Agricultural Insect Pests Research Articles

Aedes Albopictus (Diptera: Culicidae) Susceptibility Status to Agrochemical Insecticides Used in Durian Planting Systems in Southern Thailand

High rates of dengue morbidity occur in southern Thailand. The intensive application of insecticides in orchards could affect not only agricultural insect pests, but also nontarget mosquitoes or beneficial insects. In this study, the type and quantity of insecticides commonly used across durian plantations in southern Thailand were characterized, along with the population density of Aedes albopictus (Skuse) (Diptera: Culicidae). Our primary aim was to determine the susceptibility status of field-derived Ae. albopictus to typical application concentrations of four agrochemical insecticides; cypermethrin, chlorpyrifos, carbaryl, and imidacloprid. Mosquito eggs were collected from durian cultivation sites in five provinces in southern Thailand and used to generate adults for susceptibility tests. The cultivation sites were categorized into three groups based on insecticide application: intensive application of insecticides, low application of insecticides, and no application of insecticides. Twenty ovitraps were deployed for at least three consecutive days at each study site to collect mosquito eggs and to determine Ae. albopictus population density. WHO tube assays were used to determine the susceptibility of adult mosquitoes derived from field-collected eggs to selected insecticides. This represents the first report of the susceptibility status of Ae. albopictus from durian orchards in southern Thailand to agrochemical insecticides. Results showed complete susceptibility of these Ae. albopictus to chlorpyrifos, but reduced mortality following exposure to λ-cyhalothrin, carbaryl, and imidacloprid, which is suggestive of the development of resistance. These findings provide new insights into the status of insecticide susceptibility in Ae. albopictus populations, with important implications for mosquito and mosquito-borne disease control in Thailand.

First report of voltage‐gated sodium channel M918V and molecular diagnostics of nicotinic acetylcholine receptor R81T in the cotton aphid

AbstractThe cotton aphid, Aphis gossypii Glover, is one of the most important agricultural insect pests. Pyrethroid and neonicotinoid insecticides have generally shown excellent control of A. gossypii, but many populations of this pest have developed resistance against these classes of insecticides. The success of insecticide resistance management strategies requires detailed knowledge of both phenotype and genotype of the target insect pest. In this study, we attempted to understand the molecular status of insecticide resistance in cotton aphid populations in Xinjiang Uygur Autonomous Region of China, the major cotton planting region of China. In addition to the previously reported M918L mutation, we discovered another substitution (M918V) in the voltage‐gated sodium channel (VGSC). Moreover, we developed a molecular assay that could be used to detect precisely the R81T mutation in the nicotinic acetylcholine receptor (nAChR). This survey revealed that 918L was the predominant VGSC allele with a frequency ranging from 50.0% to 56.7%. Notably, appreciable frequencies (between 10% and 40%) of the resistance 81T allele of the nAChR gene were detected in three investigated populations. The prevalent co‐occurrence of both VGSC 918L/V and nAchR 81T indicates a worrisome situation of multiple resistance to both pyrethroids and neonicotinoids.

Insecticidal activity of Pilocarpus spicatus Saint-Hilaire (Rutaceae) essential oil against the crop pest Dysdercus peruvianus (Guérin-Méneville, 1831) and Oncopeltus fasciatus (Dallas, 1852)

Studies were carried out to evaluate the insecticidal activity of Pilocarpus spicatus Saint-Hilaire (Rutaceae) essential oil (EO) on the development of the Hemiptera Dysdercus peruvianus (Guérin-Méneville, 1831) and Oncopeltus fasciatus (Dallas, 1852). Gas Chromatography/Mass spectrometry analysis revealed a chemical composition with sabinene (32.27%) and sylvestrene (27.26%) as major constituents. Topical and continuous treatment with the pure EO induced 100% of mortality while serial dilutions of the EO induced different levels of lethality in a dose response manner. Median lethal dose (LD50) and lethal dose 90% (LD90) were determined. Malformations in insects and permanent or supernumerary nymphs were often observed after treatments, and the use of scanning electron microscopy allowed the analysis of morphological changes. The different biological effects of P. spicatus EO point out its potential as a rich source of bioactive molecules to be used as an alternative control method against agricultural pest insects.

