Grasshopper Populations Research Articles

Limited genetic variability and spatial population structure in grasshoppers between natural and metal-contaminated areas in Egypt.

Pollutants in an environment can have long-term implications for the species living there, resulting in local adaptations with implications for their genetic structure. Heavy metal pollutants infiltrate soils and groundwater, bioaccumulate in food webs, and negatively impact biota. In this study, we investigated the degree to which the genetic structure and variability of the slender green-winged grasshopper (Aiolopus thalassinus (Fabricius) (Orthoptera: Acrididae)) were impacted by heavy metal pollution and distance. We used the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) method to examine the genetic variability of populations in 3 heavy metal-polluted and 3 unpolluted locations across varying geographical distances in Egypt. The heavy metal concentrations of cadmium, copper, lead, and zinc were measured from the grasshopper tissue and soils. Sixty-nine unique and polymorphic bands were produced by 4 primers. Cluster and principal component analyses separated the populations inside and outside Cairo into 2 main branches, which were further divided into smaller branches corresponding to their geographical regions. We found no differences in the Shannon genetic diversity index between populations or with increasing heavy metal concentrations in either the soil or the grasshopper tissue. Our results showed a greater genetic variation among populations than between populations within the same location, indicating populations within locations were less differentiated than those between locations. The moderate correlation between genetic similarity and spatial distance suggests geographical isolation influenced grasshopper population differentiation. Based on the RAPD analysis, environmental pollutants and geographical distances impact the A. thalassinus population structure, potentially restricting gene flow between sites even at small spatial scales.

Integrating Statistical Models and Principal Component Analysis to Assess Grasshopper Distribution and Diversity in Matiari District, Sindh, Pakistan

This study offers a comprehensive analysis of grasshopper diversity and distribution across different sites of Matiari district, Sindh, Pakistan during 2021-22 by using advanced statistical and ecological methodologies. This research documented ten grasshopper species, revealing significant spatial and temporal patterns. Acrotylus humertianus and Aiolopus thalassinus were widely distributed, with Acrotylus humertianus showing peak abundance in Mooro Lakho, while Oedaleus rosesense demonstrated the highest overall density, reaching up to 20 individuals per site. Notably, species richness peaked at ten species in Hala during April 2022, indicating substantial temporal variability. Principal Component Analysis (PCA) highlighted distinct ecological niches, with Acrotylus humertianus scoring highly on PC1, suggesting it thrives under specific conditions. The Shannon-Wiener Index revealed Bhit Shah and Mooro Lakho as the most diverse sites, while Simpson's Diversity Index indicated lower diversity in Saedabad. The correlation analysis showed a moderate positive relationship between temperature and grasshopper density (r = 0.452), while humidity and soil type had minimal effects. Generalized Linear Model (GLM) analysis identified Locusta migratoria as the most effective model, with the lowest Deviance, AIC, and BIC values, reflecting its optimal fit. The study emphasizes the complex interplay between environmental factors and grasshopper populations, providing crucial insights for biodiversity conservation and ecological research. These results highlight the dynamic nature of grasshopper ecology and underscore the need for targeted conservation strategies based on environmental and temporal variations.

What is the risk of overcollecting for translocation? An opportunistic assessment of a wingless grasshopper

AbstractTranslocation is an increasingly used tool in conservation management, but there is a risk that source populations are overcollected. The risk depends critically on the detection probability and the source population size. We quantified this risk for a wingless grasshopper population in a patch of remnant habitat in suburban Melbourne that was condemned to be cleared for housing development. We collected ∼2000 grasshoppers in five samples spread over 1 month and used the results to estimate the initial population size (∼3400) with high confidence. Despite our perception of substantially depleting the population, we removed only an estimated 60%, and this relatively high fecundity (∼50 eggs per lifetime) annual species had recovered by the following year to near its original density. Wild‐to‐wild translocation is likely to be a low‐cost and effective strategy in the conservation of many invertebrates, and our findings highlight the feasibility of using natural source populations.

