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Resistance to pesticides is typically identified via laboratory bioassays after field control failures are observed, but the results of such assays are rarely validated through experiments under field conditions. Such validation is particularly important when only a low-to-moderate level of resistance is detected in the laboratory. Here we undertake such a validation for organophosphate resistance in the agricultural pest mite Halotydeus destructor, in which low-to-moderate levels of resistance to organophosphorus pesticides have evolved in Australia. Using data from laboratory bioassays, we show that resistance to the organophosphate chlorpyrifos is higher (around 100-fold) than resistance to another organophosphate, omethoate (around 7-fold). In field trials, both these chemicals were found to effectively control pesticide-susceptible populations of H. destructor. However, when applied to a resistant mite population in the field, the effectiveness of chlorpyrifos was substantially decreased. In contrast, omethoate remained effective when tested alone or as a mixture with chlorpyrifos. We also show that two novel (non-pesticide) treatments, molasses and wood vinegar, are ineffective in controlling H. destructor when sprayed to pasture fields at rates of 4 L/ha. These findings suggest a close link between levels of resistance quantified through laboratory bioassays and the field effectiveness of pesticides; however, in the case of H. destructor, this does not necessarily mean all field populations possessing organophosphate resistance will respond similarly given the potentially complex nature of the underlying resistance mechanism(s).

Chemical resistance in pest organisms threatens global food security and human health, yet resistance issues are mostly dealt with reactively. Predictive models of resistance risk provide an avenue for field practitioners to implement proactive pest management but require knowledge of factors that drive resistance evolution. Despite the importance of chemical selection pressure on resistance evolution, poor availability of chemical usage data has limited the use of a general multi-species measure of selection pressure in predictive models. We demonstrate the use of pesticide product registrations as a predictor of resistance status and potential proxy of chemical selection pressure. Pesticide product registrations were obtained for 427 USA and 209 Australian agricultural arthropod pests, for 42 and 39 chemical Mode of Action (MoA) groups, respectively. We constructed Bayesian logistic regressions of resistance status as a function of the number of pesticide product registrations and two ecological traits, phagy and voltinism. Our models were well-supported with demonstrated power to discriminate between resistant and susceptible observations in both USA and Australian species sets using cross-validation. Importantly, we observed strong support for a positive association between pesticide products and resistance status. Our work expands the horizon for proactive management by quantitatively linking a proxy for selection pressure on pest species to different chemical MoAs. This proxy for selection pressure can be combined with ecological information to predict the resistance risk in agricultural pests. Because pesticide product registrations can typically be derived from publicly available data, we believe there is broad applicability to other agricultural pests such as weeds and fungi, and to other geographical regions beyond the USA and Australia.

Chemicals are widely used to protect field crops against aphid pests and aphid-borne viral diseases. One such species is Myzus persicae (Sulzer), a global pest that attacks a broad array of agricultural crops and transmits many economically damaging plant viruses. This species has evolved resistance to a large number of insecticide compounds as a result of widespread and repeated chemical use in many parts of the world. In this study, we investigated the evolution of resistance to a new plant protection product, spirotetramat, following reported chemical control failures.Our study provides clear phenotypic and genotypic evidence of spirotetramat resistance in populations of M. persicae from Australia. We show there is cross-resistance to other insecticides within the same chemical group, namely spiromesifen and spirodiclofen. We also demonstrate that resistance is associated with the previously reported mutation, A2226V in the target site of spirotetramat, acetyl-CoA carboxylase. Our genetic analysis found all resistant M. persicae populations belong to the same multi-locus clonal type and carry the A2226V mutation, which appears to be inherited as a dominant trait in this species.Our findings provide new insight into the resistance conferred by A2226V and have implications for the control of M. persicae in Australia and worldwide. A diagnostic assay developed in this study should serve as a valuable tool for future resistance monitoring and to support the implementation of pest management strategies. © 2022 The Authors. Pest Management Science published by John WileySons Ltd on behalf of Society of Chemical Industry.

