Linda J. Thomson

Effects of ground cover (straw and compost) on the abundance of natural enemies and soil macro invertebrates in vineyards

1 Herbicides are commonly applied under grapevines in Australia to remove weeds and thereby to avoid water loss through transpiration.

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.

Shelterbelts in agricultural landscapes suppress invertebrate pests

The homogenous nature of agricultural landscapes generally reduces biodiversity of invertebrate species, but this can be partly offset by developing refuges at field margins. In Australia, shelterbelts are widely planted to provide protection for livestock and to counter salinity problems associated with rising water tables. Shelterbelts may also play a role in acting as reservoirs for organisms that are beneficial to pastures, although this has rarely been directly evaluated. We sampled invertebrates along transects running from replicated shelterbelts into pastures, and in glasshouse trials we tested the impact of the beneficial organisms from the shelterbelts on the collected pests. Contrary to popular views, numbers of pest mites and lucerne fleas were low within shelterbelts. Moreover, numbers were typically lower adjacent to shelterbelts compared with >30 m into the pasture, an effect that was much more apparent when shelterbelts carried a groundcover of high (>30 cm) grass. Numbers of predatory mites and spiders were higher in shelterbelts and in adjacent pasture when there was taller grass and higher grass cover in the shelterbelts. Samples of potential predators collected from a shelterbelt were more effective at suppressing pest mite numbers than those collected in pasture. Shelterbelts with ground cover appear to harbour a diversity of beneficial organisms that suppress pest numbers in adjacent pastures.

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.

Effective trapping methods for assessing invertebrates in vineyards

There is increasing interest in developing environmental management systems to ensure that agricultural industries are sustainable; invertebrate indicators provide one potential tool for monitoring sustainable production. As a first step in developing invertebrate indicators for viticulture, we compare the efficiency of 3 common trapping methods in assessing populations of relevant orders of invertebrates. Yellow sticky traps were more effective in trapping Hymenoptera, Thysanoptera, Hemiptera, Diptera, Araneae and Coleoptera; transparent sticky traps were best for Lepidoptera and Neuroptera; and pitfall traps for Collembola and the family Formicidae. Numbers collected differed among months and December was the best month, overall, for trapping. Preliminary guidelines are developed for assessing key orders. While several methods are required for assessing invertebrate biodiversity, most orders can be sampled with a single method, particularly the yellow sticky trap. Our results indicate that changes in numbers of beneficial orders, due to changes in management practices, can be detected. Power analyses suggest a relatively small number of yellow sticky traps would be sufficient to detect changes of around 30%, or greater.

Identifying signature of chemical applications on indigenous and invasive nontarget arthropod communities in vineyards

Communities of arthropods providing ecosystem services (e.g., pest control, pollination, and soil nutrient cycling) to agricultural production systems are influenced by pesticide inputs, yet the impact of pesticide applications on nontarget organisms is normally evaluated through standardized sets of laboratory tests involving individual pesticides applied to a few representative species. By combining season-long pesticide applications of various insecticides and fungicides into a metric based on the International Organization for Biological and Integrated Control (IOBC) toxicity ratings, we evaluate season-long pesticide impacts on communities of indigenous and exotic arthropods across 61 vineyards assessed for an entire growing season. The composition of arthropod communities, identified mostly at the family level, but in some cases at the species level, was altered depending on season-long pesticide use. Numbers of mostly indigenous parasitoids, predatory mites, and coccinellids in the canopy, as well as carabid/tenebrionid beetles and some spider families on the ground, were decreased at higher cumulative pesticide metric scores. In contrast, numbers of one invasive millipede species (Ommatoiulus moreletti Lucas, Julida: Julidae) increased under higher cumulative pesticide metric scores. These changing community patterns were detected despite the absence of broad-spectrum insecticide applications in the vineyards. Pesticide effects were mostly due to indoxacarb and sulphur, applied as a fungicide. The reduction of beneficial arthropods and increase in an invasive herbivorous millipede under high cumulative pesticide metric scores highlights the need to manage nontarget season-long pesticide impacts in vineyards. A cumulative pesticide metric, based on IOBC toxicity ratings, provides a way of assessing overall toxicity effects, giving managers a means to estimate and consider potential negative season-long pesticide impacts on ecosystem services provided through arthropod communities.

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.

Ecologically Sustainable Chemical Recommendations for Agricultural Pest Control

Abstract Effective pest control remains an essential part of food production, and it is provided both by chemicals and by natural enemies within agricultural ecosystems. These methods of control are often in conflict because of the negative impact of chemicals on natural enemies. There are already well-established approaches such as those provided by the International Organization for Biological and Integrated Control–Pesticides and Beneficial Organisms for testing, collecting, and publishing information on responses of natural enemies to chemicals based on laboratory responses of specific organisms; however, these tests do not assess the cumulative impact of chemical inputs across an entire season or consider impacts on the complex communities of natural enemies that can provide effective pest control on a farm. Here, we explore the potential of different approaches for assessing the impact of chemicals on agricultural ecosystems and we propose a simple metric for sustainable chemical use on farms that minimizes overall impact on beneficial groups. We suggest ways in which the effectiveness of metrics can be extended to include persistence and habitat features. Such metrics can assist farmers in developing targets for sustainable chemical use as demonstrated in the viticultural industry.

Using invertebrate bioindicators to assess agricultural sustainability in Australia: proposals and current practices

The papers in this special issue, ‘Using Invertebrate Bioindicators to Assess Agricultural Sustainability in Australia: Proposals and Current Practices’, highlight the diversity of invertebrates in agricultural environments and associated environments, and the varied roles they play in agricultural production. The papers demonstrate the various ways that the constitution of the invertebrate fauna can change rapidly in response to environmental inputs such as chemicals and landscape management. Given these factors, invertebrates show enormous potential to be used as indicators of sustainability in agriculture. However, this potential remains to be realised.

Influence of native ants on arthropod communities in a vineyard

1 Ants can have a range of effects on arthropods in crops, including suppressing herbivores such as caterpillars. However, ants can also increase hemipteran densities while reducing natural enemy numbers. In vineyard ecosystem, the effects of native ants and their interactions with other arthropods are poorly understood. 2 An ant‐exclusion experiment was designed to test the impact of native ants on both canopy and ground arthropods concurrently. The potential influence of ants on predation and parasitism of light brown apple moth (LBAM) eggs, a grape pest, was also examined. Adult grapevine scale insects and earwigs under bark were counted after a season of ant‐exclusion. 3 Among 23 ground ant species collected, six were found to forage in the canopy, with two Iridomyrmex species being the most commonly encountered. 4 There was no difference in the abundance of most arthropod orders and feeding groups between ant‐excluded and control vines, although ground spiders were more abundant under ant‐excluded vines, despite increased ground ant foraging pressure. LBAM egg parasitism and predation were low and probably affected by weather and other arthropods. Ant exclusion did not reduce survival of scale insects, although the distribution and abundance of scale insects were negatively associated with earwigs. 5 In conclusion, native ants did not consistently suppress arthropod assemblages, including natural enemies, and they did not promote the survival of scale insects. Interactions among native ant species within a vineyard might minimize their effects on other arthropods, although this needs further study.