David Sharley

The effects of soil tillage on beneficial invertebrates within the vineyard

1 Tillage, commonly used in agroecosystems, can influence the abundance of invertebrates through factors such as habitat change and food availability.

Effects of Native Grass Cover Crops on Beneficial and Pest Invertebrates in Australian Vineyards

ABSTRACT Indigenous cover crops have the potential to promote an increase in natural enemies providing fortuitous control of pest species and other ecosystem services. We test this idea in a vineyard in south eastern Australia, where reduced water availability because of drought coupled with increased temperatures has generated interest in sustainable alternatives to the exotic perennial cover crops commonly planted. Three endemic perennial cover crops, comprising the grasses Austrodanthonia richardsonii and Chloris truncata and a mix of two saltbushes (Atriplex semibaccata and Atriplex suberecta) were established as cover crops and compared with introduced oats (Avena sativa). Abundance of a range of predators and parasitoids was higher in vines with native cover crops compared with the oat control. In addition, predation levels of sentinel eggs of a common vineyard pest, light brown apple moth (Epiphyas postvittana), were increased in the native cover crops. However, the native cover crops also increased the abundance of some potential pest species. Native plants therefore have potential to increase abundance of beneficial invertebrates that assist in pest control, but need to be used carefully to ensure that they do not increase local pest problems.

Detritivores as indicators of landscape stress and soil degradation

Detritivores are small- to medium-sized invertebrates that comminute and break down organic materials such as leaves, twigs and roots, especially within or upon the soil surface, or nearby. Detritivores constitute the majority of the invertebrate biomass pyramid in most environments and provide a key role in organic matter turnover; they also provide alternative food for polyphagous predators that can be active in pest control on crops. Many arthropod taxa are detritivores in soil and litter layers. Here, we focus on the bioindicator potential of three key detritivore groups: slaters, millipedes and oribatid mites. There are possibly 300 species of slaters (terrestrial isopods or Oniscidea) in Australia with 13 of these being introduced, mostly from north-western Europe. These non-native species are the dominant species in disturbed environments such as intensively managed forests and agricultural fields. Slaters are promising indicators of landscape disturbance, soil contamination and tillage. Millipedes are potentially important indicators of stress in agricultural landscapes, given their sensitivity to litter and soil moisture gradients and to physical and chemical perturbations. However, because there is a close association between the millipede fauna and moist plant communities in Australia, they are generally absent from drier landscapes and, therefore, their use as bioindicators in agricultural environments here is problematic. An exception to this association is the increasingly ubiquitous introduced Black Portuguese millipede. This species is tolerant of much drier conditions than most natives, and is likely to change the nature of nutrient cycling processes in pastures and native grasslands in much of southern Australia. Oribatid mites are present in all Australian terrestrial ecosystems. The few studies that have examined their response to disturbance and land use in Australia are consistent with the body of work conducted outside Australia. This consistent response means that the oribatids may be developed as indicators in agricultural, pasture and forested environments. However, the paucity of information on oribatids over appropriate spatial scales in Australia makes the use of this group extremely difficult at this time.

Effects of sediment quality on macroinvertebrates in the Sunraysia region of the Murray-Darling Rivers, Australia.

A field-based microcosm approach was tested to identify deterioration of sediment quality in waterways using freshwater macroinvertebrates. The method can potentially identify the nature of contaminants based on species-specific responses. Sediments were collected from the Murray and Darling Rivers and irrigation drains within the Sunraysia region of south-eastern Australia and compared to non-polluted reference sediment. Clean sediments were also spiked with fertiliser to test whether nutrients affected the aquatic fauna. Seven of the eight sediments from the Sunraysia region had a negative impact on the macroinvertebrates, in particular sediment from the Darling River, which supported an impoverished fauna. Three species of chironomid showed varied responses to sediment quality and, although it was hypothesised that nutrients may have impacted on the macroinvertebrate fauna, the results suggest that other pollutants are also involved. The field-based microcosm method proved effective for determining the impact of sediment quality on indigenous macroinvertebrates.

Beneficial organisms as bioindicators for environmental sustainability in the grape industry in Australia

Increased biodiversity is being promoted as an important aim for Australian agriculture, but the measurement of biodiversity is problematic and often not practical. An alternative involves the development of surrogate indicators for biodiversity on farms that have direct links to production. One group of organisms that may perform this function in vineyards is the beneficial invertebrates that have a direct impact on pest abundance. If we can identify the effects of common management practices on invertebrates that are important in the wine industry, we can identify target organisms whose presence suggests good and sustainable practice. Here we identify key invertebrates, both pests and natural enemies, in grape production, the effects of some management practices on these invertebrates, and suggest steps to develop these invertebrates into sustainability indicators for the viticulture industry.

Detecting long-term temporal trends in sediment-bound trace metals from urbanised catchments.