Precise single base substitution in the shibire gene by CRISPR/Cas9-mediated homology directed repair in Bactrocera tryoni

BackgroundPest eradication using the Sterile Insect Technique (SIT) involves high-density releases of sterilized males that mate with wild females and ultimately suppress the population. Sterilized females are not required for SIT and their removal or separation from males prior to release remains challenging. In order to develop genetic sexing strains (GSS), conditional traits such as temperature sensitive lethality are required.ResultsHere we introduce a known Drosophila melanogaster temperature sensitive embryonic lethal mutation into Bactrocera tryoni, a serious horticultural pest in Australia. A non-synonymous point mutation in the D. melanogaster gene shibire causes embryonic lethality at 29 °C and we successfully used CRISPR/Cas9 technology to recreate the orthologous shibire temperature sensitive-1 (shits1) mutation in B. tryoni. Genotypic analyses over three generations revealed that a high fitness cost was associated with the shits1 mutant allele and shits1 homozygotes were not viable at 21 °C, which is a more severe phenotype than that documented in D. melanogaster.ConclusionsWe have demonstrated the first successful use of CRISPR/Cas9 to introduce precise single base substitutions in an endogenous gene via homology-directed repair in an agricultural pest insect and this technology can be used to trial other conditional mutations for the ultimate aim of generating genetic sexing strains for SIT.

Improvement on the genetic engineering of an invasive agricultural pest insect, the cherry vinegar fly, Drosophila suzukii

BackgroundThe invasive fly Drosophila suzukii has become an established fruit pest in Europe, the USA, and South America with no effective and safe pest management. Genetic engineering enables the development of transgene-based novel genetic control strategies against insect pests and disease vectors. This, however, requires the establishment of reliable germline transformation techniques. Previous studies have shown that D. suzukii is amenable to transgenesis using the transposon-based vectors piggyBac and Minos, site-specific recombination (lox/Cre), and CRISPR/Cas9 genome editing.ResultsWe experienced differences in the usability of piggyBac-based germline transformation in different strains of D. suzukii: we obtained no transgenic lines in a US strain, a single rare transgenic line in an Italian strain, but observed a reliable transformation rate of 2.5 to 11% in a strain from the French Alps. This difference in efficiency was confirmed by comparative examination of these three strains. In addition, we used an attP landing site line to successfully established φC31-integrase-mediated plasmid integration at a rate of 10% and generated landing site lines with two attP sequences to effectively perform φC31-Recombinase Mediated Cassette Exchange (φC31-RMCE) with 11% efficiency. Moreover, we isolated and used the endogenous regulatory regions of Ds nanos to express φC31 integrase maternally to generate self-docking lines for φC31-RMCE. Besides, we isolated the promoter/enhancer of Ds serendipity α to drive the heterologous tetracycline-controlled transactivator (tTA) during early embryonic development and generated a testes-specific tTA driver line using the endogenous beta-2-tubulin (β2t) promoter/enhancer.ConclusionOur results provide evidence that the D. suzukii strain AM derived from the French Alps is more suitable for piggyBac germline transformation than other strains. We demonstrated the feasibility of using φC31-RMCE in the cherry vinegar fly and generated a set of lines that can be used for highly efficient integration of larger constructs. The φC31-based integration will facilitate modification and stabilization of previously generated transgenic lines that carry at least one attP site in the transgene construction. An early embryo-specific and a spermatogenesis-specific driver line were generated for future use of the binary expression system tet-off to engineer tissue- and stage-specific effector gene expression for genetic pest control strategies.

The Invasion and Encapsulation of the Entomopathogenic Nematode, Steinernema abbasi, in Aedes albopictus (Diptera: Culicidae) Larvae.

