Land-use intensification and climate change have strong filtering effects on arthropod communities. Intensification increases landscape homogeneity and field-scale disturbance while extreme weather events are increasing with climate change. To disentangle their impacts, we analyzed predatory arthropod abundance and diversity across microhabitats (canopy, ground) and diet breadth (specialist, generalist, omnivore) in 58 sorghum fields in Uruguay over two years. Using a trait-based framework and Hierarchical Modelling of Species Communities, we found that double cropping negatively affected predator communities, reducing canopy predator abundance and ground predator species richness, especially ground omnivores. Larger fields decreased the proportion of canopy specialists in the community, and landscape homogeneity increased the proportion of ground omnivores. Extreme weather mainly affected ground predators, with species richness and abundance decreasing with high rainfall variability. The proportion of ground specialists decreased with both variable rainfall and more hot days. Omnivorous and generalist ground predators were more resilient to climatic stress and canopy predator abundance increased under heat extremes. Our findings suggest that land-use intensification exerts stronger negative effects on predator communities than extreme weather, though the latter can further reduce functional diversity. To enhance predator community resilience and support biological control, management strategies should prioritize reducing disturbances, such as double-cropping, and creating refuges within fields to protect against climatic extremes.

Effects of tillage in arable fields on taxonomic and functional responses of beneficial above- and below-ground arthropod communities are poorly understood. We assessed arthropod communities in 30 conventionally managed crop fields in south-western Sweden before and after autumn tillage. Treatments consisted of three levels of tillage intensity: inversion tillage, reduced tillage (non-inversion) and no tillage (direct seeding). Reduced tillage and no tillage are considered conservation tillage practices. All fields were sown with winter cereals in autumn 2019, followed by winter oilseed rape sown in late summer 2020. Tillage occurred between cereal harvest and the sowing of winter oilseed rape. We measured soil mesofauna density, and density, taxonomic, compositional and functional diversity of ground-dwelling predators. Inversion tillage decreased densities of above- and below-ground beneficial arthropods. Conservation tillage resulted in higher species richness and lower community turnover following disturbance. Community compositional shifts following inversion tillage were characterised by lower community weighted mean (CWM) body size and reduced densities of carabids overwintering as imago in autumn, and higher spider CWM body size in spring, compared with conservation tillage treatments. Inversion tillage reduced spider density and richness throughout the following growing season, while soil mesofauna densities, carabid taxonomic diversity and functional composition recovered by spring. Synthesis and applications: Responses to tillage were taxon-specific and likely depended on life-stage and the dependency on structural habitat complexity. Management should balance trade-offs between retaining local communities, meeting the needs of multiple taxa, and accounting for taxonomic and functional richness over time.

Arthropod predators and pests overwinter in arable fields, but little is known about predator and pest overwintering under contrasting tillage intensities. Further, the contribution of within-field overwintering predator communities to the overall ground dwelling community is understudied. We sampled arthropod predators (carabids, staphylinids and spiders) and pests overwintering in arable fields, and estimated the activity densities of overall ground dwelling predator communities from early spring until harvest 2021. We sampled 29 conventionally managed crop fields managed using no till (direct drill), reduced tillage (non-inversion) or inversion tillage between harvesting winter cereals and sowing winter oilseed rape in 2020. No till management resulted in higher species diversity of overwintering predators, compared with inversion tillage. Tillage effects on density of overwintering predators and pests depended on sampling time. Predator and pest emergence were higher under inversion tillage compared with no till early in the season. During mid and late season, predator emergence was higher under reduced tillage compared with no till and inversion tillage. Tillage had no effects on species richness but affected community composition (beta-diversity) of the overwintering predator communities. Overwintering and overall ground dwelling predator communities were distinctly different in early season and homogenised as the crop-growing season progressed. The high average density of predators emerging per m2 of arable soil within the fields, 108 carabids, 604 staphylinids and 56 spiders, emphasises the need to adapt arable management in order to support arthropod overwintering in crop fields for enhanced biological pest regulation.

Landscape ecologists have long suggested that pest abundances increase in simplified, monoculture landscapes. However, tests of this theory often fail to predict pest population sizes in real-world agricultural fields. These failures may arise not only from variation in pest ecology, but also from the widespread use of categorical land-use maps that do not adequately characterize habitat-availability for pests. We used 1163 field-year observations of Lygus hesperus (Western Tarnished Plant Bug) densities in California cotton fields to determine whether integrating remotely-sensed metrics of vegetation productivity and phenology into pest models could improve pest abundance analysis and prediction. Because L. hesperus often overwinters in non-crop vegetation, we predicted that pest abundances would peak on farms surrounded by more non-crop vegetation, especially when the non-crop vegetation is initially productive but then dries down early in the year, causing the pest to disperse into cotton fields. We found that the effect of non-crop habitat on pest densities varied across latitudes, with a positive relationship in the north and a negative one in the south. Aligning with our hypotheses, models predicted that L. hesperus densities were 35 times higher on farms surrounded by high versus low productivity non-crop vegetation (EVI area 350 vs. 50) and 2.8 times higher when dormancy occurred earlier versus later in the year (May 15 vs. June 30). Despite these strong and significant effects, we found that integrating these remote-sensing variables into land-use models only marginally improved pest density predictions in cotton compared to models with categorical land cover metrics alone. Together, our work suggests that the remote sensing variables analyzed here can advance our understanding of pest ecology, but not yet substantively increase the accuracy of pest abundance predictions.

