Application Of Chemical Insecticides Research Articles

Viral diversity in the European spruce bark beetle Ips typographus as revealed through high-throughput sequencing

The European spruce bark beetle, Ips typographus is the economically most important biotic damaging agent of Norway spruce. Efforts to delimit beetle populations by trapping, application of chemical insecticides, or mechanically excluding the beetles from their breeding substrates are often expensive and mostly inadequate. The use of natural enemies and viruses is receiving increased research interest as a potential environmentally healthy approach to control pest insect populations, but practical biocontrol methods against I. typographus are still lacking. To learn more about putative enemies of this pest species, we used high-throughput sequencing to determine its viral community using beetles collected at a Finnish forest site. The analysis revealed a diverse community of RNA viruses associated with I. typographus, including novel viruses that could be affiliated with the classified families Benyviridae, Metaviridae, Narnaviridae, Partitiviridae, Phenuiviridae, Solemoviridae, Virgaviridae, Tombusviridae, and proposed family Spiciviridae, as well as unclassified “quenyaviruses”. Based on phylogenetic analysis, the viruses were distinct from, but resembled, unclassified viruses originating from other arthropods, and many of them were distantly related to previously described viruses. The possibility that the viruses could be hosted by other organisms than the beetle itself (associated fungi, nematodes and protozoa) was addressed by bioinformatic and phylogenetic analyses and is discussed.

Bruchid Infestation Was Associated With Agronomic Traits in Field-grown Faba Bean Genotypes

Bruchus rufimanus, a univoltine seed weevil (bruchid), can cause severe seed yield and quality losses in faba beans restricting crop profitability and expansion. Chemical insecticide applications have been reported of low effectiveness and thus, growing genotypes tolerant to bruchid has been suggested as an alternative. Ten faba bean (Viciafaba L.) accessions belonging to three varieties (var. major (seven accessions), var. minor (two accessions), var. equina (one accession)) were tested under field conditions for two growing seasons. Agronomic and seed traits were determined in an attempt to associate any tolerance to bruchid with easily-assessible, highly-heritable characters in order to be used as indirect selection criteria. The genotypes varied in bruchid tolerance (percentage of bruchid emergence holes (BD), percentage of endoparasitoid (Triaspis thoracica) emergence holes and bruchid infestation level (BI = BD + PD)), agronomic traits and seed properties. The dark-colored, small- and medium-seeded accessions (var. minor and var. equina), commonly used for feed, had the lowest BI (4.21–8.17%) ranging below the limit of 10% set as the highest acceptable for using faba beans as feed. Large-seeded accessions (var. major), which had light-colored seed coat (testa) with yellow hue, showed BI from 11.80% up to 24.54%, far-above the limit of 3% for seeds used as food. Apart from the seed size and color, susceptible genotypes had more seeds per pod, less pods and less branches per plant, possibly offering an easy access to females for laying more eggs on the limited number of pods, albeit the more space and food (higher protein content per seed) they offer to the developing larvae. Phenols and tannins in seeds, a putative chemical defense mechanism against bruchid, did not associate with the percentage of bruchid- or endoparasitoid-damaged seeds. Concluding, certain plant architectural traits and seed properties related to bruchid infestation in faba beans can be used as useful tools to select tolerant genotypes.

Effect of Entomopathogenic Fungi to Eggs and Nymphs Survival of Halyomorpha halys (Hemiptera: Pentatomidae) Under Laboratory Conditions.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is becoming a major pest of Greece's agricultural production, including tree fruit. Until now, the control of this pest has been based on conventional methods, with the application of chemical insecticides being the primary option. However, the wide distribution of H. halys, in combination with the large area of tree fruit production in Greece, raise the need for alternative control methods. In this study, we investigated the possibility of implementing microbial control agents for managing H. halys. Eggs and nymphs of H. halys were treated with 15 native entomopathogenic fungal isolates and their virulence was evaluated in the laboratory. After treatment, egg hatching time was recorded for 7days and ranged from 4.5 to 7.0days. Nymphal survival was recorded daily for 7days following application and ranged from 2.1 to 6.6days for second instar nymphs and 3.7 to 6.8days for fourth instar ones. Beauveria varroae isolate displayed the highest toxicity to all H. halys stages that were tested and could be considered a promising biocontrol agent of this insect. Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.οκ.

