchus. There were also live arthropod taxa that were not recorded as being present in New Zealand. No known plant pathogenic pseudomonads were identified through sequencing of the 16S ribosomal RNA gene. Shipping containers were found to be an important introduction pathway for exotic species, and therefore require careful monitoring and management. Comparisons of the incidence and mean number of organisms associated with soil on sea freight compared to a previous study with soil on footwear, generally showed that incidence and counts of many taxa were lower on sea freight, indicating that biosecurity risk can vary with pathway. However, prioritising one soil pathway over another according to the risks they present, and differentially allocating resources is problematic because the relative risk is dynamic, dictated by factors such as new pests or diseases entering the respective pathways. [ABSTRACT FROM AUTHOR]

New Zealand's economically vital exotic pastures are unique in their low complexity making them highly susceptible to invasive pest species such as the Argentine stem weevil Listronotus bonariensis. This field-based contribution further examined the ecology of the adult weevil and its parasitoid control agent Microctonus hyperodae. This included factors that affect field sampling accuracy, interpretation of population density and parasitism estimates. Compared to adult population estimates measured via turf flotation, suction sampling (G-vac) showed c.30% under-estimation of population densities while parasitism rates were over-estimated by c.26%. The bionomic implications of the sampling biases are discussed as they relate to the recently observed sharp declines in L. bonariensis parasitism. The weevil's field parasitism rates showed no relationship to population density again confirming the parasitoid's very high host searching efficiency. This study also coincided with meteorological conditions (>30°C) that resulted in a very large L. bonariensis 'swarming' event. The mass emigration from the experimental plots left only a low residual population of parasitised weevils that typically do not fly. Therefore, measured L. bonariensis populations and their M. hyperodae parasitism levels cannot always be presumed to be solely the result of population dynamics in situ. [ABSTRACT FROM AUTHOR]

Ripgut brome (Bromus diandrus) is a significant weed in arable systems with cereals being negatively impacted through yield reduction and contamination of harvested grain. There are limited herbicide options for its control, and reduction of the weed seed bank is a key part of its management. Ripgut brome seeds were incubated in three soils known to harbour a range of plant pathogens, and a range of fungi were subsequently isolated from ungerminated seeds. The most prevalent putative fungal pathogens isolated were Fusarium spp. and Marasmius sp. Selected isolates were cultured on artificial media and tested for their ability to inhibit germination of ripgut brome seeds in a series of in vitro assays, with many isolates completely inhibiting germination. When isolates were tested for their activity against non-target arable species in plant assays, three of five Fusarium spp. isolates significantly inhibited germination of oats and barley while a Marasmius sp. isolate had no effect on germination of these species. Further plant assays using four Marasmius sp. isolates against a wider range of plant species (oats, barley, ryegrass, brome, cocksfoot, and prairie grass) indicated some variability between Marasmius sp. isolates, with two isolates slightly inhibiting germination of some plant species, while two isolates (W14, W17) had no adverse effects. Sequencing of the ITS region of the Marasmius sp. isolates indicated that they were closely related but distinct from M. graminum, which is known to have some phytopathogenic activity and M. oreades which has not yet been reported as a plant pathogen. Further investigation of the Marasmius isolates as potential biocontrol agents for ripgut brome seed is warranted. [ABSTRACT FROM AUTHOR]

Curvature in mammalian fibers, such as wool and human hair, is an important feature of the functional trait of coat structure—it affects mechanical resilience and thermo‐insulation. However, to examine the relationship between fiber curvature, ultrastructure and protein composition fiber diameter variability has to be minimal. To achieve this we utilised the progeny of straight‐wool domestic sheep mutant rams (crimp mutants) and wild‐type ewes. Proteomic and structural results of the resulting mutant/wild‐type twin pairs confirmed that straight crimp mutant wool had a normal cuticle and the same cortical protein and ultrastructural building blocks as wild‐type (crimpy) fibers but differed in the layout of its cortical cells and in the relative proportions of keratin (K) and keratin‐associated proteins (KAPs). In the case of the crimp mutants (straight fibers), the orthocortex was distributed in a fragmented, annular ring, with some orthocortical cells near the central medulla, a pattern similar to that of straight hairs from humans and other mammals. Crimp mutant fibers were noted for the reduced abundance of some proteins in the high glycine–tyrosine class normally associated with the orthocortex, specifically the KAP6, KAP7, and KAP8 families, while proteins from the KAP16 and KAP19 were found in increased abundance. In addition to this, the type I keratin, K38, which is also associated with the orthocortex, was also found at lower abundance in the mutant fibers. Conversely, proteins from the ultra‐high sulfur class normally associated with the paracortex, specifically the KAP4 and KAP9 families, were found in higher abundance. [ABSTRACT FROM AUTHOR]

