Warmer temperatures trigger insecticide-associated pest outbreaks.

BACKGROUND: Rising global temperatures are associated with emerging insect pests, reflecting earlier and longer insect activity, faster development, more generations per year and changing species' ranges. Insecticides are often the first tools available to manage these new threats. In the southeastern US, sweet potato whitefly (Bemisia tabaci) has recently become the major threat to vegetable production. We used data from a multi-year, regional whitefly monitoring network to search for climate, land use, and management correlates of whitefly activity. RESULTS: Strikingly, whiteflies were detected earlier and grew more abundant in landscapes with greater insecticide use, but only when temperatures were also relatively warm. Whitefly outbreaks in hotter conditions were not associated with specific active ingredients used to suppress whiteflies, which would be consistent with a regional disruption of biocontrol following sprays for other pests. In addition, peak whitefly detections occurred earlier in areas with more vegetable production, but later with more cotton production, consistent with whiteflies moving among crops. CONCLUSION: Altogether, our findings suggest possible links between warmer temperatures, more abundant pests, and frequent insecticide applications disrupting biological control, though this remains to be explicitly demonstrated. Climate-initiated pesticide treadmills of this type may become an increasingly common driver of emerging pest outbreaks as global change accelerates. © 2023 Society of Chemical Industry.

Prevalence and molecular characterization of Salmonella isolated from wild birds in fresh produce environments.

Wild birds pose a difficult food safety risk to manage because they can avoid traditional wildlife mitigation strategies, such as fences. Birds often use agricultural fields and structures as foraging and nesting areas, which can lead to defecation on crops and subsequent transfer of foodborne pathogens. To assess the food safety risk associated with these events, wild bird feces were collected from produce fields across the southeastern United States during the 2021 and 2022 growing seasons. In total 773 fecal samples were collected from 45 farms across Florida, Georgia, South Carolina, and Tennessee, and 2.1% (n = 16) of samples were Salmonella-positive. Importantly, 75% of Salmonella were isolated from moist feces, showing reduced Salmonella viability when feces dry out. 16S microbiome analysis showed that presence of culturable Salmonella in moist feces correlated to a higher proportion of the Enterobacteriaceae family. From the Salmonella-positive samples, 62.5% (10/16) contained multi-serovar Salmonella populations. Overall, 13 serovars were detected, including six most commonly attributed to human illness (Enteriditis, Newport, Typhimurium, Infantis, Saintpaul, and Muenchen). PCR screening identified an additional 59 Salmonella-positive fecal samples, which were distributed across moist (n = 44) and dried feces (n = 15). On-farm point counts and molecular identification from fecal samples identified 57 bird species, including for 10 Salmonella-positive fecal samples. Overall, there was a low prevalence of Salmonella in fecal samples, especially in dried feces, and we found no evidence of Salmonella transmission to proximal foliage or produce. Fecal samples collected in farms close together shared highly related isolates by whole genome sequencing and also had highly similar Salmonella populations with comparable relative frequencies of the same serovars, suggesting the birds acquired Salmonella from a common source.

Glucagon-like Peptide-1 Receptor Pathway Attenuates Platelet Activation in Aspirin-Exacerbated Respiratory Disease.

Platelets are key contributors to allergic asthma and aspirin-exacerbated respiratory disease (AERD), an asthma phenotype involving platelet activation and IL-33-dependent mast cell activation. Human platelets express the glucagon-like peptide-1 receptor (GLP-1R). GLP-1R agonists decrease lung IL-33 release and airway hyperresponsiveness in mouse asthma models. We hypothesized that GLP-1R agonists reduce platelet activation and downstream platelet-mediated airway inflammation in AERD. GLP-1R expression on murine platelets was assessed using flow cytometry. We tested the effect of the GLP-1R agonist liraglutide on lysine-aspirin (Lys-ASA)-induced changes in airway resistance, and platelet-derived mediator release in a murine AERD model. We conducted a prospective cohort study comparing the effect of pretreatment with liraglutide or vehicle on thromboxane receptor agonist-induced in vitro activation of platelets from patients with AERD and nonasthmatic controls. GLP-1R expression was higher on murine platelets than on leukocytes. A single dose of liraglutide inhibited Lys-ASA-induced increases in airway resistance and decreased markers of platelet activation and recruitment to the lung in AERD-like mice. Liraglutide attenuated thromboxane receptor agonist-induced activation as measured by CXCL7 release in plasma from patients with AERD and CD62P expression in platelets from both patients with AERD (n = 31) and nonasthmatic, healthy controls (n = 11). Liraglutide, a Food and Drug Administration-approved GLP-1R agonist for treatment of type 2 diabetes and obesity, attenuates in vivo platelet activation in an AERD murine model and in vitro activation in human platelets in patients with and without AERD. These data advance the GLP-1R axis as a new target for platelet-mediated inflammation warranting further study in asthma.