Simple SummaryThe Asian tiger mosquito, Aedes albopictus, is widely considered to be one of the most dangerous vectors transmitting human diseases. Meanwhile, entomopathogenic nematodes (EPNs) have been applied for controlling insect pests of agricultural and public health importance for years. However, infection of mosquitoes with the infective juveniles (IJs) of terrestrial-living EPNs when released to aquatic habitats needs further investigated. In this study, we observed that a Taiwanese isolate of EPN, Steinernema abbasi, could invade through oral route and then puncture the wall of gastric caecum to enter the body cavity of Ae. albopictus larvae. The nematode could complete infection of mosquitoes by inserting directly into trumpet, the intersegmental membrane of the cuticle, and the basement of the paddle of pupae. After inoculation of mosquito larvae with nematode suspensions, the invading IJs in the hemocoel were melanized and encapsulated and only a few larvae were able to survive to adult emergence. The mosquitocidal effect of S. abbasi could be due to its overload or destruction of the mosquito defense systems. Eventually, the mosquito larvae failed to recover and died a few days after infection. Our results suggest that the terrestrial EPN, S. abbasi, is effective against the aquatic living mosquitoes.The Asian tiger mosquito, Aedes albopictus, is of crucial concern to the public and veterinary health because of its vector role in transmission of several mosquito-borne diseases. Over the past decades, entomopathogenic nematodes (EPNs) have been used to control important agricultural insect pests and are considered to be effective against mosquitoes as well. The objectives of this study were to investigate the mosquitocidal effects of Steinernema abbasi to Ae. albopictus and the encapsulation processes of invading nematodes in the mosquito host. In this study, we found that S. abbasi was pathogenic to 3rd and 4th instar larvae of Ae. albopictus by entering the hemocoel of the 3rd and 4th instar larvae mainly through mouth and gastric caecum or by penetrating pupae through the intersegmental membrane or trumpet. The mosquito larvae infected with a single nematode caused a high mortality. Although EPNs in the hemocoel of mosquitoes were melanized and encapsulated, most Ae. albopictus larvae failed to survive after infection with S. abbasi. Overall, we demonstrated that S. abbasi is pathogenic to Ae. albopictus larvae, suggesting that this S. abbasi isolate has potential as a biocontrol agent for managing this vector mosquito.

RNAi-Mediated Suppression of Laccase2 Impairs Cuticle Tanning and Molting in the Cotton Boll Weevil (Anthonomus grandis).

The cotton boll weevil, Anthonomus grandis, is the most economically important pest of cotton in Brazil. Pest management programs focused on A. grandis are based mostly on the use of chemical insecticides, which may cause serious ecological impacts. Furthermore, A. grandis has developed resistance to some insecticides after their long-term use. Therefore, alternative control approaches that are more sustainable and have reduced environmental impacts are highly desirable to protect cotton crops from this destructive pest. RNA interference (RNAi) is a valuable reverse genetics tool for the investigation of gene function and has been explored for the development of strategies to control agricultural insect pests. This study aimed to evaluate the biological role of the Laccase2 (AgraLac2) gene in A. grandis and its potential as an RNAi target for the control of this insect pest. We found that AgraLac2 is expressed throughout the development of A. grandis with significantly higher expression in pupal and adult developmental stages. In addition, the immunolocalization of the AgraLac2 protein in third-instar larvae using specific antibodies revealed that AgraLac2 is distributed throughout the epithelial tissue, the cuticle and the tracheal system. We also verified that the knockdown of AgraLac2 in A. grandis resulted in an altered cuticle tanning process, molting defects and arrested development. Remarkably, insects injected with dsAgraLac2 exhibited defects in cuticle hardening and pigmentation. As a consequence, the development of dsAgraLac2-treated insects was compromised, and in cases of severe phenotypic defects, the insects subsequently died. On the contrary, insects subjected to control treatments did not show any visible phenotypic defects in cuticle formation and successfully molted to the pupal and adult stages. Taken together, our data indicate that AgraLac2 is involved in the cuticle tanning process in A. grandis and may be a promising target for the development of RNAi-based technologies.

Seasonal Fluctuations and Management of Sucking Insect Pests on Bitter Gourd (Momordica charantia L.)

