Microbial technologies are increasingly adopted to improve sustainable agriculture amid escalating economic, regulatory, and ecological pressures, yet few, if any, are supported by mechanistic understanding and are translated to products with demonstrated real-world performance and adoption. Pink-pigmented facultative methylotrophs (PPFMs) are known to promote plant growth and enhance pathogen resistance, but their impact on insect defense remains largely unexplored. Here we report on a PPFM species, Methylorubrum extorquens strain NLS0042, developed as TS201, a U.S. EPA–registered bioinsecticide that mitigates maize pest damage and improves yield. Across seven years (2016–2022) of field trials at 22 U.S. Midwest locations, TS201 increased maize yield by 220 kg/ha under moderate to high pressure of corn rootworms, the most destructive insect pest complex of maize in North America. Additionally, TS201 improved root architecture and reduced plant lodging. Large-scale on-farm evaluations across 81 sites in eight U.S. states (2023–2024) validated its agronomic benefit under diverse production conditions. Transcriptomic and volatile metabolite analyses revealed that TS201 induces anthranilate biosynthesis and accumulation of methyl anthranilate, a volatile compound that repels western corn rootworm larvae. Insect choice assays demonstrated significant larval avoidance of TS201-treated roots and confirmed the repellent effect of methyl anthranilate on corn rootworm larvae. These findings demonstrate that TS201 primes maize defense through multiple modes of action, offering a novel and effective microbial strategy to enhance crop resilience and support sustainable pest management.

Short-stature corn is approximately 60 cm shorter than conventional corn at maturity and is expected to soon be commercially available in the United States. One advantage of short-stature corn is lodging resistance, which should help facilitate its adoption by producers. However, knowledge gaps exist concerning how insect pests interact with short-stature corn. Western corn rootworm, Diabrotica virgifera virgifera LeConte, and European corn borer, Ostrinia nubilalis Hübner, are important pests of corn in the United States. To manage these pests, transgenic corn producing insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) is commonly planted. Blended refuges, where non-Bt and Bt plants are interspersed within a field, are a method of insect resistance management for Bt corn. However, past research has found that larval movement between Bt and non-Bt plants can reduce the effectiveness of non-Bt refuges in delaying Bt resistance. The primary goal of this work was to understand whether the effectiveness of a non-Bt blended refuge to delay resistance would be similar between tall corn and short-stature corn. We conducted a field study to evaluate larval survival and movement patterns between Bt and non-Bt corn. The experimental design simulated a blended refuge in order to understand whether patterns of pest movement and survival were similar between tall- and short-stature corn. We found larval movement and survival for both pests on short-stature corn largely resembled the effects on tall corn, and therefore, current resistance management strategies should be applicable for short-stature corn.

The western corn rootworm (WCR) and northern corn rootworm (NCR) are the two major belowground insect pests of corn in the U.S. Corn Belt. These species coexist in the same habitat, where their larvae feed on corn roots, increasing the risk of lodging and yield loss. Understanding larval competition between WCR and NCR is crucial for effective insect resistance management and integrated pest management. To assess interspecific larval competition between WCR and NCR, two independent greenhouse trials were conducted. We infested non-Bt corn plants with varying egg ratios of diapause and non-diapause populations of both species and counted the number of adults of each species recovered from each plant. Results showed that WCR consistently exhibited higher emergence rates than NCR, regardless of the initial egg infestation ratio. The observed ratio of NCR to WCR in both diapause and non-diapause groups was significantly lower than expected, suggesting that WCR is more competitive than NCR. The competitive dominance of WCR, coupled with climate warming, may facilitate its northward expansion across the U.S. This could potentially affect local NCR populations and further spread Bt and rotation resistance. Such changes could exacerbate pest management challenges in corn production systems. Integrating knowledge of corn rootworm competition, biology, resistance development, and climate change will be critical for developing informed management strategies to mitigate corn rootworm damage in agroecosystems effectively.

