Acute toxicity effects of pesticides on beneficial organisms - Dispelling myths for a more sustainable use of chemicals in agricultural environments.

Agricultural practitioners, researchers and policymakers are increasingly advocating for integrated pest management (IPM) to reduce pesticide use while preserving crop productivity and profitability. Using selective pesticides, putatively designed to act on pests while minimising impacts on off-target organisms, is one such option - yet evidence of whether these chemicals control pests without adversely affecting natural enemies and other beneficial species (henceforth beneficials) remains scarce. At present, the selection of pesticides compatible with IPM often considers a single (or a limited number of) widely distributed beneficial species, without considering undesired effects on co-occurring beneficials. In this study, we conducted standardised laboratory bioassays to assess the acute toxicity effects of 20 chemicals on 15 beneficial species at multiple exposure timepoints, with the specific aims to: (1) identify common and diverging patterns in acute toxicity responses of tested beneficials; (2) determine if the effect of pesticides on beetles, wasps and mites is consistent across species within these groups; and (3) assess the impact of mortality assessment timepoints on International Organisation for Biological Control (IOBC) toxicity classifications. Our work demonstrates that in most cases, chemical toxicities cannot be generalised across a range of beneficial insects and mites providing biological control, a finding that was found even when comparing impacts among closely related species of beetles, wasps and mites. Additionally, we show that toxicity impacts increase with exposure length, pointing to limitations of IOBC protocols. This work challenges the notion that chemical toxicities can be adequately tested on a limited number of 'representative' species; instead, it highlights the need for careful consideration and testing on a range of regionally and seasonally relevant beneficial species.

Achieving conservation and restoration outcomes through ecologically beneficial aquaculture.

A range of conservation and restoration tools are needed to safeguard the structure and function of aquatic ecosystems. Aquaculture, the culturing of aquatic organisms, often contributes to the numerous stressors that aquatic ecosystems face, yet some aquaculture activities can also deliver ecological benefits. We reviewed the literature on aquaculture activities that may contribute to conservation and restoration outcomes, either by enhancing the persistence or recovery of one or more target species or by moving aquatic ecosystems toward a target state. We identified 12 ecologically beneficial outcomes achievable via aquaculture: species recovery, habitat restoration, habitat rehabilitation, habitat protection, bioremediation, assisted evolution, climate change mitigation, wild harvest replacement, coastal defense, removal of overabundant species, biological control, and ex situ conservation. This list may be expanded as new applications are discovered. Positive intentions do not guarantee positive ecological outcomes, so it is critical that potentially ecologically beneficial aquaculture activities be evaluated via clear and measurable indicators of success to reduce potential abuse by greenwashing. Unanimity on outcomes, indicators, and related terminology will bring the field of aquaculture-environment interactions into line with consensus standards in conservation and restoration ecology. Broad consensus will also aid the development of future certification schemes for ecologically beneficial aquaculture.

Se necesita una gama de herramientas de conservación y restauración para salvaguardar la estructura y función de los ecosistemas acuáticos. La acuacultura (el cultivo de organismos acuáticos) generalmente contribuye a los numerosos estresantes que soportan los ecosistemas acuáticos, aunque algunas actividades de la acuacultura también pueden proporcionar beneficios ecológicos. Revisamos la literatura sobre las actividades de acuacultura que pueden contribuir a los resultados de conservación y restauración, ya sea al incrementar la persistencia o recuperación de una o más especies objetivo o al llevar a los ecosistemas acuáticos hacia un estado objetivo. Identificamos doce resultados con beneficios ecológicos que pueden lograrse con la acuacultura: recuperación de la especie, recuperación del hábitat, restauración del hábitat, rehabilitación del hábitat, protección del hábitat, bioreparación, evolución asistida, mitigación del cambio climático, sustitución de la captura silvestre, defensa costera, eliminación de las especies sobreabundantes, control biológico y conservación ex situ. Esta lista puede expandirse conforme se descubren nuevas aplicaciones. Las intenciones positivas no garantizan resultados ecológicos positivos, así que es importante que se evalúen las actividades de acuacultura con un posible beneficio ecológico por medio de indicadores del éxito claros y medibles para reducir el abuso potencial por ecoblanqueo o greenwashing. La unanimidad en los resultados, indicadores y terminología relacionada armonizará las interacciones entre la acuacultura y el ambiente con los estándares de la conservación y la ecología de la restauración. Un consenso generalizado también ayudará con el desarrollo de futuros esquemas de certificación para la acuacultura con beneficios ecológicos. Obtención de resultados de conservación y restauración a través de la acuacultura con beneficios ecológicos.