While several agricultural fungicides are known to directly affect invertebrate pests, including aphids, the mechanisms involved are often unknown. One hypothesis is that fungicides with antibacterial activity suppress bacterial endosymbionts present in aphids which are important for aphid survival. Endosymbiont-related effects are expected to be transgenerational, given that these bacteria are maternally inherited. Here, we test for these associations using three fungicides (chlorothalonil, pyraclostrobin and trifloxystrobin) against the bird cherry-oat aphid, Rhopalosiphum padi, using a microinjected strain that carried both the primary endosymbiont Buchnera and the secondary endosymbiont Rickettsiella.We show that the fungicide chlorothalonil did not cause an immediate effect on aphid survival, whereas both strobilurin fungicides (pyraclostrobin and trifloxystrobin) decreased survival after 48 h exposure. However, chlorothalonil substantially reduced the lifespan and fecundity of the F1 generation. Trifloxystrobin also reduced the lifespan and fecundity of F1 offspring, however, pyraclostrobin did not affect these traits. None of the fungicides consistently altered the density of Buchnera or Rickettsiella in whole aphids.Our results suggest fungicides have sublethal impacts on R. padi that are not fully realized until the generation after exposure, and these sublethal impacts are not associated with the density of endosymbionts harbored by R. padi. However, we cannot rule out other effects of fungicides on endosymbionts that might influence fitness, like changes in their tissue distribution. We discuss these results within the context of fungicidal effects on aphid suppression across generations and point to potential field applications. © 2022 Society of Chemical Industry.

Endosymbiotic bacteria that live inside the cells of insects are typically only transmitted maternally and can spread by increasing host fitness and/or modifying reproduction in sexual hosts. Transinfections of Wolbachia endosymbionts are now being used to introduce useful phenotypes into sexual host populations, but there has been limited progress on applications using other endosymbionts and in asexual populations. Here, we develop a unique pathway to application in aphids by transferring the endosymbiont Rickettsiella viridis to the major crop pest Myzus persicae . Rickettsiella infection greatly reduced aphid fecundity, decreased heat tolerance, and modified aphid body color, from light to dark green. Despite inducing host fitness costs, Rickettsiella spread rapidly through caged aphid populations via plant-mediated horizontal transmission. The phenotypic effects of Rickettsiella were sensitive to temperature, with spread only occurring at 19 °C and not 25 °C. Body color modification was also lost at high temperatures despite Rickettsiella maintaining a high density. Rickettsiella shows the potential to spread through natural M. persicae populations by horizontal transmission and subsequent vertical transmission. Establishment of Rickettsiella in natural populations could reduce crop damage by modifying population age structure, reducing population growth and providing context-dependent effects on host fitness. Our results highlight the importance of plant-mediated horizontal transmission and interactions with temperature as drivers of endosymbiont spread in asexual insect populations.

Context The Australian dairy industry largely relies on grass-based pastures to feed cattle, yet these pastures also host dynamic invertebrate communities that can damage or benefit pasture productivity. While Australian dairy managers have traditionally focused on invertebrates that damage pastures (i.e. pests), invertebrates that provide valuable ecosystem services by acting as natural enemies to pests or delivering other beneficial functions (e.g. nutrient cycling) have received less attention. Aim Surveying the natural enemies and other beneficial invertebrate communities in pastures across seven Australian dairy regions and to explore how environmental and farm management factors impact these. Method Fifty seven pastures samples were collected during spring and autumn over two years. In doing so, we identified and counted 2 661 315 invertebrates or invertebrate colonies. Key results We found natural enemies and other beneficial invertebrate communities have a similar taxonomic composition across regions, with a small number of taxa dominating all regions, and rainfall the most consistent environmental driver in the abundance of these dominant taxa. Conclusions Farm management strategies to maintain or promote existing communities of beneficial taxa will likely be similar across regions. Associations between invertebrate communities suggest pest communities may indirectly impact the abundance and/or diversity of natural enemies and other beneficial invertebrates. Implications Although still an early step, our findings provide important baseline information that can be used to provide dairy managers with strategies to promote communities of beneficial invertebrates, and consequently maximise the benefits these invertebrates provide.

Bryobia (Koch) mites belong to the economically important spider mite family, the Tetranychidae, with130 species described worldwide. Due to taxonomic difficulties and most species being asexual, species identification relies heavily on genetic markers. Multiple putative Bryobia mite species have been identified attacking pastures and grain crops in Australia. In this study, we collected 79 field populations of Bryobia mites and combined these with 134 populations that were collected previously. We characterised taxonomic variation of mites using 28S rDNA amplicon-based DNA metabarcoding using next-generation sequencing approaches and direct Sanger sequencing. We then undertook species distribution modelling of the main genetic lineages and examined the chemical responses of multiple field populations.We identified 47 unique haplotypes across all mites sampled that grouped into four distinct genetic lineages. These lineages have different distributions, with three of the four putative lineages showing different climatic envelopes, as inferred from species distribution modelling. Bryobia mite populations also showed different responses to a widely used insecticide (the organophosphate, omethoate), but not to another chemical (the pyrethroid, bifenthrin) when examined using laboratory bioassays.Our findings indicate that cryptic diversity is likely to complicate the formulation of management strategies for Bryobia mites. Although focussed on Australia, this study demonstrates the challenges of studying Bryobia and highlights the importance of further research into this complex group of mites across the world. © 2022 The Authors. Pest Management Science published by John WileySons Ltd on behalf of Society of Chemical Industry.