Deploying semiochemicals in pest management is challenging for pollinator-dependent crops because floral-based attractants can divert bees and other pollinators. Cucurbit crops, for example, are highly dependent on pollination and their primary pests, Acalymma vittatum (F.) (striped cucumber beetle, StCB) and Acalymma trivitatum (Mannerheim) (western striped cucumber beetle, WStCB), are strongly attracted to the scent of cucurbit blossoms. To identify a more pollinator-friendly semiochemical lure for StCBs, we conducted a 2-year field experiment across 4 US states (IN, MD, VA, CA) that evaluated pest responses to: (i) a cucurbit floral mimic (TIC), (ii) indole, a single component of TIC; and (iii) vittatalactone, an aggregation pheromone of StCB. These compounds were tested both individually and in combination to test for non-additivity. We also assessed responses from 2 other co-occurring pests-Diabrotica undecimpunctata howardi Barber (spotted cucumber beetle, SpCB), Diabrotica virgifera virgifera LeConte (western cornrootworm, WCR)-and pollinators (Apis mellifera L., honey bees; Eucera and Lasioglossum). We found that vittatalactone, but not TIC, was a strong and consistent attractant of Acalymma species (StCB, WStCB), whereas the reverse pattern was observed for Diabrotica species (SpCB, WCR). As expected, TIC-but not indole or vittatalactone-attracted pollinators. Pest trap catch was almost always highest when vittatalactone was combined with either indole or TIC, and this increase was synergistic in 33% of cases. These data suggest that combining indole with vittatalactone creates a potent pest attractant that does not attract bees, making it a pollinator-friendly lure.

The western corn rootworm (Diabrotica virgifera virgifera LeConte) remains one of the most damaging pests of maize across Europe, including Romania. Reliable integrated pest management relies on monitoring systems capable of capturing adult flight activity under field conditions. This study presents a comparative field evaluation of three monitoring approaches: Virgiwit yellow sticky panels (YSP), pheromone-based CSALOMON® KLP+ traps, and the automated iScout® digital monitoring system. Monitoring was conducted at weekly intervals over an eight-week period (20 July–15 September 2025) in four maize fields in western Romania. Capture data were analyzed descriptively to assess relative trap performance and to explore associations with selected meteorological variables. KLP+ traps consistently recorded the highest numbers of adults, while YSP traps reproduced the main seasonal flight patterns. The iScout® system captured fewer individuals but provided continuous temporal information on adult activity. Correlation analyses indicated generally weak and inconsistent relationships between trap captures and short-term weather variables, reflecting the limitations imposed by weekly manual sampling and site-specific variability. Overall, the results highlight the complementary strengths and limitations of manual and automated monitoring tools and support their exploratory use for characterizing seasonal flight activity and temporal population patterns of Diabrotica virgifera virgifera under field conditions. Further multi-year and device-specific validation is required before automated systems can be fully integrated into operational pest management frameworks.

Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a serious pest of maize (Zea mays L.) in the United States. Because western corn rootworm larvae live in the soil, conducting an on-plant bioassay to screen novel management tools can be challenging. This study aimed to identify growth media for a greenhouse bioassay system suitable for studying interactions between western corn rootworm larvae and maize plants. We assessed the effects of growth medium on the growth of maize plants and on the survival and development of western corn rootworm larvae. Additionally, we characterized how larval density affected rootworm survival in the bioassay system. Plants grew well in soil collected from an agricultural field; however, this bioassay environment also resulted in poor survival of western corn rootworm larvae. By contrast, larval survival was greatest when plants grew in vermiculite, but this medium tended to produce the lowest values for metrics of plant growth. In general, a potting medium was conducive to both higher levels of larval survival and plant growth metrics. These results suggest that use of a potting medium or a mixture of soil collected from the field with other amendments, such as potting medium, could provide an environment conducive to both the growth of maize plants and the survival of rootworm larvae. This bioassay approach offers a novel bioassay system, which may potentially be applied to screen insecticides, microbial biopesticides, and plant-incorporated protectants.