Isolation, characterization and docking analysis of insecticidal compound from Ocimum canum methanolic leaf extracts and its potential against three mosquito vectors

Vector management is an important challenge and burden to developing countries. Frequent and indiscriminate application of chemical insecticides for vector control has resulted in the development of resistance and undesirable effects on beneficial organisms. Hence an alternative approach is needed for the mosquito control programme. The present study investigated the insecticidal activity and spectral analysis of Ocimum canum methanol leaf extract against three mosquito species. One out of four fractions (F1-F4), the 4th fraction, revealed showed good insecticidal activity in larva and adult Cx. quinquefasciatus, Ae. aegypti and An. stephensi (0.114, 0.325 and 0.173 ppm) and (1.798, 1.061 and 0.871 ppm). The mortality was found to be dosage dependant. Spectral analysis of 1H NMR and 13C NMR indicates the presence of 6 protons at δH value of 7.45 (s) and 3 protons at δH value of 7.85 (s) ppm. FT-IR identified the possible band near the capping region at 3417.16 cm-1. LC-MS confirmed the eugenol compound with 99.79% purity at the molecular weight of 164. Further, eugenol docking analysis revealed high homology similarity with insect odorant binding protein 3OGN and AchE protein 2BG9. Overall, the result suggests that isolated eugenol compounds were found to be effective for the eco-friendly management of mosquito vectors. These findings could be useful for designing an efficient mosquitocidal compound in the future.

Empowerment of Farmer Group in Controlling Spodoptera frugiperda on Corn Using Entomopathogenic Fungi

Raden Farmer Group is one of the farmer groups in Pabuwaran, Purwokerto District, Banyumas Regency. This group faced the problem of encountering the attack of Spodoptera frugiperda on corn. This pest caused a detrimental loss in corn cultivation. The common control technique used to control this pest is by applying chemical insecticides. The use of this chemical insecticide causes negative effects on both the environment and human health. The offered solution to overcome this problem is technology transfer using entomopathogenic fungi, which is environmentally safe. Technology transfer was conducted through mentoring, education, and demonstration plots (demplots). Evaluation was carried out by pre-test and post-test for each activity to find out how well the partners understood the presented materials. The improvement in skills was measured by assessing the entomopathogenic fungi-based bioinsecticide product that was successfully made in the training activity by the partners, the decrease in S. frugiperda attack intensity, and the increase in yields in demplot. The evaluation results showed: (a) improvement of the partner’s knowledge and skills regarding S. frugiperda and its control technique using entomopathogenic fungi; (b) the results on demplot showed that the use of entomopathogenic fungi could replace the application of chemical insecticides to control S. frugiperda. (c) Farm analysis showed that the use of entomopathogenic fungi in corn cultivation was efficient and profitable for farmers.

USO DE INSETICIDAS BIOLÓGICOS NO CONTROLE DE INSETOS PRAGAS DAS CULTURAS DO SORGO E FEIJÃO

The project was developed at the IAC, in Votuporanga, São Paulo State, Brazil. The experimental design used was randomized blocks with four repetitions, using five treatments: sorghum culture: standard treatment (without insecticide application, T1); Colossus BT-2 (B. thugingiensis subsp. Kurstaki) and Comander (C. subtlesugae) at doses of 0.3 L ha-1 and 0.2 L ha-1, respectively (T2); 0.4 L ha-1 and 0.3 L ha-1, respectively (T3); 0.5 L ha-1 and 0.4 L ha-1, respectively (T4); application of chemical insecticides (T5); bean culture: standard treatment (without insecticide application, T1); Application of Ultron-S+A (S. spinosa) at doses of 0.2 L ha-1 (T2); 0.3 L ha-1 (T3); 0.4 L ha-1 (T4); application of chemical insecticides (T5). The plots were 5.0 x 5.0 m, totaling 25 m2. In sorghum culture was evaluated the incidence (%) of plants with the presence of caterpillars in the leaves; the incidence (%) of plants with caterpillars attack symptoms in the leaves; the incidence (%) of plants with the presence of aphids in the leaves; the incidence (%) of plants with symptoms of attack of aphids in the leaves; final stand ha-1 and grain yield ha-1. In bean culture was evaluated the incidence (%) of plants with the presence of caterpillars in the leaves; the incidence (%) of plants with symptoms of attack of caterpillars in the leaves; the incidence (%) of plants with the presence of thrips in the leaves; the incidence (%) of plants with thrips attack symptoms in the leaves; final stand ha-1 and grain yield ha-1.

Bacterial Pesticidal Protein Mpp51Aa1 Delivered via Transgenic Citrus Severely Impacts the Fecundity of Asian Citrus Psyllid, Diaphorina citri.