The Spotted Lantern Fly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is a sap feeding pest native to southeast Asia that has become a global biosecurity threat following invasions into South Korea, Japan, and the United States in the last two decades. Environmental niche modelling has demonstrated considerable potential for further range expansions, including into Australia and Europe. Further analysis on the potential seasonal life-history and survival of this pest in its invasive range can inform monitoring programs and is a next step in biosecurity preparedness. Here, we incorporated eco-physiological information on the development and survival of SLF life stages across temperature regimes. Using gridded climatic data, we then mapped the developmental sequence of SLF across ranges already occupied in China, South Korea, and the United States, as well as uninvaded ranges in Australia and Europe. The model was able to capture global observations of the seasonal appearance of SLF and highlight regional and seasonal vulnerabilities in regions at risk of invasion. Policy makers can use these results to make science-based biosecurity decisions and target preparedness activities through improved life-history predictions in its invasive range.

The redlegged earth mite, Halotydeus destructor, is an economically important pest of winter field crops and pastures in Australia, and has evolved field resistance to pyrethroid chemicals through a polymorphism in the voltage-gated parasodium channel leading to knockdown resistance (kdr). In this study, we quantified the rate of reversion to susceptibility of partially resistant H. destructor populations under field conditions in the absence of pesticide exposure. This was conducted over multiple years at two geographically distant locations with mite populations known to possess pyrethroid resistance. Fitness costs associated with pyrethroid resistance were identified through reductions in the frequency of kdr resistance alleles in the absence of pesticides. This was assessed using an amplicon sequencing approach targeting known resistance alleles. We also found that resistance can increase rapidly in frequency after only a single pyrethroid application in the field. Our results highlight that, once established in H. destructor populations, pyrethroid resistance will not easily be lost even after several years, emphasizing the importance of limiting the evolution of resistance in the first place. This helps to explain why pyrethroid resistance in H. destructor continues to persist at very high frequencies in the field and continues to expand within Australia despite the existence of fitness costs. Understanding field fitness costs associated with pesticide resistance is important when devising resistance management strategies for this pest.

The redlegged earth mite, Halotydeus destructor (Tucker, 1925: Trombidiformes, Eupodoidea, Penthaleidae), is an invasive mite species. In Australia, this mite has become a pest of winter pastures and grain crops. We report the complete mitogenome for H. destructor, the first to represent the family Penthaleidae, superfamily Eupodoidea. The mitogenome of H. destructor is 14,691 bp in size, and has a GC content of 27.87%, 13 protein‐coding genes, two rRNA genes, and 22 tRNA genes. We explored evolutionary relationships of H. destructor with other members of the Trombidiformes using phylogenetic analyses of nucleotide sequences and the order of protein‐coding and rRNA genes. We found strong, consistent support for the superfamily Tydeoidea being the sister taxon to the superfamily Eupodoidea based on nucleotide sequences and gene arrangements. Moreover, the gene arrangements of Eupodoidea and Tydeoidea are not only identical to each other but also identical to that of the hypothesized arthropod ancestor, showing a high level of conservatism in the mitogenomic structure of these mite superfamilies. Our study illustrates the utility of gene arrangements for providing complementary information to nucleotide sequences with respect to inferring the evolutionary relationships of species within the order Trombidiformes. The mitogenome of H. destructor provides a valuable resource for further population genetic studies of this important agricultural pest. Given the co‐occurrence of closely related, morphologically similar Penthaleidae mites with H. destructor in the field, a complete mitogenome provides new opportunities to develop metabarcoding tools to study mite diversity in agro‐ecosystems. Moreover, the H. destructor mitogenome fills an important taxonomic gap that will facilitate further study of trombidiform mite evolution., We report the complete mitogenome sequence of the redlegged earth mite, Halotydeus destructor (Tucker). We used Bayesian phylogenetic analyses to contextualize the relationship of H. destructor with other trombidiform mites. Phylogenies were inferred from protein‐coding and rRNA genes using nucleotide sequences and a novel characterization of gene order arrangements.