The suspension of neonicotinoid-based seed treatments in 2025 in Romania has renewed concern regarding the population resurgence of the western corn rootworm (Diabrotica virgifera virgifera LeConte), one of the most destructive pests of maize. This study, conducted at the Agricultural Research and Development Station (ARDS) Livada, evaluates the short-term consequences of eliminating neonicotinoid insecticides on maize root damage, adult density, and lodging incidence. Data from prior experiments (2011) and field observations in 2025 were analyzed to assess pest dynamics under varying climatic and agronomic conditions. Results showed that treatments with neonicotinoids such as clothianidin and imidacloprid (e.g., Poncho 600 FS, Nuprid AL 600 FS) significantly reduced larval populations (up to −34 %) and minimized plant lodging (<1 %). In contrast, the 2025 observations revealed renewed plant lodging (up to 3–4 %) and increased signs of root damage, likely associated with mild winter temperatures and the absence of chemical seed protection. Although differences among green manure types and fertilization treatments were statistically insignificant, these factors showed potential for integration into ecological control strategies. The findings emphasize the need for integrated pest management (IPM) approaches that combine crop rotation, soil amendment, biological control, and resistant hybrids to mitigate the expected resurgence of D. v. virgifera populations following the withdrawal of neonicotinoids.

BackgroundEntomopathogenic nematodes of the genus Heterorhabditis establish a symbiotic association with Photorhabdus bacteria. Together, they colonize and rapidly kill insects, making them important biological control agents against agricultural pests. Improving their biocontrol traits by engineering resistance to plant secondary metabolites (benzoxazinoids) in Photorhabdus symbiotic bacteria through experimental evolution has been shown to increase their lethality towards benzoxazinoid-defended larvae of the western corn rootworm, a serious crop pest of maize, and it is therefore a promising approach to develop more efficient biocontrol agents to manage this pest. To enhance our understanding of the genetic bases of benzoxazinoid resistance in Photorhabdus bacteria, we conducted an experimental evolution experiment with a phylogenetically diverse collection of Photorhabdus strains from different geographic origins. We cultured 27 different strains in medium containing 6-methoxy-2-benzoxazolinone (MBOA), a highly active benzoxazinoid breakdown product, for 35 24 h-cycles to select for benzoxazinoid-resistant strains. Then, we carried out genome-wide sequence comparisons to uncover the genetic alterations associated with benzoxazinoid resistance. Lastly, we evaluated the resistance of the newly isolated resistant Photorhabdus strains to eight additional bioactive compounds, including 2-benzoxazolinone (BOA), nicotine, caffeine, 6-chloroacetyl-2-benzoxazolinone (CABOA), digitoxin, fenitrothion, ampicillin, and kanamycin.ResultsWe found that benzoxazinoid resistance evolves rapidly in Photorhabdus in a strain-specific manner. Across the different Photorhabdus strains, a total of nineteen nonsynonymous point mutations, two stop codon gains, and one frameshift were associated with higher benzoxazinoid resistance. The different genetic alterations were polygenic and occurred in genes coding for the EnvZ/OmpR two-component regulatory system, the different subunits of the DNA-directed RNA polymerase, and the AcrABZ-TolC multidrug efflux pump. Apart from increasing MBOA resistance, the different mutations were also associated with cross-resistance to 2-benzoxazolinone (BOA), nicotine, caffeine, and 6-chloroacetyl-2-benzoxazolinone (CABOA) and with collateral sensitivity to fenitrothion, ampicillin, and kanamycin. Targeted mutagenesis will provide a deeper mechanistic understanding, including the relative contribution of the different mutation types.ConclusionsOur study reveals several genomic features that are associated with resistance to xenobiotics in this important group of biological control agents and enhances the availability of molecular tools to develop better biological control agents, which is essential for more sustainable and ecologically friendly agricultural practices.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12864-025-12067-x.