Grasshopper Species Composition and Severe Attack in the Semi-Arid Region of Rajasthan, India

Adequate knowledge is needed to know when grasshopper species abundance shifts and to follow severe outbreaks during microclimatic variations. Grasshoppers regularly cause enormous harm to a wide variety of crops and grazing lands; sometimes they show a potential attack on particular crops. A study was carried out in the southern region of Jaipur, Rajasthan, where 11 sites were weekly sampled to monitor grasshopper population dynamics, grasshopper densities, species composition, and vegetation loss from July 2021 to December 2022. A serious grasshopper attack was reported in 2021, with the highest grasshopper densities ranging from 5 to 17.5 per m2, whereas grasshopper densities dropped in 2022 from 4 to 14.5 per m2. In the survey area, the acridid grasshopper Hieroglyphus banian (Acrididae:Orthoptera) was reported as the most abundant species that was accountable for the majority of the crop damage in agricultural fields, followed by Spathosternum praciniferaum and Acrida turrita, respectively. The grasshopper population density was revealed to be significantly different in 2021 and 2022 (t = 1.568, df = 20, P = 2.086). Severe infestation was observed in all of the pearl millet fields and also in seasonal crops and vegetables, where H. banian caused 91% infestation, followed by S. praciniferaum with 7% and A. turrita with 2%, respectively. The study confirmed that climatic factors were significantly related to outbreaks and assessed their effect, which revealed a rare population in the summer season and peaked in the monsoon season. The finding provides important information for grasshopper risk forecasting, which is advantageous for preparing grasshopper risk maps, predicting the intensity of outbreaks, and developing an integrated pest management plan.

Insect-friendly harvest in hay meadows – Uncut refuges are of vital importance for conservation management

With ongoing industrialisation of farming practise, the area of species-rich temperate grasslands has strongly declined. Today, the remnants of these grasslands often suffer from habitat degradation due to unsuitable management. Here, we investigated the effects of the complete harvest process over the course of two harvest periods (mid-June and mid-August) on Orthoptera (hereinafter referred to as ‘grasshoppers’) in species-rich lowland hay meadows in southwestern Bavaria (Germany). We set up a randomised split-plot design including mown meadows (tractor-operated rotary-disc vs. double-bladed bar mower) and uncut refuges within grassland patches. Our study revealed that mower types did not differ in their effects on grasshopper mortality and that direct mortality through cutting was very low. By contrast, after mowing, on average 85–91 % of the individuals or biomass was lost by the end of the harvest process. However, in uncut refuges, grasshopper densities and biomass increased on average by 234–328 %. From the first to the second harvest period, an alignment in grasshopper densities and biomass between meadows and uncut refuges occurred. We explain the lack of direct cutting effects by the tall and dense vegetation of the hay meadows and, hence, the location of the grasshoppers far above the sphere of the mowers. Moreover, we assume that in particular emigration from the short and homogeneous meadows to uncut refuges or patch edges but also increased vertebrate predation were responsible for the severe grasshopper losses. Moreover, we hypothesise that grasshopper recolonization from the refuges to the meadows strongly contributed to the alignment in grasshopper densities from mid-June to mid-August. Hence, to protect abundant grasshopper populations in meadows in the long run, uncut refuges are of prime importance. Firstly, such refuges guarantee a continuity in (i) food resources, (ii) a balanced microclimate and (iii) shelter against predators and extreme weather events for the resident individuals. Consequently, they are not affected by any of the harvest-related losses. Secondly, they serve as an important refuge for the emigrants from the mown parts of the meadow.

Conservation genetics of the steno-endemic Chorthippus lacustris (Orthoptera: Acrididae)

Invertebrate populations are amongst the most widespread species, inhabiting a variety of habitats, however there is limited conservation effort due to the scarce knowledge on their population genetics. Here, we assess levels of genetic diversity and population structure of the Epirus dancing grasshopper (Chorthippus lacustris), a steno-endemic species, located in Northwest Greece, exhibiting a fragmented distribution. By utilizing two mitochondrial genes and amplified fragment length polymorphisms (AFLPs), we detected moderate to high levels of genetic diversity of the focal populations. Haplotype network analysis revealed the existence of private haplotypes with low genetic differentiation suggesting a sudden expansion of the species in the study area with subsequent isolations on suitable habitats. Despite the low genetic differentiation between the studied populations, our data further suggest a subtle subdivision of the populations and the existence of three genetic clusters. Implications for insect conservation: Our study is the first to provide insights into the population genetics of the steno-endemic grasshopper C. lacustris, highlighting the importance of preserving focal populations. The species inhabits areas subject to high changes in land use and fragmentation. We argue that the preservation and management of suitable habitats is essential for the viability of the grasshopper populations.