The shift from rural lifestyles to urban living has dramatically altered the way humans interact and live across the globe. With over 50% of the worlds populations living within cities, and significant increases expected over the next 50 years, it is critical that changes to social, economic and environmental sustainability of cities globally be implicit. Protecting and enhancing aquatic ecosystems, which provide important ecosystem services, is challenging. A number of factors influence pollutants in urban waterways including changes in land-use, impervious area and stormwater discharges, with sediment-bound pollution a major issue worldwide. This work aimed to investigate the spatial and temporal distribution of trace metals in freshwater sediments from six urbanised catchment over a 30-year period. It provides an estimate of pollution using a geoaccumulation index and examines possible toxicity using a probable effect concentration quotient (mPECq). Results showed significant temporal changes in metal concentrations over time, with lead generally decreasing in all but one of the sites, attributed to significant changes in environmental policies and the active elimination of lead products. Temporal changes in other metals were variable and likely dependent on site-specific factors. While it is likely that diffuse pollution is driving changes in zinc, for metals such as lead, chromium and copper, it is likely that watershed landuse and/or point sources are more important. The results clearly indicated that changes to watershed landuse, environmental policy and pollution abatement programs are all driving changes in sediment quality, highlighting the utility of long-term sediment monitoring for assessment of urban watershed condition. While this study has demonstrated the utility of detecting long-term changes in metal concentrations, this approach could easily be adapted to detect and assess future trends in other hydrophobic contaminants and emerging chemicals of concern, such as synthetic pyrethroids, providing essential information for the protection of catchment.

Potentially Toxic Concentrations of Synthetic Pyrethroids Associated with Low Density Residential Land Use

Trace organic compounds associated with human activity are now ubiquitous in the environment. As the population becomes more urbanised and the use of pesticides and person care products continues to increase, urban waterways are likely to receive higher loads of trace organic contaminants with unknown ecological consequences. To establish the extent of trace organic contamination in urban runoff, concentrations of emerging chemicals of concern were determined in sediments from 99 urban wetlands in and around Melbourne, Australia between February and April, 2015. As a preliminary estimation of potential risks to aquatic biota, we compared measured concentrations with thresholds for acute and chronic toxicity, and modelled toxic units as a function of demographic and land use trends. The synthetic pyrethroid insecticide bifenthrin was common and widespread, and frequently occurred at concentrations likely to cause toxicity to aquatic life. Personal care products DEET and triclosan were common and widely distributed, while the herbicides diuron and prometryn, and the fungicides pyrimethanil and trifloxystrobin occurred less frequently. Toxic unit modelling using random forests found complex and unexpected associations between urban land uses and trace organic concentrations. Synthetic pyrethroid insecticides were identified as emerging compounds of concern, particularly bifenthrin. In contrast with previous surveys, the highest bifenthrin concentrations were associated with lower housing and population density, implicating low-density residential land use in bifenthrin contamination. We discuss the implications for pesticide regulation and urban wetland management in a global context.

A short work-flow to effectively source faecal pollution in recreational waters – A case study

Microbial pollution of recreational waters poses a significant public health risk which, unless mitigated, will continue to increase with population growth. Water managers must implement strategies to accurately discriminate and source human from animal faecal contamination in complex urbanised environments. Our case-study used a new combination of chemical (i.e. ammonia) and microbial (i.e. Escherichia coli, Bacteroides spp.) faecal monitoring tools in a targeted multi-tiered approach to quickly identify pollution hot-spots and track high-risk subterranean stormwater drains in real-time. We successfully located three point sources of human faecal pollution (both episodic and constant pollution streams) within 11 catchments in a total monitoring time of four months. Alternative approaches for obtaining such fine-scale accuracy are typically labour intensive and require expensive equipment.

Metabolomic Profiles of a Midge (Procladius villosimanus, Kieffer) Are Associated with Sediment Contamination in Urban Wetlands

Metabolomic techniques are powerful tools for investigating organism-environment interactions. Metabolite profiles have the potential to identify exposure or toxicity before populations are disrupted and can provide useful information for environmental assessment. However, under complex environmental scenarios, metabolomic responses to exposure can be distorted by background and/or organismal variation. In the current study, we use LC-MS (liquid chromatography-mass spectrometry) and GC-MS (gas chromatography-mass spectrometry) to measure metabolites of the midge Procladius villosimanus inhabiting 21 urban wetlands. These metabolites were tested against common sediment contaminants using random forest models and metabolite enrichment analysis. Sediment contaminant concentrations in the field correlated with several P. villosimanus metabolites despite natural environmental and organismal variation. Furthermore, enrichment analysis indicated that metabolite sets implicated in stress responses were enriched, pointing to specific cellular functions affected by exposure. Methionine metabolism, sugar metabolism and glycerolipid metabolism associated with total petroleum hydrocarbon and metal concentrations, while mitochondrial electron transport and urea cycle sets associated only with bifenthrin. These results demonstrate the potential for metabolomics approaches to provide useful information in field-based environmental assessments.