Genomic data provide valuable insights into pest management issues such as resistance evolution, historical patterns of pest invasions and ongoing population dynamics. We assembled the first reference genome for the redlegged earth mite,Halotydeus destructor(Tucker, 1925), to investigate adaptation to pesticide pressures and demography in its invasive Australian range using whole-genome pool-seq data from regionally distributed populations. Our reference genome comprises 132 autosomal contigs, with a total length of 48.90 Mb. We observed a large complex ofacegenes, which has presumably evolved from a long history of organophosphate selection inH. destructorand may contribute toward organophosphate resistance through copy number variation, target-site mutations, and structural variants. In the putative ancestralH. destructor acegene, we identified three target-site mutations (G119S, A201S, and F331Y) segregating in organophosphate resistant populations. Additionally, we identified two newparasodium channel gene mutations (L925I and F1020Y) that may contribute to pyrethroid resistance. Regional structuring observed in population genomic analyses indicates that gene flow inH. destructordoes not homogenise populations across large geographic distances. However, our demographic analyses were equivocal on the magnitude of gene flow; the short invasion history ofH. destructormakes it difficult to distinguish scenarios of complete isolation vs. ongoing migration. Nonetheless, we identified clear signatures of reduced genetic diversity and smaller inferred effective population sizes in eastern vs. western populations, which is consistent with the stepping-stone invasion pathway of this pest in Australia. These new insights will inform development of diagnostic genetic markers of resistance, further investigation into the multifaceted organophosphate resistance mechanism, and predictive modelling of resistance evolution and spread.

Some leafmining fly species are pests of agricultural and ornamental plants but they also include many species with little economic importance. The taxonomy of leafmining flies is often challenging because of putative cryptic species. Following new outbreaks of Liriomyza (Diptera:Agromyzidae) in Australia, we here characterize 13 dipteran leafminer species collected from Australia based on cytochrome c oxidase subunit 1 (COI) DNA barcodes, and we compare these with overseas data. We confirm barcodes of nine species from the Agromyzidae (Liriomyza sativae, L. huidobrensis, L. trifolii, L. bryoniae, L. chinensis, L. brassicae, L. chenopodii, Phytomyza plantaginis and P. syngenesiae) and one species from the Drosophilidae (Scaptomyza flava); we describe new haplotypes for some of these species. Furthermore, we provide the first DNA barcodes for two species (Cerodontha milleri and Phytoliriomyza praecellens) from the Agromyzidae and one species (Scaptomyza australis) from the Drosophilidae. These findings provide a baseline for DNA-based identification of pest Liriomyza incursions spreading across the Australian east coast in relation to other species already present in Australia.

Chemical strategies to manage pest populations that have evolved pesticide resistance can involve killing resistant individuals by using higher rates of the same pesticide or applying alternative pesticides for which resistance does not exist. However, the dilemma is that alternative pesticides available for many pest species are limited, while higher pesticide rates may lead to the evolution of higher resistance levels. Here, both strategies are tested in a resistant population of the redlegged earth mite, Halotydeus destructor, which contained resistance against two groups of chemicals: synthetic pyrethroids and organophosphates. Resistant mites were introduced into exclusion field plots, which were then treated with pyrethroid, organophosphate or alternative chemicals for 2 years at a low pressure (one spray at the registered field rate per year) or a high pressure (two sprays at the registered field rate per year). A single pyrethroid application suppressed mite numbers, but pyrethroid-resistant allele (kdr) frequencies quickly rose from ∼50% to nearly 100%. Thereafter, pyrethroid chemicals lost effectiveness. However, kdr frequencies declined across mite generations when pyrethroids were not used, regardless of other treatments. Organophosphates continued to suppress mite populations under both high and low pressures, irrespective of kdr allele frequencies, and laboratory bioassays showed no increase in organophosphate resistance levels. One of the alternative chemicals, diafenthiuron, applied once per year over two years, successfully suppressed mite numbers, whereas other treatments did not control mites. These findings demonstrate that different strategies are required to manage H. destructor with pyrethroid resistance and organophosphate resistance.