Omnivore diet composition alters parasite resistance and host condition.

Diet composition modulates animals' ability to resist parasites and recover from stress. Broader diet breadths enable omnivores to mount dynamic responses to parasite attack, but little is known about how plant/prey mixing might influence responses to infection. Using omnivorous deer mice (Peromyscus maniculatus) as a model, we examine how varying plant and prey concentrations in blended diets influence resistance and body condition following infestation by Rocky Mountain wood ticks (Dermacentor andersoni). In two repeated experiments, deer mice fed for 4 weeks on controlled diets that varied in proportions of seeds and insects were then challenged with 50 tick larvae in two sequential infestations. The numbers of ticks successfully feeding on mice declined by 25% and 66% after the first infestation (in the first and second experiments, respectively), reflecting a pattern of acquired resistance, and resistance was strongest when plant/prey ratios were more equally balanced in mouse diets, relative to seed-dominated diets. Diet also dramatically impacted the capacity of mice to cope with tick infestations. Mice fed insect-rich diets lost 15% of their body weight when parasitized by ticks, while mice fed seed-rich diets lost no weight at all. While mounting/maintaining an immune response may be energetically demanding, mice may compensate for parasitism with fat and carbohydrate-rich diets. Altogether, these results suggest that a diverse nutritional landscape may be key in enabling omnivores' resistance and resilience to infection and immune stressors in their environments.

Wind Speed and Landscape Context Mediate Campylobacter Risk among Poultry Reared in Open Environments.

Foodborne pathogens cause over 9 million illnesses in the United States each year, and Campylobacter from chickens is the largest contributor. Rearing poultry outdoors without the use of antibiotics is becoming an increasingly popular style of farming; however, little is understood about how environmental factors and farm management alter pathogen prevalence. Our survey of 27 farms in California, Oregon, Washington, and Idaho, USA, revealed a diversity of management practices used to rear poultry in the open environment. Here, we assess environmental and management factors that impact Campylobacter spp. prevalence in 962 individual chicken fecal samples from 62 flocks over a three-year period. We detected Campylobacter spp. in 250/962 (26.0%) of fecal samples screened, in 69.4% (43/62) of flocks, and on 85.2% (23/27) of farms. We found that Campylobacter spp. prevalence was predicted to increase in poultry on farms with higher average wind speeds in the seven days preceding sampling; on farms embedded in more agricultural landscapes; and in flocks typified by younger birds, more rotations, higher flock densities, and the production of broilers. Collectively, our results suggest that farms in areas with higher wind speeds and more surrounding agriculture face greater risk of Campylobacter spp. introduction into their flocks.

Past and recent farming degrades aquatic insect genetic diversity.

Recent declines in once-common species are triggering concern that an environmental crisis point has been reached. Yet, the lack of long abundance time series data for most species can make it difficult to attribute these changes to anthropogenic causes, and to separate them from normal cycles. Genetic diversity, on the other hand, is sensitive to past and recent environmental changes, and reflects a measure of a populations' potential to adapt to future stressors. Here, we consider whether patterns of genetic diversity among aquatic insects can be linked to historical and recent patterns of land use change. We collated mitochondrial cytochrome c oxidase subunit I (COI) variation for >700 aquatic insect species across the United States, where patterns of agricultural expansion and intensification have been documented since the 1800s. We found that genetic diversity was lowest in regions where cropland was historically (pre-1950) most extensive, suggesting a legacy of past environmental harm. Genetic diversity further declined where cropland has since expanded, even after accounting for climate and sampling effects. Notably though, genetic diversity also appeared to rebound where cropland has diminished. Our study suggests that genetic diversity at the community level can be a powerful tool to infer potential population declines and rebounds over longer time spans than is typically possible with ecological data. For the aquatic insects that we considered, patterns of land use many decades ago appear to have left long-lasting damage to genetic diversity that could threaten evolutionary responses to rapid global change.