Background: Bitter gourd, an important tropical and sub-tropical vegetable which occupies a predominant position in Indian vegetables. The aphids and leafhoppers are more serious agricultural insect pests and aphids indirectly transmit plant virus diseases like, Cucumber Mosaic Virus (CMV) in cucurbit crops. Our study aimed to noticed seasonal fluctuations and bio-inputs using management of sucking pests in bitter gourd.Methods: Field experiments were conducted during 2017-19 in a farmer’s field at Ellamanam village, Tiruchirappalli district, Tamil Nadu in insect pest population was monitored at weekly intervals from ten randomly selected plants in three plots. In field efficacy studies conducted Randomised Block Design with eight treatments and three replications. Result: Our results showed in the maximum aphid and leafhopper populations were recorded in September 2018 during 39th SMW (Standard Meteorological Week). In Rabi, the aphids and leaf hopper population were maximum in 9th and 10th SMW in February and March. The population of aphids and leafhopper were positively correlated with maximum temperature, minimum temperature, wind speed and wind direction. Rainfall and relative humidity were negatively associated to aphids and leafhopper infestation. In Kharif and Rabi, high reduction of aphid and leafhopper pest population were noticed in chlorantraniliprole 18.5 SC and spinosad 45 SC compared to control. Among the bio-inputs agniastram recorded higher reduction of pest population followed by karpurakaraisal, NSKE, fish acid and ten leaf extract.

Gene Characterization and Enzymatic Activities Related to Trehalose Metabolism of In Vitro Reared Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) under Sustained Cold Stress.

Simple SummaryTrehalose is a non-reducing disaccharide that presents in a wide variety of organisms, where it serves as an energy source or stress protectant. Trehalose is the most characteristic sugar of insect hemolymph and plays a crucial role in the regulation of insect growth and development. Trichogramma species are economically important egg parasitoids, which are being mass-produced for biological control programs worldwide. Many Trichogramma species could be mass reared on artificial mediums (not insect eggs), in which components contain insect hemolymph and trehalose. These in vitro-reared parasitoid wasps were strongly affected by cold storage, but prepupae could be successfully stored at 13 °C for up to 4 weeks. The aims of the present study were to determine the role of trehalose and the relationship between trehalose and egg parasitoid stress resistance. Our study revealed that (1) trehalose regulated the growth under sustained cold stress; (2) prepupal stage is a critical developmental period and 13 °C is the cold tolerance threshold temperature; (3) in vitro reared Trichogramma dendrolimi could be reared at temperatures of 16 °C, 20 °C, and 23 °C to reduce rearing costs. This finding identifies a low cost, prolonged development rearing method for T. dendrolimi, which will facilitate improved mass rearing methods for biocontrol.Trichogramma spp. is an important egg parasitoid wasp for biocontrol of agriculture and forestry insect pests. Trehalose serves as an energy source or stress protectant for insects. To study the potential role of trehalose in cold resistance on an egg parasitoid, cDNA for trehalose-6-phosphate synthase (TPS) and soluble trehalase (TRE) from Trichogramma dendrolimi were cloned and characterized. Gene expressions and enzyme activities of TdTPS and TdTRE were determined in larvae, prepupae, pupae, and adults at sustained low temperatures, 13 °C and 16 °C. TdTPS and TdTRE expressions had similar patterns with higher levels in prepupae at 13 °C and 16 °C. TdTPS enzyme activities increased with a decrease of temperature, and TdTRE activity in prepupae decreased sharply at these two low temperatures. In vitro reared T. dendrolimi could complete entire development above 13 °C, and the development period was prolonged without cold injury. Results indicated trehalose might regulate growth and the metabolic process of cold tolerance. Moreover, 13 °C is the cold tolerance threshold temperature and the prepupal stage is a critical developmental period for in vitro reared T. dendrolimi. These findings identify a low cost, prolonged development rearing method, and the cold tolerance for T. dendrolimi, which will facilitate improved mass rearing methods for biocontrol.