Population cycles have been observed in mammals as well as insects, but consistent population cycling has rarely been documented in agroecosystems and never for a beetle. We analysed the long-term population patterns of the cabbage stem flea beetle Psylliodes chrysocephala in winter oilseed rape over 50 years. Psylliodes chrysocephala larval density from 3045 winter oilseed rape fields in southern Sweden showed strong 8-year population cycles in regional mean density. Fluctuations in larval density were synchronous over time across five subregional populations. Subregional mean environmental variables explained 90.6% of the synchrony in P. chrysocephala populations at the 7-11 year time-scale. The number of days below -10°C showed strong anti-phase coherence with larval densities in the 7-11 year time-scale, such that more cold days resulted in low larval densities. High levels of the North Atlantic Oscillation weather system are coherent and anti-phase with cold weather in Scania, Sweden. At the field-scale, later crop planting date and more cold winter days were associated with decreased overwintering larval density. Warmer autumn temperatures, resulting in greater larval accumulated degree days early in the season, increased overwintering larval density. Despite variation in environmental conditions and crop management, 8-year cycles persisted for cabbage stem flea beetle throughout the 50 years of data collection. Moran effects, influenced by the North Atlantic Oscillation weather patterns, are the primary drivers of this cycle and synchronicity. Insect pest data collected in commercial agriculture fields is an abundant source of long-term data. We show that an agricultural pest can have the same periodic population cycles observed in perennial and unmanaged ecosystems. This unexpected finding has implications for sustainable pest management in agriculture and shows the value of long-term pest monitoring projects as an additional source of time-series data to untangle the drivers of population cycles.

Slugs are important agricultural pests causing yearly yield losses. However, parasitizing helminths potentially could affect the size of the slug population. Here, a survey of terrestrial slug-parasitic helminths (nematodes and trematodes) was conducted for the first time in Sweden. In total, 268 terrestrial slugs were collected from 27 agricultural field edges in three seasons over 2020 and 2021 and dissected for presence of helminth parasites. Slugs belonging to the genus Arion were molecularly identified by mitochondrial DNA cytochrome c oxidase subunit I (COI) while parasites were identified using ribosomal RNA (18S). Overall, 13% of the collected slugs had helminth parasites and the likelihood of a slug being parasitized was highest in autumn. Slugs identified as Arion vulgaris were more likely to be parasitized than native slug species. The prevalence of nematodes and trematodes were similar; the dominant species found were Alloionema appendiculatum and Brachylaima thompsoni, respectively. This is the first record of the presence of these two species in Sweden.

Oilseed rape (OSR; Brassica napus) is a globally important crop which is increasingly under pressure from pests, pathogens and weeds. We investigated the potential of achieving multifunctional crop protection benefits by intercropping oilseed rape with legumes. A field experiment was conducted in which winter oilseed rape was intercropped with the annual frost sensitive legumes berseem clover (Trifolium alexandrinum) or spring faba bean (Vicia faba), or with the winter grain legumes winter faba bean or winter peas (Pisum sativum). We tracked damage to winter oilseed rape by autumn and spring pests (slugs and insects), pathogens, weed biomass, as well as oilseed rape and intercrop yield in each treatment. Intercropping treatments resulted in pest damage that was equivalent or lower than in oilseed rape alone. Follow up field and lab assessments for the frost sensitive legume intercrops provided evidence for a reduction in autumn pest damage to OSR. Each legume intercrop had its own benefits and drawbacks in relation to pest, pathogen and weed suppression, suggesting that the plant species selected for intercropping with oilseed rape should be based on the pests, pathogens and weeds of greatest concern locally to achieve relevant multifunctional benefits. Our study provides a framework for further experiments in which the multifunctional effects of intercropping on pests, pathogens and weeds can be quantified.