Identification of spatial distribution and drivers for grasshopper populations based on geographic detectors

Grasshoppers are important elements for supporting ecosystem services which make it important to understand their spatial distribution characteristics to reduce outbreaks, implement effective control while minimizing non-target impacts. The spatial software package Geographical Detector (GD) was used to rank the interaction and effects of 19 environmental factors on the distribution of grasshopper species were quantified in four types of steppes in Northwestern, China. Results showed that the distribution of the insect was mainly influenced by elevation (q = 0.44). Among the factor interactions, elevation ∩ average annual precipitation (q = 0.795) was the strongest, followed by elevation ∩ soil available nitrogen (q = 0.722). Temperate meadow steppe and temperate steppe were identified as the areas at greatest risk for grasshopper’s occurrence. This research shows that the Geographical Detector could be provided a useful tool to identify the driving forces for grasshopper distribution. Our research also offers a new method to more broadly understand the interactions between different drivers to explain the distribution of other insects.

Research on Transformer Fault Diagnosis Model Based on Improved GOA-SVM

A transformer fault diagnosis model based on the improved grasshopper optimization algorithm-optimized support vector machine (SVM) is proposed to improve the precision of transformer fault diagnosis and avoid the issues that the traditional grasshopper optimization algorithm (GOA) is prone to falling into local optimal solution and slow convergence. Firstly, the grasshopper population is initialized using the elite backward learning strategy to improve the initial population quality and search efficiency. Then, the Sigmoid function is introduced to improve the linear weight decreasing of the grasshopper algorithm into nonlinear weight decreasing to strike a balance between the algorithm’s capacity for both local and global exploration. Finally, the kernel function parameters and penalty coefficients of the SVM are optimized with the improved grasshopper optimization algorithm (IGOA) to establish a model based on dissolved gas analysis (DGA) in oil-based IGOA algorithm-optimized SVM for transformer fault diagnosis model and verify the effectiveness and superiority of IGOA-SVM to identify transformer fault states by comparing with PSO-SVM and GOA-SVM.

Grasshopper (Orthoptera: Acridomorpha) diversity in response to fallow-land use in southern Cameroon with recommendations for land management.

The sensitivity of grasshoppers to disturbance makes them useful bioindicators for land management. The current study compared the grasshopper communities of three fallow-lands at different levels of human pressure: heavily used land (Ongot), moderately used land (Zamakoe), and least-used land (Ngutadjap). Grasshoppers were sampled by nets, pitfall traps, and box quadrats. Their species composition was analyzed using species-richness, abundance, abundance distribution-model, occurrence, and diversity indexes. Species number was not very different between localities. However, the opening up of forests by human activities offers suitable environment for the development or proliferation of the pest grasshopper populations such as Zonocerus variegatus (Linnaeus, 1758), Eyprepocnemis plorans (Charpentier, 1825), and Catantops sylvestrisJago, 1984, which are adapted to the very common Asteraceae found in fallow lands. Native forest species [such as Mazaea granulosa Stål, 1876, Holopercna gerstaeckeri (Bolívar, 1890), Digentia fasciataRamme, 1929] were, generally absent or rare and were collected in only forest/fallow-land ecotones. Low abundance and low occurrence of ecotone species fitted the log-normal abundance distribution model. The grasshopper communities of the less degraded localities were quite similar, but different from the Ongot community. Forest management by reforestation, reduction of slash-and-burn agriculture, and wood cutting, would restore the original grasshopper assemblages and general environmental health.

Assessment on Potential Suitable Habitats of the Grasshopper Oedaleus decorus asiaticus in North China based on MaxEnt Modeling and Remote Sensing Data.