Toxicological Effects of five Insecticides on Cabbage Aphid, Brevicoryne brassicae (L.) (Homoptera: Aphididae) and its Parasitoid Aphelinus sp. (Hymenoptera:Aphelinidae)

Cabbage aphid, Brevicoryne brassicae (L.) is an important agricultural insect pest that attacks many vegetable crops all over the world. Herein, the study was conducted to evaluate the efficacy of five insecticides, acetameprid 20% SP (neonicotinoid), abamactin 1.8% EC (avermectin), indoxicarb 15% EC (oxadiazine), chlorpyrifos methyl 50%EC (organophosphate) and lambda cyhalothrin 5% EC (pyrethroid) against cabbage aphids Brevicoryne brassicae (L.) and its parasitoid Aphelinus sp. under laboratory conditions. Mortality percentages for both cabbage aphid and parasitoid were determined after 24, 48 and 72-h after treatment. Result revealed that acetamiprid was the greatest toxic insecticide against cabbage aphid followed by abamectin and indoxacarb after 24 and 48-h of treatment. Otherwise, lambda cyhalothrin followed by chlorpyrifos methyl was the lowest toxicity on cabbage aphid after 24 and 48-h from treatment. In contrast, toxicological results for parasitoid suggested that acetamiprid had less toxicity followed by abamectin and indoxacarb after 24 and 48-h of treatment. whereas, lambda cyhalothrin followed by chlorpyrifos methyl demonstrated great toxicity on the parasitoid after 24 and 48-h of treatment. In addition, safety factor for each treatment was determined, and results revealed that greater safety factor was recorded for acetamiprid, abamectin and indoxacarb than chlorpyrifos methyl and lambda cyhalothrin. Thus, these results suggest that acetamiprid can be included in the Integrated Pest Management (IPM) Program against cabbage aphid with safe side and minimum harmful effect on its parasitoid.

Microbiome Innovation in Agriculture: Development of Microbial Based Tools for Insect Pest Management

According to the Entomological Society of America’s (ESA) recent position statement, invasive insects incur control costs of over $2.5 billion and cause economic damages to crops, lawns, forests, and pastures totaling $18 billion per year (“The Not-So-Hidden Dangers of Invasive Species” 2018). The threat of invasive crop pests to food security continues to be driven by complex dynamics of human movements, global trade activities, climate change, and changing agricultural practices. Chemical insecticides have been central to crop protection against invasive insects. However, a growing demand for reduced agricultural chemical use due to environmental and human health concerns in addition to pesticide resistance issues are fueling interests in innovative approaches to manage invasive pests. For decades, the role of microbes in pest management has been largely confined to using entomopathogens, with only a handful of microbial species being developed into bioinsecticides. The paradigm is shifting owing to the advent of high-throughput sequencing, functional omics, and gene editing technologies, which greatly accelerate microbial discovery, as well as a better understanding of microbial functions in complex communities across different habitats. There is also overwhelming evidence that symbiotic microbes play pivotal roles in shaping various insect traits. The collection of microbes associated with a given environment (both biotic and abiotic) and their collective genetic materials is termed the microbiome. In this paper, we survey the latest development in microbiome research that could be leveraged into novel management tools for agricultural insect pests (Figure 1). We first review the diverse insect traits shaped by insect-microbe associations that span nutrition, immunity, ecological interactions with natural enemy, insecticide resistance, and behavior. This is followed by a discussion on different microbiome manipulation approaches to alter pest traits, describing some of the opportunities and obstacles for each approach. We then highlight microbiomes as untapped chemical inventories to discover novel biopesticides, including plant-incorporated protectants and semiochemicals. The last topic covered is the use of beneficial microbes to improve performance of mass-reared insects for autocidal programs, including sterile insect technique and incompatible insect technique, in which we identify topics where data are limited or inconclusive for future research.

Land cover and climate changes drive regionally heterogeneous increases in US insecticide use

Global environmental change is expected to dramatically affect agricultural crop production through a myriad of pathways. One important and thus far poorly understood impact is the effect of land cover and climate change on agricultural insect pests and insecticides. Here we address the following three questions: (1) how do landscape complexity and weather influence present-day insecticide use, (2) how will changing landscape characteristics and changing climate influence future insecticide use, and how do these effects manifest for different climate and land cover projections? and (3) what are the most important drivers of changing insecticide use? We use panel models applied to county-level agriculture, land cover, and weather data in the US to understand how landscape composition and configuration, weather, and farm characteristics impact present-day insecticide use. We then leverage forecasted changes in land cover and climate under different future scenarios to predict insecticide use in 2050. We find different future scenarios—through modifications in both landscape and climate conditions—increase the amount of area treated by ~ 4–20% relative to 2017, with regionally heterogeneous impacts. Of note, we report large farms are more influential than large crop patches and increased winter minimum temperature is more influential than increased summer maximum temperature. However, our results suggest the most important determinants of future insecticide use are crop composition and farm size, variables for which future forecasts are sparse. Both landscape and climate change are expected to increase future insecticide use. Yet, crop composition and farm size are highly influential, data-poor variables. Better understanding of future crop composition and farm economics is necessary to effectively predict and mitigate increases in pesticide use.