BACKGROUND: The global pest spotted winged drosophila (Drosophila suzukii) continues to have a significant economic impact on fruit production in areas where it is established, in addition to newly invaded ranges. Management activities spanning national biosecurity responses to farm-scale pest control are limited by the inability to predict the timing and severity of seasonal outbreaks of D. suzukii and its climatic drivers. RESULTS: Here, we compiled and analysed data on international seasonal abundances for D. suzukii under different climates, crop types and management contexts to improve the predictability of seasonal population dynamics. In relating seasonal abundances to environmental predictors, specifically temperature, we found strong negative effects of exposure to high and low temperatures during the preceding month. Unlike most regional studies on D. suzukii phenology that focus on temperature in the physiological development range, we show that thermal extremes better explain seasonal population fluctuations. CONCLUSION: Although trap catches remain an indirect measure of infestations and must be interpreted carefully in terms of crop risk, our results should support monitoring programmes through enhanced knowledge of the climatic factors affecting D. suzukii population activity. The negative impact of high temperatures suggests that late-season management strategies focusing on manipulating crop microclimates to temperatures above 25 °C can reduce D. suzukii abundance. We show that early season abundance is modulated by climate, particularly the depth of cold extremes experienced in the preceding time interval. These associations may be further developed into early-season crop risk forecasts to support monitoring programs. © 2021 Society of Chemical Industry.

Herbicides are the largest category of pesticides used in global agriculture, which is reflected in the rate of increase in the number of unique cases of herbicide-resistant weed biotypes since the late 1950s. Recommended herbicide resistance management strategies and tactics have evolved over the past 50 years through cumulative research and experience and have been regularly reviewed. Nevertheless, new perspectives may be gained by viewing current recommended strategies through the lens of insecticide, fungicide, and antibiotic resistance management. What commonalities exist and what is the basis for disparate strategies? Although pesticide and antibiotic mixtures (or combinations) are generally more effective than rotations (or alternations) in mitigating or managing resistance, the latter strategy is often employed because of greater ease of implementation and other reasons. We conclude that there are more common than different strategies for mitigating or managing pesticide and antibiotic resistance. Overall, a reduction in selection pressure for resistance evolution through diverse multi-tactic management programmes, and disruption or mitigation of the dispersal or transmission of problematic genotypes are needed to sustain the longevity of current and future mode-of-action products for crop and human health protection. © 2021 Society of Chemical Industry. © 2021 Society of Chemical Industry.

Pyrethroid resistance in the redlegged earth mite, Halotydeus destructor (Tucker), is primarily attributed to a kdr (knockdown resistance) mutation in the parasodium channel gene. To assess fitness costs associated with this resistance, adult resistant and susceptible populations were mixed in different proportions in microcosm tubs and placed in a shade-house simulating field conditions. Three separate experiments were undertaken whereby parental mites were collected from the field and offspring were followed for two to three generations. The association between fitness costs and kdr-mediated resistance was investigated by examining differences in mite numbers and changes in resistant allele frequencies across generations. In two (of the three) experiments, the population fitness measure of mites was significantly lower in microcosms containing a higher proportion of resistant individuals compared with treatments containing susceptible mites. No differences in mite fitness were observed between treatments in the third experiment; in this instance, the starting proportion of individuals homozygous for the resistant mutation was much lower (~40%) than in the other experiments (>90%). In all three experiments, a decrease in the resistant allele frequency across mite generations was observed. These findings indicate a potential deleterious pleiotropic effect of the kdr mutation on the fitness of H. destructor and have implications for resistance management strategies aimed at this important agricultural pest. Further experiments investigating fitness costs directly in the field are warranted.

BACKGROUND: The redlegged earth mite, Halotydeus destructor Tucker, is a destructive and economically important pest of winter grain crops and pastures in Australia. It is largely controlled by pesticides, but this mite has evolved resistance to pyrethroid and organophosphate chemicals. A national Resistance Management Strategy has been developed for pro-active management to delay further resistance evolution, though its success is reliant on a detailed understanding of the incidence, patterns of spread, current distribution and the nature of resistance in the field. Here, we report on a long-term resistance surveillance program undertaken between 2006 and 2019 informed by resistance risk forecasting. RESULTS: By mapping the Australian distribution of resistance through time, we show that resistance is present across three Australian states and covers more than 3000 km. This current range includes a recently identified population exhibiting organophosphate resistance representing the most easterly location of resistance in H. destructor. Using field history information, we identify associations for the first time between crop management practices employed by farmers and the presence of pyrethroid resistance. Management strategies that could minimise the risk of further resistance include limiting local spread of resistance through farm hygiene practices, crop rotations and reducing pesticide usage. CONCLUSION: This study highlights the challenges of resistance in H. destructor but also indicates how quantitative resistance risk analysis can be developed to target field surveillance and delay further resistance. The management strategies highlighted in this study can help maintain the effectiveness of control options but will depend on farmer engagement and adoption. This article is protected by copyright. All rights reserved.