Toxicity of Insecticides and Miticides to Natural Enemies in Australian Grains: A Review.

Continued prophylactic chemical control to reduce pest populations in Australian grain farming systems has limited the effectiveness of biological control via natural enemies in crops within an integrated pest management (IPM) framework. While a variety of data is available to infer potential non-target effects of chemicals on arthropod natural enemies, much of it may be irrelevant or difficult to access. Here, we synthesise the literature relevant to Australian grain crops and highlight current knowledge gaps for potential future investment. A range of testing methodologies have been utilised, often deviating from standardised International Organization for Biological Control (IOBC) protocols. Consistent with findings from over 30 years ago, research has continued to occur predominantly at laboratory scales and on natural enemy families that are easily reared or commercially available. There is a paucity of data for many generalist predators, in particular for spiders, hoverflies, and rove and carabid beetles. Furthermore, very few studies have tested the effects of seed treatments on natural enemies, presenting a significant gap given the widespread global use of neonicotinoid seed treatments. There is a need to validate results obtained under laboratory conditions at industry-relevant scales and also prioritise testing on several key natural enemy species we have identified, which should assist with the adoption of IPM practices and decrease the reliance on broad-spectrum chemicals.

Regional and seasonal activity predictions for fall armyworm in Australia.

Since 2016, the fall armyworm (FAW), Spodoptera frugiperda, has undergone a significant range expansion from its native range in the Americas, to continental Africa, Asia, and in February 2020, mainland Australia. The large dispersal potential of FAW adults, wide host range of immature feeding stages, and unique environmental conditions in its invasive range creates large uncertainties in the expected impact on Australian plant production industries. Here, using a spatial model of population growth and spread potential informed by existing biological and climatic data, we simulate seasonal population activity potential of FAW, with a focus on Australia's grain production regions. Our results show that, in Australia, the large spread potential of FAW will allow it to exploit temporarily favourable conditions for population growth across highly variable climatic conditions. It is estimated that FAW populations would be present in a wide range of grain growing regions at certain times of year, but importantly, the expected seasonal activity will vary markedly between regions and years depending on climatic conditions. The window of activity for FAW will be longer for growing regions further north, with some regions possessing conditions conducive to year-round population survival. Seasonal migrations from this permanent range into southern regions, where large areas of annual grain crops are grown annually, are predicted to commence from October, i.e. spring, with populations subsequently building up into summer. The early stage of the FAW incursion into Australia means our predictions of seasonal activity potential will need to be refined as more Australian-specific information is accumulated. This study has contributed to our early understanding of FAW movement and population dynamics in Australia. Importantly, the models established here provide a useful framework that will be available to other countries should FAW invade in the future. To increase the robustness of our model, field sampling to identify conditions under which population growth occurs, and the location of source populations for migration events is required. This will enable accurate forecasting and early warning to farmers, which should improve pest monitoring and control programs of FAW.

Parasites under pressure: salmon lice have the capacity to adapt to depth-based preventions in aquaculture.