Comparative pathogenicity of four entomopathogenic fungal species against nymphs and adults of citrus red mite on the citrus plantation

Panonychus citri (citrus red mite) is a devastating pest of citrus orchards. The conventional chemical acaricides have been strongly forbidden for the management of agricultural insect pests in China. Therefore, we evaluated the susceptibility of adult and nymphs P. citri in laboratory against eight isolates of four fungal species, Akanthomyces lecanii, Metarhizium anisopliae, Beauveria bassiana and Aschersonia aleyrodis. Each citrus seedling having 40 adults (2-d-old) and nymphs (on separate plants) were sprayed with isolates at the concentration of 104 ~ 108 conidia mLˉ1 whereas controlled seedlings were sprayed with 0.02% Tween-80. After 9 days of fungal exposure, the four fungal isolates caused more than 50% mortality of mites, such as; 85.6%, 87.9%, 64.6% and 79.7% by A. lecanii (V3450), B. bassiana (BFZ0409), M. anisopliae (MFZ0706) and A. aleyrodis (AsG0910), respectively. The nymphal mites were less susceptible to applied fungi compared to adults. The LC50s of the tested isolates were determined by the fitted time-concentration-mortality relationships, which declined over days after spray. LT50s were decreased with a high concentration of isolates. After the 9-d inoculation, two isolates of B. bassiana (BFZ0409 and D1344) and one isolate of A. lecanii (V3450) were highly effective at the minimal dose of LC50 of 104 conidia mLˉ1 and are promising candidates to control mites, as compared to other tested fungal isolates.

Endogenous Viral Element-Derived Piwi-Interacting RNAs (piRNAs) Are Not Required for Production of Ping-Pong-Dependent piRNAs from Diaphorina citri Densovirus.

Piwi-interacting RNAs (piRNAs) are a class of small RNAs primarily responsible for silencing transposons in the animal germ line. The ping-pong cycle, the posttranscriptional silencing branch of the piRNA pathway, relies on piRNAs produced from endogenous transposon remnants to direct cleavage of transposon RNA via association with Piwi-family Argonaute proteins. In some mosquito species and mosquito-derived cell lines expressing a functionally expanded group of Piwi-family Argonaute proteins, both RNA and DNA viruses are targeted by piRNAs in a manner thought to involve direct processing of exogenous viral RNA into piRNAs. Whether viruses are targeted by piRNAs in nonmosquito species is unknown. Partial integrations of DNA and nonretroviral RNA virus genomes, termed endogenous viral elements (EVEs), are abundant in arthropod genomes and often produce piRNAs that are speculated to target cognate viruses through the ping-pong cycle. Here, we describe a Diaphorina citri densovirus (DcDV)-derived EVE in the genome of Diaphorina citri We found that this EVE gives rise to DcDV-specific primary piRNAs and is unevenly distributed among D. citri populations. Unexpectedly, we found that DcDV is targeted by ping-pong-dependent virus-derived piRNAs (vpiRNAs) in D. citri lacking the DcDV-derived EVE, while four naturally infecting RNA viruses of D. citri are not targeted by vpiRNAs. Furthermore, a recombinant Cricket paralysis virus containing a portion of the DcDV genome corresponding to the DcDV-derived EVE was not targeted by vpiRNAs during infection in D. citri harboring the EVE. These results demonstrate that viruses can be targeted by piRNAs in a nonmosquito species independently of endogenous piRNAs.IMPORTANCE Small RNAs serve as specificity determinants of antiviral responses in insects. Piwi-interacting RNAs (piRNAs) are a class of small RNAs found in animals, and their primary role is to direct antitransposon responses. These responses require endogenous piRNAs complementary to transposon RNA. Additionally, piRNAs have been shown to target RNA and DNA viruses in some mosquito species. In contrast to transposons, targeting of viruses by the piRNA pathway in these mosquito species does not require endogenous piRNAs. Here, we show that piRNAs target a DNA virus, but not RNA viruses, in an agricultural insect pest. We found that targeting of this DNA virus did not require endogenous piRNAs and that endogenous piRNAs did not mediate targeting of an RNA virus with which they shared complementary sequence. Our results highlight differences between mosquitoes and our experimental system and raise the possibility that DNA viruses may be targeted by piRNAs in other species.