Grasshopper populations can quickly grow to catastrophic levels, causing a huge amount of damage in a short time. Oedaleus decorus asiaticus (Bey-Bienko) (O. d. asiaticus) is the most serious species in Xilingol League of the Inner Mongolia Autonomous Region. The region is not only an important grassland but also a site of agricultural heritage systems in China. Therefore, projecting the potential geographic distribution of O. d. asiaticus to provide an early warning is vital. Here, we combined temperature, precipitation, soil, vegetation, and topography with remote sensing data to screen the predictors that best characterize the current geographical distribution of O. d. asiaticus. A MaxEnt model approach was applied to project the potential suitable distribution of O. d. asiaticus in Xilingol League (the Inner Mongolia Autonomous Region of China) combined with a set of optimized parameters. The modeling results indicated that there were six main habitat factors that determined the suitable distribution of O. d. asiaticus such as the soil type (ST), grassland type (GT), elevation, precipitation during the growing period (GP), precipitation during the spawning period (SP), and normalized difference vegetation index during the overwintering period (ONDVI). The simulated result was good, with average AUC and TSS values of 0.875 and 0.812, respectively. The potential inhabitable areas of grasshoppers were 198,527 km2, distributed mainly in West Urumqi, Xilinhot City, East Urumqi, Abaga Banner, and Xianghuang Banner of Xilingol League. This study is valuable to guide managers and decision-makers to prevent and control the occurrence of O. d. asiaticus early on and this study may facilitate meaningful reductions in pesticide application.

Effects of Acclimation, Population, and Sex on Behavioral Thermoregulation, CTMax, Symptoms of Heat Stress, and Gene Expression of Melanoplus differentialis, a Generalist Grasshopper—Does Temporal Thermal Heterogeneity Prepare Populations for a Warming World?

Insects thermoregulate using both canalized and plastic mechanisms. Populations of insects utilize these mechanisms to different extents, and while it is posited that the degree of thermal fluctuation a population experiences can determine the optimal combination of mechanisms to utilize, this is still being elucidated. We used three populations of the generalist grasshopper, Melanoplus differentialis, from sites experiencing different degrees of thermal heterogeneity to test for correlations between thermal heterogeneity and 1) behavioral thermoregulation, 2) upper temperature tolerance, 3) the ability to thermally acclimate, and 4) gene expression. We found that 1) behavioral thermoregulation did not differ among sites, 2) CTMax of males, but not females, was higher at more thermally heterogeneous sites, 3) there was acclimation in some of the tested traits, but thermally heterogeneous sites did not always have the most plastic individuals, and 4) there were differences in gene expression among sites, but these differences were not between the most and least thermally heterogeneous sites. We concluded that thermal heterogeneity may play a selective role in some, but not all, of the measured thermoregulatory traits and their plasticity.

Insecticidal Management of Rangeland Grasshoppers Using a Remotely Piloted Aerial Application System

Grasshoppers are integral parts of rangeland ecosystems but also have the potential to reach population densities high enough (outbreaks) to cause serious economic damage from forage loss and affect adjacent crops. The objective of this study was to investigate the efficacy of treating grasshopper population hotspots with a liquid insecticide using a remotely piloted aerial application system (RPAAS), as opposed to fixed-wing aircraft, which is the most common method currently in use. A liquid insecticide, Sevin XLR PLUS (containing carbaryl), was applied on replicated 4.05-hectare (10-acre) plots with an RPAAS on a ranch in New Mexico. Our results demonstrated that Sevin XLR PLUS significantly suppressed grasshopper populations over a 14-day period (normalized population reduction was 79.11 ± 8.35% SEM) and quite rapidly (mostly by day 3) compared to untreated controls. These results are comparable to those achieved with fixed-wing aircraft. The RPAAS covered the whole test area in a single flight in approximately 5 min, making these population hotspot treatment applications relatively rapid, potentially more cost-effective, and more targeted in comparison to fixed-wing aircraft. Before adoption as an application method option, further research is recommended on using an RPAAS to cover larger areas in combination with using diflubenzuron-based insecticides, which are often preferred.