This study examined the role of earthworms in the stabilisation of soil organic carbon from livestock dung in a long-term mesocosm study, including its incorporation in deeper soil layers and association with particle size fractions. Two earthworm treatments were established, with the abundant and diverse treatment having 390 m−2 less epigeic Lumbricus rubellus, 2400 m−2 more endogeic Aporrectodea caliginosa and 220 m−2 more anecic Aporrectodea longa at the final sampling than the treatment dominated by epigeic species. The abundant and diverse earthworm treatment increased the decomposition of dung in the surface 20 mm, and doubled the amount of dung-derived C within the <250 µm size fractions at 20–75 mm depth compared to the epigeic treatment (4.8 vs. 9.8 g/kg soil, respectively). Earthworms have the ability to increase sequestration of C into smaller, and potentially more stable, size fractions. [ABSTRACT FROM AUTHOR]

New Zealand pastoral productivity relies heavily on biological nitrogen (N) fixation from rhizobia bacteria. Cadmium (Cd), present in pasture soils as an impurity in phosphate fertilisers, may have toxic effects on both plant growth and rhizobia activity. Effects of Cd on growth of seedlings of a white clover cultivar 'Grasslands Tribute', in the absence and presence of the N2-fixing Rhizobium leguminosarum bv. trifolii strain TA1, were assessed in vermiculite microcosm assays. The lowest observable effect concentrations resulting in significantly lower white clover shoot weights than those grown without Cd were 0.07 mg Cd kg−1 (measured as Ca(NO3)2-extractable Cd, Cdextractable) in the absence of Rhizobium, and 2.33 mg Cdextractable kg−1 for Rhizobium-inoculated seedlings. Shoot N content was unaffected in white clover exposed to <5 mg Cdextractable kg−1. The results indicate symbiosis with Rhizobium strain TA1 conferred tolerance to white clover 'Grasslands Tribute' against Cd toxicity, and that this symbiosis is unlikely to be adversely affected by Cd concentrations reported (<0.003 mg Cdextractable kg−1) in New Zealand pasture soils. [ABSTRACT FROM AUTHOR]

The nonspore-forming bacteriumSerratia entomophilamay be used to control the New Zealand grass grub (Costelytra giveni) but is sensitive to environmental stress and must be formulated to improve survival. Existing formulations require subsurface application limiting the area that can be treated. Formulations that allow delivery by broadcast methods are desirable to reduce application costs and increase the potential for aerial application to inaccessible areas. Two formulations were prepared for use in experiments examining the persistence and movement of inoculum through soil. When granules were applied to the soil surface, bacterial survival was negligible in uncoated core, but improved with increasing thickness of the coating. Both survival of bacteria and release into the soil were influenced by soil moisture content. Granules at <12% soil moisture showed high bacterial mortality and reduced delivery to the soil, while at 28% soil moisture most bacteria were released to the soil. There was a high level of survival of the applied bacteria within granules at 20% and 28% soil moisture. The formulations maintained viability ofS. entomophilain granules stored under ambient conditions for more than 6 months. In laboratory and field tests, the application of granules caused disease in the target grass grub larvae, whether application was applied to the surface or subsurface. In field trials, broadcast applied granules could produce equivalent disease to thin-coat granules drilled into the soil, but these levels of disease were associated with the occurrence of precipitation shortly after application. [ABSTRACT FROM AUTHOR]