DEVELOPMENT OF MICROSPORIDIOLOGY IN RUSSIA

The study of microsporidia and microsporidioses of wild animals in Russia has been initiated in the 60-s of the past century. In the European part of country, microsporidia, infecting agricultural insect pests (All-Russian Institute of Plant Protection), freshwater arthropods and fishes (State Research Institute of Lake and River Fisheries) and the blood-sucking insects such as horseflies (Biology Institute, Karelian Scientific Center) were studied. In the Western Siberia, microsporidia of blood-sucking mosquitoes were studied (Tomsk University). As a result, by 2000, as many as 118 species and 47 genera of microsporidia were found, including 20 taxa new to science, from 100 animal species. Currently, descriptions of new taxa and taxonomic revision of the previously described taxa are performed using the molecular phylogenetic analysis. The novel data on speciation of microsporidia have been obtained, and the coevolution of parasites and their host insects have been confirmed for microsporidia of blood-sucking mosquitoes. During the study of the structure and physiology of microsporidia, it has been demonstrated, that the secretory proteins of microsporidia migrate into the nucleus of the host cell; the factors of parasites suppressing host cell apoptosis and the presence of specific organelles related to the energy metabolism have been revealed; the mitosomes have been found in the spores and not the prespore stages of microsporidia. The role of the Golgi complex in the formation of the extrusion apparatus, as well as the absence of the vesicular secretory transport in microsporidia, has been shown for the first time. For the first time in Russia, cases of microsporidia infection in HIV-infected patients have been identified. Currently, attention is paid to the development of a new universal taxonomic system of microsporidia combining molecular characteristics with a description of the structural and developmental features of each taxon of the parasites. Microsporidia possess many remarkable structural and functional differences from any other organisms thus substantiating an independent field of biological research: “microsporidiology”.

Behaviour of neonicotinoids in contrasting soils

Neonicotinoids are widely used to control insect pests in agriculture. Their presence in the environment can affect the health of non-target insects and aquatic animals. The behaviour of four neonicotinoids, namely imidacloprid, acetamiprid, thiacloprid and thiamethoxam, has been investigated in soils with contrasting characteristics to understand their migration in soil and ecological risk. Among the study neonicotinoids, thiamethoxam and thiacloprid were found to be the least and most sorbed neonicotinoids by all the soils, respectively (up to 186 time greater adsorption of thiacloprid), and their uptake was affected by the content of organic matter in the soil. Leaching studies in columns confirmed that thiamethoxam leached out of the soils readily, pointing out to a relatively high risk of ground water contamination with possible ecological impact when thiamethoxam is used in soils with low organic matter. In soil column studies, the soil with the lowest organic matter presents the greatest residue of neonicotinoids in the sub-surface (≤5 cm). In contrast the soil richer in organic matter presented most of the contamination deeper down in the column; a factor to be considered in the remediation from soil.

Multiple Known Mechanisms and a Possible Role of an Enhanced Immune System in Bt-Resistance in a Field Population of the Bollworm, Helicoverpa zea: Differences in Gene Expression with RNAseq.