Estimating parasitoid abundance in the field can be difficult, even more so when attempting to quantify parasitism rates and the ecosystem service of biological control that parasitoids can provide. To understand how 'field observed' parasitism rates (in-field mummy counts) of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) translate to 'laboratory observed' parasitism rates (laboratory-reared parasitoid counts), field work was undertaken in Australian canola fields, over the winter growing season.Overall, laboratory observed parasitism was on average 2.4 times higher than field observed parasitism, with rates an average of four-fold higher in fields from South Australia. Total field observed and laboratory observed parasitism rates (OPRs) of M. persicae varied considerably across regions, but less so among fields within regions. As crop growth stage progressed, the incidence of field observed mummies increased. The incidence of total parasitoids reared also increased with crop growth stage, averaging 3.4% during flowering and reaching 14.4% during podding/senescing. Although there was a greater diversity of reared parasitoid species at later crop growth stages, the laboratory OPR was unaffected by parasitoid species. Diaeretiella rapae was the most commonly reared parasitoid, increasing in absolute abundance with crop growth stage.These findings indicate that field mummy counts alone do not provide a clear representation of parasitism within canola fields. © 2022 The Authors. Pest Management Science published by John WileySons Ltd on behalf of Society of Chemical Industry.

BACKGROUND The European earwig, Forficula auricularia (L.) (Dermaptera: Forficulidae), is regarded as an important beneficial in many orchard environments but has the potential to be a plant pest in other systems, including to grain crops. Due to its agricultural importance, the lifecycle of F. auricularia has been widely studied in North America and Europe. However, much less is known in the southern hemisphere, including Australia where F. auricularia has been present for over 170 years. RESULTS To elucidate the lifecycle of F. auricularia, we monitored five sites in grain‐growing areas of southern Australia using two different trap types. Adults were found year‐round, but most prevalent from late‐spring to mid‐winter. First instars were typically found from mid to late winter. Second, third and fourth instars occurred from winter through to late spring. The seasonal development of F. auricularia in Australia may be much earlier than observed in comparable North American studies. Degree day modelling highlights variation in development times across the active season for F. auricularia across our sites. CONCLUSION Forficula auricularia is well adapted to the Australian grain growing environments. The timing of egg hatching aligns closely with crop emergence, juveniles then develop alongside the crop, and adult development occurs by harvest time in late spring. These findings are important given that many of these crops (canola, lucerne, pulses) are vulnerable to attack by F. auricularia during emergence and development. They also suggest a phenotypic capacity of this species to adapt different phenology after introduction into a novel environment. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., The lifecycle of Forficula auricularia in grain crops is presented. We found that the Australian populations of Forficula auricularia may develop much earlier than observed in comparable North American studies. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Predicting biological invasions remains a challenge to applied ecologists and limits pre-emptive management of biosecurity threats. In the last decade, spotted-wing drosophila Drosophila suzukii has emerged as an internationally significant agricultural pest as it rapidly spread across Europe and the Americas. However, the underlying drivers of its global invasion remain unstudied, while countries like Australia, presently free from D. suzukii, require robust estimates of spread and establishment potential to aid development of effective preparedness strategies. Here, we analysed the ecoclimatic and human-mediated drivers of the global invasion of D. suzukii to understand historical spread patterns and improve forecasts of future spread potential. Using a modular approach, climate-driven population dynamics were linked in space via dispersal processes to simulate spread at continental scales. Combined with biological parameters measured in laboratory studies, the spread model was parameterized and validated on international spread data. Model accuracy was high and was able to predict 83% of regional presence–absence through time in the United States and, without further model fitting, 78% of the variation in the Europe incursion. Omitting human-assisted spread from the model reduced predictability by over 20%, highlighting the large anthropogenic influence in this modern biological invasion. Economic activity (GDP) rather than human population density was more strongly associated with human-mediated spread. Simulations predicted that eastern Australian coastal regions, particularly those near major cities with high economic activity, will result in the fastest spread of D. suzukii. Synthesis and applications. Incursions of Drosophila suzukii into Australia will have significant consequences for horticultural industries with the predicted speed of spread making eradication programs extremely difficult. However, the identified areas of significant fruit production, and high environmental suitability and economic activity will form a logical means for prioritizing industry preparedness. In light of our findings, a key component of preparedness strategies will be the ability of fruit producers to rapidly transition to effective management of D. suzukii.