A bipolar taxonomy of adult human brain sulcal morphology related to timing of fetal sulcation and trans-sulcal gene expression gradients.

We developed a computational pipeline (now provided as a resource) for measuring morphological similarity between cortical surface sulci to construct a sulcal phenotype network (SPN) from each magnetic resonance imaging (MRI) scan in an adult cohort (N=34,725; 45-82 years). Networks estimated from pairwise similarities of 40 sulci on 5 morphological metrics comprised two clusters of sulci, represented also by the bipolar distribution of sulci on a linear-to-complex dimension. Linear sulci were more heritable and typically located in unimodal cortex; complex sulci were less heritable and typically located in heteromodal cortex. Aligning these results with an independent fetal brain MRI cohort (N=228; 21-36 gestational weeks), we found that linear sulci formed earlier, and the earliest and latest-forming sulci had the least between-adult variation. Using high-resolution maps of cortical gene expression, we found that linear sulcation is mechanistically underpinned by trans-sulcal gene expression gradients enriched for developmental processes.

Diversity and Prevalence of Ectoparasites on Poultry from Open Environment Farms in the Western-United States of Washington, Idaho, Oregon, and California.

Open-environment poultry farms that allow chickens to forage outdoors are becoming increasingly common throughout the United States and Europe; however, there is little information regarding the diversity and prevalence of ectoparasites in these farming systems. Eight to 25 birds were captured and surveyed for ectoparasites on each of 17 farms across the states of Washington, Idaho, Oregon, and California. Among the farms sampled, six louse species (Phthiraptera: Ischnocera & Amblycera) and two parasitic mite species (Acari: Mesostigmata) were collected and identified: Goniodes gigas (Taschenberg, 1879; Phthiraptera: Menoponidae) on one farm, Menacathus cornutus (Schömmer, 1913; Phthiraptera: Menoponidae) on one farm, Menopon gallinae (Linnaeus, 1758; Phthiraptera: Menoponidae) on six farms, Lipeurus caponis (Linnaeus, 1758; Phthiraptera: Philopteridae) on five farms, Menacanthus stramineus (Nitzsch, 1818; Phthiraptera: Menoponidae) on nine farms, Goniocotes gallinae De Geer (Phthiraptera: Philopteridae) on 11 farms, Dermanyssus gallinae (De Geer, 1778; Mesostigmata: Dermanyssidae) on two farms, and Ornithonyssus sylviarum (Canestrini & Fanzago, 1877; Mesostigmata: Macronyssidae) on one farm. The diversity of ectoparasites on these open environment poultry farms highlights a need for additional research on ectoparasite prevalence and intensity in these poultry farming systems.

Opposing global change drivers counterbalance trends in breeding North American monarch butterflies.

Many insects are in clear decline, with monarch butterflies (Danaus plexippus) drawing particular attention as a flagship species. It is well documented that, among migratory populations, numbers of overwintering monarchs have been falling across several decades, but trends among breeding monarchs are less clear. Here, we compile >135,000 monarch observations between 1993 and 2018 from the North American Butterfly Association's annual butterfly count to examine spatiotemporal patterns and potential drivers of adult monarch relative abundance trends across the entire breeding range in eastern and western North America. While the data revealed declines at some sites, particularly the US Northeast and parts of the Midwest, numbers in other areas, notably the US Southeast and Northwest, were unchanged or increasing, yielding a slightly positive overall trend across the species range. Negative impacts of agricultural glyphosate use appeared to be counterbalanced by positive effects of annual temperature, particularly in the US Midwest. Overall, our results suggest that population growth in summer is compensating for losses during the winter and that changing environmental variables have offsetting effects on mortality and/or reproduction. We suggest that density-dependent reproductive compensation when lower numbers arrive each spring is currently able to maintain relatively stable breeding monarch numbers. However, we caution against complacency since accelerating climate change may bring growing threats. In addition, increases of summer monarchs in some regions, especially in California and in the south, may reflect replacement of migratory with resident populations. Nonetheless, it is perhaps reassuring that ubiquitous downward trends in summer monarch abundance are not evident.

Precipitation change accentuates or reverses temperature effects on aphid dispersal.