Grasshoppers exhibit asynchrony and spatial non-stationarity in response to the El Niño/Southern and Pacific Decadal Oscillations

Grasshoppers are preeminent herbivores and perhaps the most significant rangeland pests in the United States (US). Despite the important ecosystem functions they provide, grasshopper populations often obtain densities that cause significant economic harm to grazing operations and agricultural production. Although numerous studies conducted at the level of individual field sites have examined potential mechanisms contributing to grasshopper population “boom and bust” cycles, there has yet to be a large, regional scaled analysis that quantified grasshopper variation across the Western US as a whole. While taking steps to account for data collection biases, mediating effects, and variable confounding, we assessed the influence of Pacific Ocean sea surface temperature oscillations on a 40-year record of grasshopper density in the Western US. Central to our analysis was employing spatially varying coefficients to model time and location-specific variation in grasshopper response to climate. Our results quantitatively demonstrated interannual changes in grasshopper density to be indirectly effected by seasonal El Niño/Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) variability and to exhibit spatial asynchrony and non-stationarity such that the relative influence of climate on grasshopper density varied through time and across geographic space. Our model is the first to incorporate climate indices as spatially varying coefficients for assessment of a terrestrial species and represents a critical step towards understanding causal drivers of regional grasshopper density.

Evolutionary history and colonization patterns of the wing dimorphic grasshopper Dichroplus vittatus in two Argentinean biomes

Quaternary climate oscillations and modification of the environment by humans have played an important role in shaping species distribution and genetic structure of modern species. Here, population genetic parameters were inferred from the analysis of 168 individuals belonging to 11 populations of the South American grasshopper, Dichroplus vittatus, distributed in two Argentinean Biomes (Grassland and Savanna), by sequencing a 543 bp of the mitochondrial COI gene. Overall, we detected considerable haplotype diversity and low nucleotide diversity. AMOVA analyses showed a significant degree of differentiation among Biomes and between populations. Two major mitochondrial lineages can be distinguished. The haplogroup containing the most common haplotype split 17,000 years BP while the haplogroup including the second most common haplotype has a divergence date of about 11,700 years. Approximate Bayesian Computation (ABC) analyses showed that the palaeodemographic scenario that best fitted our data is consistent with a hypothesis of divergence from an ancestral population and subsequent admixture with Grassland-Savanna (South–North) direction. Our results suggest that populations located in both Biomes would derive from a single ancestral population that colonized the region after the Last Glacial Maximum and Grassland would have a more ancestral origin than Savanna. Further, our results emphasize the importance of human-mediated dispersal in the reconfiguration of genetic diversity of species with potential pest capacity.

Exploring the Relationships between South Texas Northern Bobwhite Populations and Cecal Worms via System Dynamics

Community ecology historically focused on plants and free-living organisms; however, problems such as defining habitat boundaries and obtaining adequate sample sizes arise when evaluating such communities. The unique nature of host-helminth systems allows parasite community ecologists to avoid these problems when testing ecological hypotheses. Unlike free-living communities that have artificially constructed boundaries, parasite communities have well-defined unambiguous boundaries within host individuals. Due to the inherently complex and dynamic nature of ecological systems, traditional experimental methods often require expensive, long-term trials beyond investigators’ time and resource budgets. Conversely, a system dynamics approach facilitates learning about such systems via simulation of ecosystem processes integrated with historical data (both quantitative and qualitative). Relatively few studies focus on parasites in South Texas, USA, although research on avian host-parasite systems has shown that parasites can potentially regulate host populations. The northern bobwhite (Colinus virginianus; hereafter, bobwhite) is a game species of ecological, economic, cultural, and recreational importance in Texas that has been experiencing a long-term, widespread decline. To holistically examine the bobwhite-helminth system in South Texas, we created a system dynamics model capturing the feedback relationships between a South Texas bobwhite population, a grasshopper (family Acrididae) population, and the corresponding cecal worm (Aulonocephalus pennula) populations on a hypothetical 1,000-acre ranch in South Texas. The model structure, constructed in Vensim® PLE 7.2 software (Ventana Systems, Inc.), integrates the hypothesized biotic and abiotic drivers (precipitation, parasite load, insect abundance, and quail density) unique to the host-helminth system over 7 years (2012–2019). Our specific objectives were to 1) develop a working baseline model to replicate the synergistic population dynamics among bobwhite, grasshopper, and cecal worm populations and then 2) test hypotheses about each population’s boom-and-bust cycles resulting from environmental stressors (e.g., drought). Applications of the model can provide landowners and natural resource managers with a better understanding of the complex dynamics occurring among bobwhite, grasshopper, and cecal worm populations in South Texas.