Pantoea ananatis was recently described as the causative agent of late-season decline, a new bacterial disease first observed affecting field corn plants, in the Texas Panhandle. The rapid spread of the disease throughout the region and the patchy distribution of symptomatic plants in affected fields, as well as routine observations of edge effects, in which plants with severe symptoms are observed on the edges of affected fields, led us to hypothesize that vectors might be involved in the dissemination of the disease pathogen. In this study, we investigated the western corn rootworm (Diabrotica virgifera virgifera LeConte) and southern corn rootworm (Diabrotica undecimpunctata howardi Barber) for any naturally occurring association with P. ananatis and potential to acquire and transmit the bacterial pathogen. Additionally, we investigated the transgenic corn encoding insecticidal Bacillus thuringiensis proteins (Bt) pyramided with RNAi interference anti-rootworm technology for its potential to protect against any larval role in the transmission of the pathogen through their feeding activities on corn roots. We successfully recovered naturally occurring P. ananatis from samples of both rootworm species collected from corn plants in the field. Following acquisition assays, the acquired pathogen was successfully recovered from previously P. ananatis-free adult rootworms, their eggs, as well as first-instar larvae, suggesting an affinity of the bacteria to establish an endosymbiotic and transovarial association with both rootworm species. Additionally, the transgenic Bt corn with RNAi anti-rootworm technology was ineffective in preventing the transmission of the pathogen by the infected larvae. Findings from this study confirm a vector role in the transmission of the disease pathogen.

This study investigated the dynamics of corn pest populations in organic and conventional cropping systems over a three-year corn–soybean–corn rotation (2022 to 2024), conducted in Bihor County, Romania. The experiment was carried out on two farms with similar pedoclimatic conditions (cambic chernozem, pH 6.9, 775 mm annual rainfall), where corn hybrids were grown under identical agronomic conditions, with three replicate plots per treatment. Adult populations of both specific (<em>Rhopalosiphum padi</em>, <em>Ostrinia nubilalis</em>, <em>Helicoverpa armigera</em>, <em>Diabrotica virgifera</em>) and non-specific pests (<em>Phyllotreta atra</em>, <em>Macrosteles </em>spp., <em>Agriotes </em>spp.) were monitored using standardized trap-based sampling. The objectives are to quantify pest pressure across systems and crops and evaluate the influence of soybean as a preceding crop on pest persistence in corn. For corn in 2022, specific pest abundance averaged 1,825.75±131.36 in organic plots vs. 625.25±45.42 in conventional ones (F = 212.84, <em>p</em> < 0.001, Cohen’s d = 11.91). Non-specific pests reached 1,501.33±126.54 in organic corn vs. 834.33±47.60 in conventional (F = 73.02, <em>p</em> = 0.001). In 2024, total pest pressure in organic corn rose to 5,279.67±512.06, compared to 1,683.33±42.22 (F = 146.98, <em>p</em> < 0.001). Pest levels decreased moderately across the organic rotation, suggesting a partial suppressive effect of soybean, absent in conventional plots. Relative abundance of key species exceeded 25 to 30%, indicating a high risk of damage in the absence of intervention. These results have practical implications for integrated pest management (IPM): organic systems require enhanced monitoring and biological control strategies, while soybean’s role in pest carryover should inform rotation planning.

Diabrotica virgifera virgifera Le Conte, 1868 (Coleoptera: Chrysomelidae), known as the western corn rootworm, is one of the most important alien insect pests affecting maize crops globally. It causes significant economic losses by feeding on the roots, which affects plant stability and nutrient absorption, as well as by attacking essential aerial organs (leaves, silk, pollen). Since its accidental introduction into Europe, the species has expanded its range across maize-growing regions, raising concerns about future distribution under climate change. This study aimed to estimate the risk of pest establishment across Europe over three future time frames (2034, 2054, 2074) based on geographic coordinates, climate data, and maize distribution. Spatial simulations were performed in QGIS using national centroid datasets, risk classification criteria, and temperature anomaly maps derived from Copernicus and ECA&D databases for 1992-2024. The results indicate consistently high risk in southern and southeastern regions, with projected expansion toward central and western areas by 2074. Risk zones showed clear spatial aggregation and directional spread correlated with warming trends and maize availability. The pest's high reproductive potential, thermal tolerance, and capacity for human-assisted dispersal further support these predictions. The model emphasizes the need for expanded surveillance in at-risk zones and targeted policies in areas where D. v. virgifera has not yet established. Future work should refine spatial predictions using field validation, genetic monitoring, and dispersal modeling. The results contribute to anticipatory pest management planning and can support sustainable maize production across changing agroclimatic zones in Europe.