Global temperatures are generally increasing, and this is leading to a well documented advancement and extension of seasonal activity of many pest insects. Effects of changing precipitation have received less attention, but might be complex because rain and snow are increasing in some places but decreasing in others. This raises the possibility that altered precipitation could accentuate, or even reverse, the effects of rising temperatures on pest outbreaks. We used >592 K aphid suction-trap captures over 15 years, in the heavily farmed central USA, to examine how the activity of Aphis glycines (soybean aphid), Rhopalosiphum maidis (corn aphid), and Rhopalosiphum padi (bird cherry-oat aphid) changed with variation in both temperature and precipitation. Increasing precipitation caused late-season flight activity of A. glycines and early-season activity of R. padi to shift earlier, while increasing temperature did the same for early-season activity of A. glycines and R. maidis. In these cases, precipitation and temperature exhibited directionally similar, but independent, effects. However, precipitation sometimes mediated temperature effects in complex ways. At relatively low temperatures, greater precipitation generally caused late-season flights of R. maidis to occur earlier. However, this pattern was reversed at higher temperatures with precipitation delaying late-season activity. In contrast, greater precipitation delayed peak flights of R. padi at lower temperatures, but caused them to occur earlier at higher temperatures. So, in these two cases the interactive effects of precipitation on temperature were mirror images of one another. When projecting future aphid flight phenology, models that excluded precipitation covariates consistently underpredicted the degree of phenological advance for A. glycines and R. padi, and underpredicted the degree of phenological delay for R. maidis under expected future climates. Overall, we found broad evidence that changing patterns of aphid flight phenology could only be understood by considering both temperature and precipitation changes. In our study region, temperature and precipitation are expected to increase in tandem, but these correlations will be reversed elsewhere. This reinforces the need to include both main and interactive effects of precipitation and temperature when seeking to accurately predict how pest pressure will change with a changing climate.

Alternative prey mediate intraguild predation in the open field.

BACKGROUND: Generalist predators that kill and eat other natural enemies can weaken biological control. However, pest suppression can be disrupted even if actual intraguild predation is infrequent, if predators reduce their foraging to lower their risk of being killed. In turn, predator-predator interference might be frequent when few other prey are available, but less common when herbivorous and detritus-feeding prey are plentiful. We used molecular gut-content analysis to track consumption of the predatory bug Geocoris sp. by the larger intraguild predator Nabis sp., in organic and conventional potato (Solanum tuberosum) fields. RESULTS: We found that higher densities of both aphids and thrips, two common herbivores, correlated with higher probability of detecting intraguild predation. Perhaps, Nabis foraging for these herbivores also encountered and ate more Geocoris. Surprisingly, likelihood of intraguild predation was not strongly linked to densities of either Nabis or Geocoris, or farming system, suggesting a greater importance for prey than predator community structure. Intriguingly, we found evidence that Geocoris fed more often on the detritus-feeding fly Scaptomyza pallida with increasing predator evenness. This would be consistent with Geocoris shifting to greater foraging on the ground, where S. pallida would be relatively abundant, in the face of greater risk of intraguild predation. CONCLUSION: Overall, our findings suggest that while herbivorous prey may heighten intraguild predation of Geocoris in the foliage, detritivores might support a shift to safer foraging on the ground. This provides further evidence that prey abundance and diversity can act to either heighten or relax predator-predator interference, depending on prey species identity and predator behavior. © 2022 Society of Chemical Industry.

Prevalence Patterns for Enteric Parasites of Chickens Managed in Open Environments of the Western United States.