The evolution of pesticide resistance has driven renewed interest in non-chemical pest controls in agriculture. Spatial manipulations (physical barriers and fallowing, for example) can be an effective method of prevention, but these too might impose selection and cause rapid adaptation in pests. In salmon aquaculture, various non-chemical approaches have emerged to combat parasitic salmon lice (Lepeophtheirus salmonis) - a major pest with clear signs of evolved chemical resistance. 'Depth-based' preventions, now widely implemented, reduce infestation rates by physically segregating salmon from lice in their infective copepodid stage occurring in surface waters. Copepodids distributed deeper in the water column, however, can bypass these barriers and infest farms. If swimming depth is a heritable trait, we may see rapid evolutionary shifts in response to widespread depth-based prevention. We collected lice from Norwegian salmon farms and assayed more than 11,250 of their laboratory-reared offspring across 37 families. The vertical distributions of copepodids were measured using experimental water columns pressurised to simulate conditions at 0, 5 and 10 m depths. We demonstrated that lice respond strongly to hydrostatic pressure: an increase in pressure doubled the number of lice that migrated to the top of columns. There was also a large effect of family on this response, with the percentage of lice ascending to the top of pressurised columns ranging from 17 to 79% across families. Families with a weak swimming response to pressure are expected to occur deeper in the water column and so be more likely to infest farms employing depth-based preventions. If this between-family variation reflects genetic variation, then the parasite population may have the capacity to adapt to preventative measures. Such adaptation would have important commercial and ecological implications.

Effect of cleaner fish on sea lice in Norwegian salmon aquaculture: a national scale data analysis.

The salmon aquaculture industry has adopted the use of invertivorous 'cleaner fishes' (CF) for biological control of sea louse infestations on farmed salmon. At present, ~50 million CF are used annually in Norway alone, with variable success in experimental and industrial contexts. We used a national scale database of louse counts, delousing treatments and CF stocking events on Norwegian salmon farms to test for evidence of CF efficacy at 488 sites that completed a grow-out cycle within 2016-2018. Our analysis revealed that sites using more CF over the duration of a grow-out cycle did not have fewer lice on average, likely because CF use is reactive and in proportion to the scale of the louse problem. Over time within sites, we found that (i) sites using more CF early in the grow-out cycle were able to wait slightly longer (conservatively, a 5.2 week delay with 5000 CF stocked week-1) before conducting the first delousing treatment, and (ii) CF stocking events were followed, on average, by a small reduction in louse population growth rates. However, both effects were small and highly variable, and louse population growth rates remained positive on average, even when large numbers of CF were used (tens of thousands per site). Moreover, effects of CF on louse density tended to be short-lived, likely reflecting mortality and escape of stocked CF. Overall, the data indicate that while some sites consistently obtain good results from CF, there is also widespread suboptimal use. A better understanding of factors affecting CF efficacy in commercial sea cages is required to inform legislation and drive more efficient and ethical use of CF by the salmon aquaculture industry.

Lowering treatment temperature reduces salmon mortality: a new way to treat with hydrogen peroxide in aquaculture.

BACKGROUND: Hydrogen peroxide (H2 O2 ) baths are widely used to reduce numbers of salmon lice on farmed Atlantic salmon. Fish mortalities often occur after baths, with warmer temperatures increasing lethality. We tested whether mortality could be reduced and lice removal efficacy maintained by lowering bath temperatures relative to ambient temperatures. Post-smolt salmon infected with lice were held at 10, 13 or 16 °C, and treated with 1.5 g/L H2 O2 for 20 min at equal or lower bath temperatures of 7, 10 or 13 °C. RESULTS: Salmon mortality decreased as ambient and bath temperatures decreased. No mortality occurred when fish at 13 °C were treated at 7 °C. For ambient temperatures of 16 °C, the number of lice remaining was reduced by four-fold when treated at 7 °C compared with 13 °C. All treatments in which mortality was zero had similar efficacies regardless of bath temperature. CONCLUSION: We took salmon from warmer to colder temperatures to determine the optimum bathing temperature to prevent mortality. A temperature of 7 °C was optimal when treating with 1.5 g/L of H2 O2 , as mortality was zero and pre-adult lice removal was unchanged. By manipulating temperature, we developed a new method of H2 O2 bathing that reduces mortality. When ambient temperatures are >10 °C, we recommend that the industry decrease H2 O2 bath temperatures. © 2017 Society of Chemical Industry.