Several different agricultural insect pests have developed field resistance to Bt (Bacillus thuringiensis) proteins (ex. Cry1Ac, Cry1F, etc.) expressed in crops, including corn and cotton. In the bollworm, Helicoverpa zea, resistance levels are increasing; recent reports in 2019 show up to 1000-fold levels of resistance to Cry1Ac, a major insecticidal protein in Bt-crops. A common method to analyze global differences in gene expression is RNA-seq. This technique was used to measure differences in global gene expression between a Bt-susceptible and Bt-resistant strain of the bollworm, where the differences in susceptibility to Cry1Ac insecticidal proteins were 100-fold. We found expected gene expression differences based on our current understanding of the Bt mode of action, including increased expression of proteases (trypsins and serine proteases) and reduced expression of Bt-interacting receptors (aminopeptidases and cadherins) in resistant bollworms. We also found additional expression differences for transcripts that were not previously investigated, i.e., transcripts from three immune pathways-Jak/STAT, Toll, and IMD. Immune pathway receptors (ex. PGRPs) and the IMD pathway demonstrated the highest differences in expression. Our analysis suggested that multiple mechanisms are involved in the development of Bt-resistance, including potentially unrecognized pathways.

Inflection point in climatic suitability of insect pest species in Europe suggests non-linear responses to climate change.

Climate change and globalization affect the suitable conditions for agricultural crops and insect pests, threatening future food security. It remains unknown whether shifts in species' climatic suitability will be linear or rather non-linear, with crop exposure to pests suddenly increasing when a critical temperature threshold is crossed. Moreover, uncertainty of forecasts can arise because of the modelling approach based either on species distribution data or on physiological measurements. Here, we compared the predictions of two modelling approaches (physiological models and species distribution models) for forecasting the potential distribution of agricultural insect pests in Europe. Despite conceptual differences, we found good agreement overall between the two approaches. We further identified a potential regime change in pest pressure along a temperature gradient. With both modelling approaches, we found an inflection point in the number of pest species with suitable climatic conditions around a minimum temperature of the coldest month of -3°C. Our results could help decision-makers anticipate the onset of rising pest pressure and provide support for intensifying surveillance measures, particularly in regions where temperatures are already beyond the inflection point.

Bioefficacy of Some Botanicals Against Gum Arabic Borer, Bruchus baudni Caill (Coleoptera: Bruchidae) on Stored Senegalia senegal Seeds

The use of bio-pesticides has proven to be successful approach in controlling agricultural insect pests. Study was conducted in the Laboratory of the Department of Crop Protection, Faculty of Agriculture, Bayero University, Kano to study the Biology of Bruchus baudni on treated Senegalia senegal seeds. Seed oils and leaf powders of K. senegalensis and M. oleifera at three concentrations each, a chemical insecticide (Aluminum phosphide as standard check) and a control were laid out in a Completely Randomized Design (CRD) and replicated three times. Data collected were oviposition, egg hatchability and developmental stages. The results indicated significant reduction in the number of eggs laid (1% and 1.38%) and hatchability (0.00% and 0.57%) on both seed oil and leaf powder treatments, respectively; however, the control recorded the highest eggs laid (99.9%) and number of emerged B. baudni (99.2%). The present findings showed that seeds and leaves of mahogany and moringa were effective as protectant against some of the development stages of B. baudni. Therefore, based on the present results, mahogany and moringa seeds and leaves could be explored to replace the synthetic insecticides in the management of B. baudni especially as components of integrated pest management strategy.

Serratia marcescens secretes proteases and chitinases with larvicidal activity against Anopheles dirus

Vector control, the most efficient tool to reduce mosquito-borne disease transmission, has been compromised by the rise of insecticide resistance. Recent studies suggest the potential of mosquito-associated microbiota as a source for new biocontrol agents or new insecticidal chemotypes. In this study, we identified a strain of Serratia marcescens that has larvicidal activity against Anopheles dirus, an important malaria vector in Southeast Asia. This bacterium secretes heat-labile larvicidal macromolecules when cultured under static condition at 25°C but not 37°C. Two major protein bands of approximately 55 kDa and 110 kDa were present in spent medium cultured at 25°C but not at 37°C. The Liquid Chromatography-Mass Spectrometry (LC-MS) analyses of these two protein bands identified several proteases and chitinases that were previously reported for insecticidal properties against agricultural insect pests. The treatment with protease and chitinase inhibitors led to a reduction in larvicidal activity, confirming that these two groups of enzymes are responsible for the macromolecule's toxicity. Taken together, our results suggest a potential use of these enzymes in the development of larvicidal agents against Anopheles mosquitoes.