The preference of herbivores for different host plants can be modulated by plant ontogeny. In agricultural pest management, this has implications for sowing dates and pest monitoring. In the last 20 years, the European earwig (Forficula auricularia), a cosmopolitan pest, has been increasingly implicated in damage to grain crops in Australia. Among these, rapeseed, Brassica napus, appears especially at risk, but little information on F. auricularia as a grain pest is available. We tested the susceptibility of seven grain crops commonly grown in Australia to infestation by F. auricularia using closed microcosm experiments, exposing plant seedlings at two early growth stages to four different life stages of F. auricularia. Lucerne and rapeseed were shown to be the most vulnerable crops, and younger seedlings experienced significantly more damage than older seedlings across all crop types. Fourth instar F. auricularia were found to cause greater feeding damage than younger or older earwigs, while adults collected in winter generally caused more damage than those collected in summer. Surprisingly, even second instar F. auricularia caused greater damage than summer adults. This variation could reflect the ontogenetically dynamic nutritional needs of earwigs. Recent studies of F. auricularia's life cycle in southern Australia indicate that these damaging life stages have some overlap with sowing dates of the crops tested here, exposing their vulnerable seedling stage to infestation. The phenology of F. auricularia in southern Australia therefore partly drives its ability to act as a pest. Future monitoring will likely need to track the distribution of F. auricularia life stages in order to effectively mitigate risks to vulnerable crops.

The Russian wheat aphid, Diuraphis noxia (Mordvilko ex Kurdjumov), is one of the world's most economically important pests of grain crops and has been recorded from at least 140 grass species within Poaceae. It has rapidly dispersed from its native origin of Central Asia into most major grain-producing regions of the world including Africa, Asia, Europe, the Middle East, North America and South America. Diuraphis noxia was first found in Australia in a wheat crop in the mid-north of South Australia in May 2016. Since then, D. noxia has been recorded throughout grain-growing regions of South Australia, Victoria, New South Wales and Tasmania. The distribution will continue to expand, with climatic suitability modelling suggesting D. noxia can persist in all key grain regions, including large parts of Western Australia and Queensland. Australian populations of D. noxia appear to be anholocyclic, with no sexual stages being observed. The aphids can reproduce year round as long as host plants are available. Australian farmers have generally adopted prophylactic insecticide seed treatments and/or foliar sprays to manage D. noxia. Research is required to fully understand yield impacts, host preferences and host plant resistance associated with D. noxia. Cultural control through managing alternate host plants over summer, agronomic crop management, biological control and developments in host plant resistance should provide considerable future benefits.

Quantifying how chemical tolerance of pest arthropods varies with temperature is important for understanding the outcomes of chemical control, for measuring and monitoring resistance, and for predicting how pesticide resistance will evolve under future climate change. We studied the redlegged earth mite, Halotydeus destructor (Tucker), a winter-active invasive agricultural pest in Australia. Using a replicated block experiment, we tested the effect of different thermal conditions on the expression of chemical tolerance to a pyrethroid and two organophosphates. Our chemical bioassays were conducted on two redlegged earth mite populations: one possessed organophosphate resistance, whilst the other was susceptible to pesticides. Mites were first acclimated at cool (4 °C) and warm (14 °C) conditions and then exposed to pesticides in both cool (11 °C) and warm (18 °C) test conditions.Warm test conditions generally reduced chemical tolerance to all pesticides relative to cool test conditions. Median lethal dose (LDOur data provides context for prior theoretical work demonstrating climatically constrained pesticide resistances in Australian redlegged earth mites. Estimates of temperature dependent toxicity measured in this study may be useful in parameterizing models of redlegged earth mite control under an increasingly warm and more variable climate. © 2022 The Authors. Pest Management Science published by John WileySons Ltd on behalf of Society of Chemical Industry.

Liriomyza sativae, the vegetable leafminer, is a serious agricultural pest originally from the Americas which has now colonized all continents except Antarctica. In 2015, L. sativae arrived on the Australian mainland and established on the Cape York Peninsula in the northeast of the country. Here, we assessed genetic variation in L. sativae based on genome-wide single nucleotide polymorphisms (SNPs) generated by double-digest restriction-site associated DNA sequencing (ddRAD-seq) to uncover the potential origin(s) of this pest in Australia and contribute to reconstructing its global invasion history. Our principal component analyses (PCA) results suggested that Australian mainland populations were genetically close to populations from the Torres Strait and had connections to Bali and Papua New Guinea (PNG), whereas populations from Asia and Africa were more distantly related. Hawaii was genetically distinct from populations from Asia, Africa and Australia. Co-ancestry analyses pointed to signals of gene flow from the Torres Strait into the Australian mainland, while Indonesia/PNG were the likely sources of the initial invasion into the Torres Strait. Admixture analyses further revealed that L. sativae from the Torres Strait had genetic diversity originating from multiple sources, which has now spread to the Australian mainland. The L. sativae lineages from Asia/Africa appear closely related and may share co-ancestry. Isolation by distance (IBD) was found at a broad global scale, but not within small regions, suggesting human-mediated factors contribute to the local spread of this pest. Overall, our findings highlight the challenges in quarantine measures aimed at restricting the distribution of this global pest.