Abstract Although research on below‐ground multitrophic interactions has increased, comparative studies examining how root herbivores influence the foraging behaviour of different natural enemies—especially generalist predators—remains limited. Parasitoids are thought to depend on more host‐specific cues that reveal not only location but also quality of hosts, while predators utilize more general signals and are less dependent on prey quality. Thus, we expected that parasitoids would prefer hosts on plants without below‐ground damage, and parasitization on those plants would be higher. In contrast, we expected that a generalist predator would not distinguish between hosts on either plant. We investigated these questions using a focal system of corn aphids ( Rhopalosiphum maidis ), the convergent lady beetle ( Hippodamia convergens ), and the parasitoid Aphidius colemani on maize ( Zea mays ). Specifically, we determined how root feeding by Western corn rootworm (WCR, Diabrotica virgifera virgifera ) larvae altered aphid population growth, consumption by predators, and parasitism rates. We also analysed how the presence of WCR and aphids altered above‐ground maize volatile blends and natural enemy preference 24 h and 1 week after aphid herbivory. Feeding by WCR larvae reduced aphid population size by 39% after 2 weeks. In contrast to our predictions, A. colemani produced an equal number of mummies per female between the two treatments, while lady beetles consumed more aphids on control plants. However, A. colemani preferred plants with aphids alone over control plants after 24 h of aphid feeding but did not distinguish between other pairwise comparisons, while H. convergens did not distinguish between different herbivory treatments at 24 h or 1 week in choice assays. Analysis of above‐ground volatiles demonstrated that at both time points, the combination of above‐ and below‐ground herbivory explained more of the variation in volatile blends than either above‐ or below‐ground herbivory alone. Furthermore, the interaction of above‐ and below‐ground herbivory reduced volatile richness compared to single herbivory at 24 h. Our results suggest that below‐ground feeding can inhibit parasitoid ability to identify plants with hosts in a critical early search window, potentially weakening trophic linkages. Additionally, over biologically relevant timescales of herbivore population growth, we see a shift in the identity of natural enemies displaying preferences for specific herbivory treatments: In contrast to parasitoids, the presence of below‐ground herbivores enhanced lady beetle host location, but only after a week of aphid feeding. Read the free Plain Language Summary for this article on the Journal blog.

Crops genetically engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have revolutionized pest management, but their benefits have been reduced by evolution of practical resistance in at least 31 cases. To delay evolution of resistance, farmers have shifted from crops producing one Bt protein to crops called pyramids that produce two or more Bt proteins or other traits targeting each pest. Here, we focus on resistance to transgenic corn pyramids in the western corn rootworm (Diabrotica virgifera virgifera) and northern corn rootworm (Diabrotica barberi), which cost farmers in the United States $2 billion yearly in yield losses. We analyzed 998 relevant data values for 2005 to 2023 from 12 published field studies. The results support the hypothesis that rootworm resistance to Bt proteins Cry3Bb and Gpp34/Tpp35Ab reduces the efficacy of pyramids that produce one or both of these proteins and an RNA interference trait (DvSnf7) targeting rootworms, despite no apparent strong cross-resistance between the Bt proteins and DvSnf7. The reduced efficacy of pyramids producing Bt proteins and DvSnf7 entails increased root injury and emergence of adult beetles. Efficacy of DvSnf7 was substantially lower for reducing root injury than emergence. Because root injury decreases yield, the increased root injury has immediate practical consequences. More sustainable control may be achieved by deploying pyramids with traits that are each highly effective against rootworms, increasing the abundance of host plants that do not target rootworms, and combining transgenic corn with crop rotation and other control tactics in integrated pest management programs.