Growing demand for poultry meat and eggs labeled as organic, cage free, or pasture raised has increased the number of producers that manage chickens outdoors. In these open environments, there are likely diverse enteric parasites sustained by fecal-oral transmission or passage through intermediate invertebrate hosts (e.g., worms and insects) that chickens consume. Enteric parasites can reduce chicken health and productivity, but there are few published data describing the identities or prevalence of these parasites on farms that use open environments in the United States. We surveyed 27 poultry farms with open environments that were situated across a wide geographic range, including California, Oregon, Idaho, and Washington. These farms did not use anticoccidial drugs, coccidia vaccines, or parasiticides. Flock size, enclosure area, flock density, flock rotation frequency, and average flock age were highly correlated for all the farms in this study. We analyzed how enclosure size and flock rotations per year (which represented two axes of variation in management) correlated with prevalence of five observed parasite taxa at the farm level. Across all flocks, we detected by fecal flotation Eimeria spp. (95% flocks), Ascaridia galli (69%), Heterakis gallinarum (52%), Capillaria spp. (39%), Strongyloides avium (13%), tapeworm species (29%), Cryptosporidium spp. (3%), and Dispharynx nasuta (1%). Eighty-five percent of samples were coinfected with two or more parasite taxa. Sixty-seven percent of farms raised only layer chicken breeds, 4% raised only broiler breeds, and 30% raised both layer and broiler breeds. The average age of the broiler flocks was 11.0 wk (±1.1 SE), and flocks were moved 54.7 (±17.9) times annually to new locations in pastures (hereafter, "rotation"). Layer flocks averaged 84.9 (±7.67) wk of age and were moved less often on farms being rotated 20.0 (±6.05) times per year. Generalized linear mixed models indicated that for every 1 m2 increase in enclosure size, the odds of detecting Eimeria spp. increased by 0.03%. Furthermore, for every additional rotation per year, the odds of detecting A. galli decreased by 1.3%. For every additional rotation per year, the odds of detecting tapeworm species increased by 2.2%. We found no evidence that flock spatial management affected prevalence of the other parasites observed on the farms. Farming practices and parasite responses in these systems are highly varied, which makes it difficult to identify potential management interventions for reducing these infections.

Patrones de prevalencia de parásitos entéricos de pollos manejados en ambientes abiertos en el oeste de los Estados Unidos. La creciente demanda de carne de pollo y huevos etiquetados como orgánicos, sin jaula o criados en pastoreo ha aumentado el número de productores que manejan pollos al aire libre. En estos entornos abiertos, es probable que existan diversos parásitos entéricos que permanecen debido a la transmisión fecal-oral o por su paso a través de huéspedes invertebrados intermedios (por ejemplo, gusanos e insectos) que son consumidos por los pollos. Los parásitos entéricos pueden reducir la salud y la productividad de los pollos, pero existe poca información publicada que describa las identidades o la prevalencia de estos parásitos en granjas que utilizan entornos abiertos en los Estados Unidos. Se realizó una encuesta incluyendo 27 granjas avícolas con entornos abiertos que estaban situadas en un amplio rango geográfico, incluyendo California, Oregón, Idaho y Washington. Estas granjas no usaban medicamentos anticoccidiales, vacunas contra coccidias ni parasiticidas. El tamaño de la parvada, el área de pastoreo, la densidad de la parvada, la frecuencia de rotación de la parvada y la edad promedio de la parvada estuvieron altamente correlacionados para todas las granjas en este estudio. Se analizó cómo el tamaño del recinto y las rotaciones de parvadas por año (que representaban dos ejes de variación en el manejo) se correlacionaban con la prevalencia de cinco taxones de parásitos observados a nivel de granja. En todas las parvadas, se detectó por flotación fecal Eimeria spp. (95% de las parvadas), Ascaridia galli (69%), Heterakis gallinarum (52%), Capillaria spp. (39%), Strongyloides avium (13%), especies de nemátodos planos (29%), Cryptosporidium spp. (3%) y Dispharynx nasuta (1%). El ochenta y cinco por ciento de las muestras estaban coinfectadas con dos o más taxones de parásitos. El sesenta y siete por ciento de las granjas criaban solo razas de gallinas de postura, el 4% solo criaban razas de pollos de engorde y el 30% criaban razas de gallinas de postura y de pollos de engorde. La edad promedio de las parvadas de pollos de engorde fue de 11.0 semanas (±1.1 SE) y las parvadas se trasladaron 54.7 (±17.9) veces al año a nuevas ubicaciones en los pastos (en adelante, "rotación"). Las parvadas ponedoras promediaron 84.9 (± 7.67) semanas de edad y se trasladaron con menos frecuencia en granjas que se rotaron 20.0 (± 6.05) veces al año. Los modelos lineales mixtos generalizados indicaron que por cada aumento de un metro cuadrado en el tamaño del área de pastoreo, las probabilidades de detectar Eimeria spp. se incrementaron en un 0.03%. Además, por cada rotación adicional por año, las probabilidades de detectar A. galli disminuyeron en un 1.3%. Por cada rotación adicional por año, las probabilidades de detectar especies de tenia aumentaron en un 2.2%. No encontramos evidencia de que el manejo del espacio de la parvada afectara la prevalencia de los otros parásitos observados en las granjas. Las prácticas agrícolas y las respuestas de los parásitos en estos sistemas son muy variadas, lo que dificulta la identificación de posibles intervenciones de manejo para reducir estas infecciones.