The green peach aphid, Myzus persicae, is a highly damaging, globally distributed crop pest that has evolved multiple resistance to numerous insecticides. It is thus imperative that insecticides that are not strongly compromised by pre-existing resistance are carefully managed to maximise their effective life span. Sulfoxaflor is a sulfoximine insecticide that retains efficacy against M. persicae clones that exhibit resistance to older insecticides. In the current study we monitored the efficacy of sulfoxaflor against M. persicae populations collected in Western Australia, following reports of control failures in this region. We identified clones with low (4-23-fold across multiple independent bioassay experiments), but significant, levels of resistance to sulfoxaflor compared with a reference susceptible clone. Furthermore, we demonstrate that sulfoxaflor resistance can persist after many months of culturing in the laboratory in the absence of insecticide exposure. Resistance was not conferred by known mechanisms of resistance to neonicotinoid insecticides, that act on the same target-site as sulfoxaflor, i.e. the R81T mutation or overexpresssion of the P450 gene CYP6CY3. Rather, transcriptome profiling of multiple resistant and susceptible clones identified the P450 CYP380C40 and the UDP-glucuronosyltransferase UGT344P2 as highly overexpressed (21-76-fold and 6-33-fold respectively) in the resistant clones. Transgenic expression of these genes demonstrated that they confer, low, but significant, levels of resistance to sulfoxaflor in vivo. Taken together, our data reveal the presence of low-level resistance to sulfoxaflor in M. persicae populations in Australia and uncover two novel mechanisms conferring resistance to this compound. The findings and tools generated in this study provide a platform for the development of strategies that aim to slow, prevent or overcome the evolution of more potent resistance to sulfoxaflor.

The aphid Myzus persicae is a destructive agricultural pest that displays an exceptional ability to develop resistance to both natural and synthetic insecticides. To investigate the evolution of resistance in this species we generated a chromosome-scale genome assembly and living panel of >110 fully sequenced globally sampled clonal lines. Our analyses reveal a remarkable diversity of resistance mutations segregating in global populations of M. persicae. We show that the emergence and spread of these mechanisms is influenced by host–plant associations, uncovering the widespread co‐option of a host-plant adaptation that also offers resistance against synthetic insecticides. We identify both the repeated evolution of independent resistance mutations at the same locus, and multiple instances of the evolution of novel resistance mechanisms against key insecticides. Our findings provide fundamental insights into the genomic responses of global insect populations to strong selective forces, and hold practical relevance for the control of pests and parasites., Singh, Bass and colleagues generate new genomic resources for the aphid crop pest, Myzus persicae, comprising a chromosome-scale genome assembly and resequenced genomes of >100 globally sampled clonal lines. Using this dataset, they uncover both mechanisms underpinning the evolution of insecticide resistance and ecological factors that influence its emergence and spread.

The Russian wheat aphid (Diuraphis noxia [Kurdjumov, Hemiptera: Aphididae], RWA) was first detected in Australia in 2016 and is threatening an annual cereal industry valued at nearly 10 billion AUD per annum. Considerable uncertainty surrounds the economic risk of D. noxia to Australian cereals, which limits cost-effective farm management decisions. Through a series of inoculated and non-inoculated field trials in 2018 and 2019 in south-eastern Australia, we generated a range of D. noxia pressure metrics under different growing conditions for barley, wheat, and durum wheat. Relative yield loss was best explained by the ‘percentage of tillers with D. noxia’ (%TwRWA) with 0.28% yield loss per percent of tillers with D. noxia, which is significantly lower than 0.46–0.48% for susceptible winter wheat varieties in dryland conditions in the United States. Highest infestation levels were typically reached around GS40–50. To develop an action threshold, we calculated the rate of increase in the %TwRWA through time at 0.021% per day per %TwRWA (with little variation across sites). This allowed prediction of the expected maximum %TwRWA based on observations post tillering (GS30) and the expected duration before GS50 is reached. For earlier growth stages (