Western corn rootworm, Diabrotica virgifera virgifera, is one of the most economically important crop pests in the world with estimates of damage and control costing over $1 billion USD annually. Yet despite an abundance of research devoted to studying rootworm biology in the central Corn Belt of the United States, information on key aspects of their thermal biology is still lacking. In this study, we quantified thermal metrics of western corn rootworm populations from across their range in the United States: we measured critical thermal limits, knock-down resistance, and chill coma recovery for male and female rootworm from 13 laboratory colonies that were collected across 1985km at locations that varied by up to 5.7°C in mean annual temperature. We further use these data to test a model from thermal ecology-the thermal adaptation hypothesis-which posits that (1) thermal limits track environmental temperatures and (2) more thermally variable environments support organisms with broader thermal ranges. In doing so, we found that thermal traits varied across populations. However, only heat tolerance traits (critical thermal maximum and knock-down resistance) tracked historical averages of mean annual temperature. Rootworm originating from more thermally variable environments did not exhibit broader thermal ranges. While theory often predicts cold tolerance should track environmental temperatures, our results suggest this pattern may disappear if organisms are reared in the laboratory for multiple generations and instead a legacy effect may exist for heat tolerance that is rarely reported.

The western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte is an important insect pest of maize (Zea mays L.) in the midwestern United States of America (USA) and has evolved resistance to maize hybrids producing toxins from the bacterium Bacillus thuringiensis Berliner (Bt). This study was conducted in a landscape with a high proportion of continuous maize (maize planted ≥ two consecutive years) during 2021-2022 in northeast Nebraska, USA to increase our understanding of adult WCR activity in first-year maize and the introduction of Bt resistance by WCR immigrants. Pherocon AM unbaited sticky traps were placed at ear height in first-year maize fields and replaced weekly during adult WCR activity periods to determine density and gender of captured adults. Maize and WCR phenological interactions plus gender-specific behaviors appeared to be key determinants of WCR activity in first-year maize. Comparison of adult emergence and root injury in first- and second-year maize fields confirmed that crop rotation reduces a WCR population to near-zero. Field collections of adults were made from first-year and some adjacent continuous maize fields to estimate Bt susceptibility with Bt bioassays of F1 progeny. Similar resistance levels were observed in WCR collections from first-year and many adjacent continuous maize fields. Aggregate study results suggest adjacent maize fields were a major contributor of WCR immigrants. Significant variation in WCR immigration/ colonization and associated Bt resistance levels were observed in first-year maize, so scouting of first-year maize fields is recommended to match appropriate WCR management approaches to relative risk of injury in second-year maize.

A coherent understanding of adult western corn rootworm (Diabrotica virgifera virgifera) movement ecology has remained elusive because of conflicting evidence of short- and long-distance lifetime dispersal, a type of dilemma called Reid's Paradox. Attempts to resolve this paradox using population genetics strategies have been hindered by the lack of gene flow-genetic drift equilibrium in much of North America related to this species' recent range expansion out of the Great Plains across the Corn Belt. We addressed this challenge by studying a longer-established population in northeastern Colorado and western Kansas, where D. v. virgifera has been resident for >175 yr. We assessed population differentiation using 2,036 single-nucleotide polymorphism markers to obtain indirect estimates of dispersal distances. Significant isolation by distance and pairwise FST estimates across 14 locations suggest these populations are at or near gene flow-genetic drift equilibrium. Low FST values and shallow isolation-by-distance slopes suggest gene flow over longer distances (280 km) than supported by many direct measures of dispersal distance, another type of dilemma known as Slatkin's Paradox. Indeed, based on estimates of adult population density and Wright's neighborhood at each location, median estimated lifetime dispersal of ~87% of adults was only 174 m. Together, our genetic evidence and findings from earlier studies suggest that D. v. virgifera populations consist of 2 behavioral phenotypes, migrants that engage in long-distance dispersal and residents that disperse only locally by diffusion. The resulting bimodal dispersal distribution resolves both Reid's and Slatkin's paradoxes.