Embryonic Development of Grasshopper Populations Along Latitudinal Gradients Reveal Differential Thermoaccumulation for Adaptation to Climate Warming

Climate warming has a remarkable effect on the distribution, phenology, and development of insects. Although the embryonic development and phenology of non-diapause grasshopper species are more susceptible to warming than those of diapause species, the responses of developmental traits in conspecifically different populations to climate warming remain unknown. Here, we compared the mtDNA sequences and embryonic development of eight populations of grasshopper species (Chorthippus dubius) in field-based manipulated warming and laboratory experiments. The mtDNA sequences showed a significant genetic differentiation of the southernmost population from the other seven populations on the Mongolian Plateau. The embryonic development of the southernmost population was significantly slower than those of the northern populations at the same incubation temperatures. Interestingly, laboratory experiments showed that a significant difference exists in the effective accumulated degree days (EADD) but not in the lower development threshold temperatures (LDTT) among the different populations. The high-latitude populations required less EADD than the low-latitude populations. The warming treatments significantly accelerated the embryonic development in the field and decreased duration from embryos to hatchlings of all eight populations in the incubation. In addition, warming treatments in field significantly increased EADD requirement per stage in the incubation. Linear regression model confirmed that the embryonic development characteristics of eight populations were correlated with the annual mean temperature and total precipitation of embryonic development duration. The results indicated that grasshopper species have evolved a strategy of adjusting their EADD but not their LDTT to adapt to temperature changes. The variations in the EADD among the different populations enabled the grasshopper eggs to buffer the influences of higher temperatures on development and preserve their univoltine nature in temperate regions while encountering warmer climatic conditions. Thus, the findings of this study is valuable for our understanding species variation and evolution, and as such has direct implication for modeling biological response to climate warming.

High-Elevation Populations of Montane Grasshoppers Exhibit Greater Developmental Plasticity in Response to Seasonal Cues.

Populations of insects can differ in how sensitive their development, growth, and performance are to environmental conditions such as temperature and daylength. The environmental sensitivity of development can alter phenology (seasonal timing) and ecology. Warming accelerates development of most populations. However, high-elevation and season-limited populations can exhibit developmental plasticity to either advance or prolong development depending on conditions. We examine how diurnal temperature variation and daylength interact to shape growth, development, and performance of several populations of the montane grasshopper, Melanoplus boulderensis, along an elevation gradient. We then compare these experimental results to observed patterns of development in the field. Although populations exhibited similar thermal sensitivities of development under long-day conditions, development of high-elevation populations was more sensitive to temperature under short-day conditions. This developmental plasticity resulted in rapid development of high elevation populations in short-day conditions with high temperature variability, consistent with their observed capacity for rapid development in the field when conditions are permissive early in the season. Notably, accelerated development generally did not decrease body size or alter body shape. Developmental conditions did not strongly influence thermal tolerance but altered the temperature dependence of performance in difficult-to-predict ways. In sum, the high-elevation and season-limited populations exhibited developmental plasticity that enables advancing or prolonging development consistent with field phenology. Our results suggest these patterns are driven by the thermal sensitivity of development increasing when days are short early in the season compared to when days are long later in the season. Developmental plasticity will shape phenological responses to climate change with potential implications for community and ecosystem structure.

Spatial population structure: patterns of adaptation in populations of the water hyacinth grasshopper Cornops aquaticum (Bruner 1906)