A trait-based framework for predicting foodborne pathogen risk from wild birds.

Recent foodborne illness outbreaks have heightened pressures on growers to deter wildlife from farms, jeopardizing conservation efforts. However, it remains unclear which species, particularly birds, pose the greatest risk to food safety. Using >11,000 pathogen tests and 1565 bird surveys covering 139 bird species from across the western United States, we examined the importance of 11 traits in mediating wild bird risk to food safety. We tested whether traits associated with pathogen exposure (e.g., habitat associations, movement, and foraging strategy) and pace-of-life (clutch size and generation length) mediated foodborne pathogen prevalence and proclivities to enter farm fields and defecate on crops. Campylobacter spp. were the most prevalent enteric pathogen (8.0%), while Salmonella and Shiga-toxin producing Escherichia coli (STEC) were rare (0.46% and 0.22% prevalence, respectively). We found that several traits related to pathogen exposure predicted pathogen prevalence. Specifically, Campylobacter and STEC-associated virulence genes were more often detected in species associated with cattle feedlots and bird feeders, respectively. Campylobacter was also more prevalent in species that consumed plants and had longer generation lengths. We found that species associated with feedlots were more likely to enter fields and defecate on crops. Our results indicated that canopy-foraging insectivores were less likely to deposit foodborne pathogens on crops, suggesting growers may be able to promote pest-eating birds and birds of conservation concern (e.g., via nest boxes) without necessarily compromising food safety. As such, promoting insectivorous birds may represent a win-win-win for bird conservation, crop production, and food safety. Collectively, our results suggest that separating crop production from livestock farming may be the best way to lower food safety risks from birds. More broadly, our trait-based framework suggests a path forward for co-managing wildlife conservation and food safety risks in farmlands by providing a strategy for holistically evaluating the food safety risks of wild animals, including under-studied species.

Alternative prey and farming system mediate predation of Colorado potato beetles by generalists.

BACKGROUND: Biological control by generalist predators can be mediated by the abundance and biodiversity of alternative prey. When alternative prey draw predator attacks away from the control target, they can weaken pest suppression. In other cases, a diverse prey base can promote predator abundance and biodiversity, reduce predator-predator interference, and benefit biocontrol. Here, we used molecular gut-content analysis to assess how community composition altered predation of Colorado potato beetle (Leptinotarsa decemlineata (Say)) by Nabis sp. and Geocoris sp. Predators were collected from organic or conventional potato (Solanum tuberosum L.) fields, encouraging differences in arthropod community composition. RESULTS: In organic fields, Nabis predation of potato beetles decreased with increasing arthropod richness and predator abundance. This is consistent with Nabis predators switching to other prey species when available and with growing predator-predator interference. In conventional fields these patterns were reversed, however, with potato beetle predation by Nabis increasing with greater arthropod richness and predator abundance. For Geocoris, Colorado potato beetle predation was more frequent in organic than in conventional fields. However, Geocoris predation of beetles was less frequent in fields with higher abundance of the detritus-feeding fly Scaptomyza pallida Zetterstedt, or of all arthropods, consistent with predators choosing other prey when available. CONCLUSION: Alternative prey generally dampened predation of potato beetles, suggesting these pests were less-preferred prey. Nabis and Geocoris differed in which alternative prey were most disruptive to feeding on potato beetles, and in the effects of farm management on predation, consistent with the two predator species occupying complementary feeding niches. © 2021 Society of Chemical Industry.

Complex life histories predispose aphids to recent abundance declines.

Many animals change feeding habits as they progress through life stages, exploiting resources that vary in space and time. However, complex life histories may bring new risks if rapid environmental change disrupts the timing of these switches. Here, we use abundance times series for a diverse group of herbivorous insects, aphids, to search for trait and environmental characteristics associated with declines. Our meta dataset spanned three world regions and >300 aphid species, tracked at 75 individual sites for 10-50 years. Abundances were generally falling, with median changes of -8.3%, -5.6%, and -0.1% per year in the central USA, northwestern USA, and United Kingdom, respectively. Aphids that obligately alternated between host plants annually and those that were agricultural pests exhibited the steepest declines, relative to species able to persist on the same host plant year-round or those in natural areas. This suggests that host alternation might expose aphids to climate-induced phenology mismatches with one or more of their host plant species, with additional risks from exposure to insecticides and other management efforts. Warming temperatures through time were associated with milder aphid declines or even abundance increases, particularly at higher latitudes. Altogether, while a warming world appeared to benefit some aphid species in some places, most aphid species that had time-sensitive movements among multiple host plants seemed to face greater risk of decline. More generally, this suggests that recent human-induced rapid environmental change is rebalancing the risks and rewards associated with complex life histories.