Many invasive species undergo a significant reduction in genetic diversity, i.e. a genetic bottleneck, in the early stages of invasion. However, this reduction does not necessarily prevent them from achieving considerable ecological success and becoming highly efficient colonizers. Here we investigated the purge hypothesis, which suggests that demographic bottlenecks may facilitate conditions (e.g., increased homozygosity and inbreeding) under which natural selection can purge deleterious mutations, thereby reducing genetic load. We used a transcriptome-based exome capture protocol to identify thousands of SNPs in coding regions of native and invasive populations of two highly successful invasive insect species, the western corn rootworm (Chrysomelidae: Diabrotica virgifera virgifera ) and the harlequin ladybird (Coccinelidae: Harmonia axyridis ). We categorized and polarized SNPs to investigate changes in genetic load between invasive populations and their sources. Our results differed between species. In D. virgifera virgifera , although there was a general reduction in genetic diversity in invasive populations, including that associated with genetic load, we found no clear evidence for purging of genetic load, except marginally for highly deleterious mutations in one European population. Conversely, in H. axyridis , the reduction in genetic diversity was minimal, and we detected signs of genetic load fixation in invasive populations. These findings provide new insights into the evolution of genetic load during invasions, but do not offer a definitive answer to the purge hypothesis. Future research should include larger genomic datasets and a broader range of invasive species to further elucidate these dynamics.

Insect responses to warming temperatures are determined partly by their physiology, which is influenced by genetic factors and plasticity induced by past temperature exposure. The effect that prior high temperature exposure has on insect thermal tolerance is complex and depends on the degree of heat stress experienced; high heat exposure may allow for individuals to tolerate higher temperatures through hardening or may reduce an individual's capacity to withstand higher temperatures through accumulated heat stress. In this study, we assessed how short exposures to high temperatures and a laboratory colony's geographical origin affected the critical thermal maximum (CTmax) of western corn rootworm (Diabrotica virgifera virgifera LeConte), an economically important pest. Despite a wide latitudinal range of source populations, western corn rootworm colonies did not differ in their CTmax. Regardless of colony origin, we found that exposing western corn rootworm to higher temperatures resulted in lower CTmax, which suggests that heat stress accumulated. This study highlights how western corn rootworm experiences heat stress at temperatures near the temperatures they experience in the field, which may have important and currently unknown implications for its behavior.

This paper aimed to determine the attack caused by WCR (Diabrotica virgifera virgifera Le Conte) and its control by chemical treatments on soil and vegetation. The research was carried out in eastern Romania between 2023 and 2024, where two trials were conducted in the experimental field of the Agricultural Research and Development Station Secuieni-Neamt, where three granular insecticides applied to the soil against larvae and three chemical insecticides used on vegetation against adults were tested. Among the granular insecticides tested, the Force G (tefluthrin 15 g/kg) insecticide stood out with the best results, significantly reducing the number of larvae/plant (1 larva/plant) and, at the same time, the absence of the swan neck symptom was also recorded. Regarding insecticides applied to vegetation, the best results were obtained with the insecticide Inazuma (acetamiprid 100 g/kg + lambda-cyhalothrin 30 g/kg), which recorded a very good efficacy in combating adults of the species (95.4%). In conclusion, applying chemical treatments to soil and vegetation is necessary to control the attack by western corn rootworm (WCR).

Transgenic crops that produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) are grown worldwide to manage insect pests. Western corn rootworm is a serious pest of maize in the United States and is managed with Bt maize. In the United States, the commercial cultivation of a Bt crop requires an accompanying resistance-management strategy to delay the evolution of Bt resistance. One of the primary resistance-management strategies consists of non-Bt refuges along with a Bt crop that produces two Bt toxins (i.e., a pyramid) that kill the same pest species. This approach delays resistance because individuals with resistance to one toxin are killed by the second. However, if a pest species is resistant to one toxin in a pyramid, the effectiveness of a pyramid to delay resistance is compromised, potentially leading to the evolution of resistance to both toxins. Here, we apply a meta-analysis to demonstrate the sequential evolution of resistance by western corn rootworm to Bt maize producing Cry3Bb1 followed by resistance to Gpp34/Tpp35Ab1 maize, with resistance to each Bt toxin increasing in a linear manner over time. Additionally, we show that Bt-resistant western corn rootworm imposed substantial feeding injury, in the field, to maize containing a pyramid of Gpp34/Tpp35Ab1 and Cry3Bb1. To minimize the risk of sequential evolution of resistance to multiple transgenic traits, an emphasis should be placed on developing transgenic pyramids not compromised by prior resistance, and in cases where resistance is already present, larger non-Bt refuges and more diversified pest-management approaches should be applied.