Agricultural production has intensified over the last century both across increasingly homogenized landscapes and at the field level. This study analyzes the effects of land-use intensity at both landscape and local scales on the main insect pests, predators and yield of grain sorghum as a summer crop in Uruguay. It represents one of very few landscape studies focused on a reduced intensity production system other than organic agriculture and adds information from an under-studied subtropical region. Piecewise structural equation models were used to compare the direct and indirect effects of intensification at landscape scales and more sustainable practices at a local scale on densities of Spodoptera frugiperda (fall armyworm) and Rhopalosiphum maidis (corn leaf aphid), coccinellid abundance and yield over a two-year period in sorghum fields in western Uruguay. Greater landscape intensity resulted in increased S. frugiperda densities. Lower intensity crop-grazing rotation production systems reduced R. maidis densities compared to continuous cropping systems. Additionally, S. frugiperda and R. maidis interacted indirectly through apparent commensalism in continuous cropping systems, but not in crop-grazing rotational systems. Single cropping management resulted in lower S. frugiperda density, while insecticide use had no effect on pest or predator species. Our analysis affirms that agricultural intensification benefits herbivorous arthropod pests at the landscape scale, but that local management practices can mitigate some of these effects.

1. Generalist predators are important contributors to reliable conservation biological control. Indirect interactions between prey species that share a common generalist predator can influence both community dynamics and the efficacy of biological control.2. Laboratory cage experiments investigated the impact of the combined consumptive and non‐consumptive effects of predation by adult Hippodamia convergens as a shared predator on the population growth and relative abundance of Acyrthosiphon pisum and Aphis gossypii as prey species. Predation pressure and prey density were varied.3. At low predation pressure the indirect interaction between aphid species was asymmetrical with a proportionally greater negative impact of predation on A. gossypii than on A. pisum. At intermediate predation pressure, the indirect interaction became symmetrical. At high predation pressure and higher levels of prey density, it was asymmetrical with greater negative impact on A. pisum, often driven to local extinction while A. gossypii populations persisted.4. A linear mixed‐effects model including early population growth of both aphid species and predation pressure explained 96% and 92% of the variation in the population growth of A. pisum and A. gossypii, respectively, over an 8‐day period. The overall effect of shared predation on the indirect interaction between the two aphid species is best described as apparent commensalism, where A. pisum benefited from early population growth of A. gossypii, while A. gossypii was unaffected by early population growth of A. pisum. Considering these indirect interactions is important for conservation biological control efforts to be successful.

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To more effectively manage walnut husk fly Rhagoletis completa (Diptera: Tephritidae), in California walnut orchards, it is important to understand the factors that affect the timing of adult emergence. In the present study, we examine the effects of incubation temperature, pre-chill and chill durations, latitude, cultivar and size on the post-diapause development of R. completa puparia. The lower developmental threshold, upper developmental threshold and optimal temperature for puparial development are estimated to be 4, 34 and 26.6 degrees C, respectively. The thermal requirement for adult emergence after 120 days of chilling is estimated to be 2024 degree days. Percentage adult emergence declines at both higher and lower incubation temperatures. Chill duration at 5 degrees C for diapausing puparia has a nonlinear negative effect on the thermal requirement but no effect on percentage emergence. Insufficient chilling leads to poor synchronization of adult emergence. Greater pre-chill duration at room temperature increases the thermal requirement and slightly decreased percentage emergence. Latitude has a negative effect on the thermal requirement. Puparia from northern California black walnut (Juglans hindsii) have a slightly greater thermal requirement than puparia from cultivated walnut (Julgans regia). There is no significant difference in puparial fresh weight or mean thermal requirement between males and females, although the positive correlation between thermal requirement and puparial fresh weight is stronger for females than males. The effects of temperature and other environmental factors on the post-diapause development of R. completa are discussed in relation to observations from other Rhagoletis species.

A phenology model of the walnut husk fly, Rhagoletis completa Cresson, was developed to more accurately predict the timing of the flight period and optimize management decisions. A data set of 153 orchard years in which adults were trapped throughout the season was used for the development and validation of this model. Data from California Irrigation Management Information System (CIMIS) weather stations were used to match orchard-year datasets with historical climatic data on degree-day (DD) accumulation, winter chill, and winter rainfall. A cumulative Weibull distribution was used to model the relationship between cumulative trap catch and DD accumulation for R. completa in California. The model was used to predict thermal requirements for the start (5% cumulative trap catch) and mid-point (50% cumulative trap catch) of the flight period, which were 1,670 and 2,179 DDs, respectively. The prediction for 50% cumulative trap catch of R. completa in California was much higher than the thermal requirement estimated in Oregon previously (1,751 DDs). Linear mixed effects models were used to evaluate other environmental and orchard-specific factors which could explain the large variation between predicted and observed thermal requirements for both the start and mid-point of the flight period. Latitude, walnut cultivar leaf-out time, orchard age and year, as a continuous variable, all contributed significantly to explain deviations from the predictions of the DD model for individual orchard years. Such factors can be used both to adjust predicted thermal requirements for these two specific and informative stages of the flight period, and to provide a basis for ecological and evolutionary hypotheses.