Recent climate change is creating hotspots of butterfly increase and decline across North America.

Some insect populations are experiencing dramatic declines, endangering the crucial ecosystem services they provide. Yet, other populations appear robust, highlighting the need to better define patterns and underlying drivers of recent change in insect numbers. We examined abundance and biodiversity trends for North American butterflies using a unique citizen-science dataset that has recorded observations of over 8 million butterflies across 456 species, 503 sites, nine ecoregions, and 26 years. Butterflies are a biodiverse group of pollinators, herbivores, and prey, making them useful bellwethers of environmental change. We found great heterogeneity in butterfly species' abundance trends, aggregating near zero, but with a tendency toward decline. There was strong spatial clustering, however, into regions of increase, decrease, or relative stasis. Recent precipitation and temperature appeared to largely drive these patterns, with butterflies generally declining at increasingly dry and hot sites but increasing at relatively wet or cool sites. In contrast, landscape and butterfly trait predictors had little influence, though abundance trends were slightly more positive around urban areas. Consistent with varying responses by different species, no overall directional change in butterfly species richness or evenness was detected. Overall, a mosaic of butterfly decay and rebound hotspots appeared to largely reflect geographic variability in climate drivers. Ongoing controversy about insect declines might dissipate with a shift in focus to the causes of heterogeneous responses among taxa and sites, with climate change emerging as a key suspect when pollinator communities are broadly impacted.

Insect-plant relationships predict the speed of insecticide adaptation.

Herbivorous insects must circumvent the chemical defenses of their host plants and, in cropping systems, must also circumvent synthetic insecticides. The pre-adaptation hypothesis posits that when herbivorous insects evolve resistance to insecticides, they co-opt adaptations against host plant defenses. Despite its intuitive appeal, few predictions of this hypothesis have been tested systematically. Here, with survival analysis of more than 17,000 herbivore-insecticide interactions, we show that resistance evolution tends to be faster when herbivorous insect diets are broad (but not too broad) and when insecticides and plant defensive chemicals are similar (but not too similar). These general relations suggest a complex interplay between macro-evolutionary contingencies and contemporary population genetic processes, and provide a predictive framework to forecast which pest species are most likely to develop resistance to particular insecticide chemistries.

Selection for high levels of resistance to double-stranded RNA (dsRNA) in Colorado potato beetle (Leptinotarsa decemlineata Say) using non-transgenic foliar delivery.

Insecticidal double-stranded RNAs (dsRNAs) silence expression of vital genes by activating the RNA interference (RNAi) mechanism in insect cells. Despite high commercial interest in insecticidal dsRNA, information on resistance to dsRNA is scarce, particularly for dsRNA products with non-transgenic delivery (ex. foliar/topical application) nearing regulatory review. We report the development of the CEAS 300 population of Colorado potato beetle (Leptinotarsa decemlineata Say) (Coleoptera: Chrysomelidae) with > 11,100-fold resistance to a dsRNA targeting the V-ATPase subunit A gene after nine episodes of selection using non-transgenic delivery by foliar coating. Resistance was associated with lack of target gene down-regulation in CEAS 300 larvae and cross-resistance to another dsRNA target (COPI ß; Coatomer subunit beta). In contrast, CEAS 300 larvae showed very low (~ 4-fold) reduced susceptibility to the Cry3Aa insecticidal protein from Bacillus thuringiensis. Resistance to dsRNA in CEAS 300 is transmitted as an autosomal recessive trait and is polygenic. These data represent the first documented case of resistance in an insect pest with high pesticide resistance potential using dsRNA delivered through non-transgenic techniques. Information on the genetics of resistance and availability of dsRNA-resistant L. decemlineata guide the design of resistance management tools and allow research to identify resistance alleles and estimate resistance risks.