AbstractThe water hyacinth grasshopper Cornops aquaticum (Bruner 1906) constitutes an appropriate model to assess phenotypic and karyotypic variability in the context of differentiation and adaptation of insect populations because it occurs over a wide latitudinal range. This study represents a general analysis of phenotype, karyotype and molecular variation in native populations of C. aquaticum in South America. This is also relevant because this insect is considered a promising biological control agent of water hyacinth, a native South American aquatic plant but a pest in South Africa. Along Paraná and Uruguay River Basins, body size correlated negatively with latitude, and positively so with temperature and rainfall in both sexes. To test whether the chromosomal and phenotypic patterns were adaptive, we compared them with neutral microsatellite loci variation in populations from the medium and lower course of the Paraná River. Firstly, the lack of pairwise association between karyotype and phenotype distance matrixes with that of neutral loci suggested non-neutrality. Secondly, phenotypic differentiation for all morphometric traits (PST) was significantly larger than molecular differentiation (FST), indicating a prevailing divergence selection effect on the observed phenotypic patterns. Finally, the phenotypic and genotypic spatial structures – inferred from Bayesian approaches – were discordant: neutral genetic structure clustered together most populations except for the two southernmost, downstream ones, whereas phenotypic spatial structure groups together all the deltaic populations and singles out the two northernmost ones. The results suggest directional selection leading to higher centric fusion frequencies in the downstream populations and favouring morphometric optimal differences in relation to the environment.

Use of aqueous plant extracts to reduce profenofos residues in the leaf of mustard (Brassica juncea L.) and suppression of the grasshopper population

Profenofos is an active ingredient from the organophosphate group which residue is often found in various fresh and processed vegetable products. This study aimed to assess the use of aqueous plant extracts of Sapindus rarak seeds, Luffa acutangula peel and Centella asiatica leaves to reduce profenofos residues in leaf of mustard and to evaluate their performance in suppressing the grasshopper populations. S. rarak seeds, L. acutangula peels and C. asiatica leaves were dried and filtered using a 100 mesh sieve. A total of 30 gm samples of each ingredient were mixed with 1000 ml of water and blended at 800 rpm, then filtered using 100 mesh sieve before use. The field experiment was performed by spraying profenofos pesticide with a concentration of 3 ml l-1 at a dose of 30 ml per plant. Two days after the profenofos application, the plants were sprayed with the aqueous plant extracts. Twenty-four hrs aqueous plant extracts application, pesticide residues were detected by the UPLC-MS/MS machine. The phytotoxicity test results showed that the use of aqueous plant extracts at a dose of 30 ml per plant did not cause any phytotoxic symptoms. Furthermore, in the field experiment, the control plants showed a residual value of 2407.62 ng g-1. Results of UPLC-MS/MS showed that the residual value of profenofos in PL treatment (aqueous extract of S. rarak seeds) was 1502.05 ng g-1, the recorded residual value in the PP treatment (aqueous extract of C. asiatica leaves) was 1316.27 ng g-1 and the residual value in the PG treatment (aqueous extract of L. acutangula peels) was 660.71 ng g-1. In the treated plants, the residual value decreased from 37.48% to 72.55%. Furthermore, the number of grasshoppers after the PL treatment decreased and was significantly different from the control. This study provides new information that aqueous plant extracts can reduce the residue of profenofos and suppress the population of grasshoppers in the mustard leaf.

Modeling Rangeland Grasshopper (Orthoptera: Acrididae) Population Density Using a Landscape-Level Predictive Mapping Approach.

Since the mid-19th century, grasshoppers have posed a substantial threat to North American rangelands as well as adjacent croplands and have the potential to cost the economy millions of dollars in annual damages. The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) have gone to great lengths to ensure that rangeland grasshopper populations remain below an economic impact threshold across the western United States. However, current grasshopper forecasting efforts by the USDA are based solely on the previous year's grasshopper density and do not take region-specific environmental factors (e.g., climate and topography) into account. To better understand the effects of climate and landscape heterogeneity on rangeland grasshopper populations, we assessed the relationship between grasshopper density survey data from across 56 sites between 2007 and 2017 for four counties in north central Wyoming with 72 biologically relevant geographic information system (GIS)-based environmental variables. A regression model was developed to predict mean adult grasshopper density from 2012 to 2016, which was then used to forecast grasshopper density in 2017. The best-fit predictive model selected using Akaike's Information Criterion (AICc) explained 34.5% of the variation in mean grasshopper density from 2012 to 2016. October precipitation and past mean grasshopper density from 2007 to 2011 were among the best predictors of mean grasshopper density in 2012-2016. Our results also suggest that rangelands in central Sheridan County, southwest Johnson County, and southeast Washakie County are more prone to grasshopper outbreaks. Most importantly, this study demonstrated that both biotic and abiotic environmental variables influence grasshopper density and should be considered in future forecasting efforts.