The Asian citrus psyllid (ACP) Diaphorina citri vectors the causative agent of citrus greening disease that has the capacity to decimate citrus production. As an alternative and more sustainable approach to manage D. citri than repeated application of chemical insecticides, we investigated the potential use of the bacteria-derived pesticidal protein, Mpp51Aa1, when delivered by transgenic Citrus sinensis cv. Valencia sweet orange or Citrus paradisi cv. Duncan grapefruit. Following confirmation of transcription and translation of mpp51aa1 by transgenic plants, no impact of Mpp51Aa1 expression was seen on D. citri host plant choice between transgenic and control Duncan grapefruit plants. A slight but significant drop in survival of adult psyllids fed on these transgenic plants was noted relative to those fed on control plants. In line with this result, damage to the gut epithelium consistent with that caused by pore-forming proteins was only observed in a minority of adult D. citri fed on the transgenic Duncan grapefruit. However, greater impacts were observed on nymphs than on adults, with a 40% drop in the survival of nymphs fed on transgenic Duncan grapefruit relative to those fed on control plants. For Valencia sweet orange, a 70% decrease in the number of eggs laid by adult D. citri on transgenic plants was noted relative to those on control plants, with a 90% drop in emergence of progeny. These impacts that contrast with those associated with other bacterial pesticidal proteins and the potential for use of Mpp51Aa1-expressing transgenic plants for suppression of D. citri populations are discussed. IMPORTANCE Pesticidal proteins derived from bacteria such as Bacillus thuringiensis are valuable tools for management of agricultural insect pests and provide a sustainable alternative to the application of chemical insecticides. However, relatively few bacterial pesticidal proteins have been used for suppression of hemipteran or sap-sucking insects such as the Asian citrus psyllid, Diaphorina citri. This insect is particularly important as the vector of the causative agent of citrus greening, or huanglongbing disease, which severely impacts global citrus production. In this study, we investigated the potential of transgenic citrus plants that produce the pesticidal protein Mpp51Aa1. While adult psyllid mortality on transgenic plants was modest, the reduced number of eggs laid by exposed adults and the decreased survival of progeny was such that psyllid populations dropped by more than 90%. These results provide valuable insight for potential deployment of Mpp51Aa1 in combination with other control agents for the management of D. citri.

Influence of ‘Candidatus Liberibacter asiaticus’ infection on the susceptibility of Asian citrus psyllid, Diaphorina citri to Bacillus thuringiensis pesticidal proteins, Mpp51Aa1 and Cry1Ba1

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae) transmits the Gram-negative bacterium ‘Candidatus Liberibacter asiaticus’ that causes citrus greening disease. While chemical control has been the main management strategy for limiting D. citri, the widespread usage of chemical sprays has decreased the susceptibility of D. citri to most insecticides. Pesticidal proteins produced by the bacterium Bacillus thuringiensis (Bt) are active against a wide variety of insects and provide a more sustainable approach to insect control. Herein, we investigated the impact of ‘Ca. L. asiaticus’ infection of D. citri on the toxicity of two Bt proteins (Mpp51Aa1 and Cry1Ba1). Proteins were delivered to healthy and ‘Ca. L. asiaticus’-infected D. citri via topical feeding application. The LC50 values of Mpp51Aa1 and Cry1Ba1 were calculated for both nymphs and adults. Additionally, we evaluated the effect of each protein on the survival probability and life span of healthy and ‘Ca. L. asiaticus’-infected D. citri. The LC50 values indicated that adults and nymphs were more susceptible to Mpp51Aa1 than to Cry1Ba1 in both healthy and ‘Ca. L. asiaticus’-infected D. citri. ‘Ca. L. asiaticus’-infected adults and nymphs were more susceptible to Mpp51Aa1 and Cry1Ba1 than healthy insects, and nymphs were more susceptible to Mpp51Aa1 and Cry1Ba1 than adults. Moreover, we found that Mpp51Aa1 had a greater impact than Cry1Ba1 on the survival and lifespan of adults, and ‘Ca. L. asiaticus’-infected insects were more affected by these pesticidal proteins than healthy adults. These results have important implications for the use of pesticidal proteins in D. citri management in Florida and elsewhere given the widespread presence of ‘Ca. L. asiaticus’ in the D. citri population. In this era of eco-friendly control strategies, Bt-derived pesticidal proteins provide a promising avenue to reducing the application of chemical insecticides for D. citri management.

Bio-efficacy of Chemical Insecticides against Major Insect Pests of Mustard Applied through Seed Treatment

Seed treatment application of chemical insecticides is getting popularity in the management of insect-pest population. The present investigation was conducted to study the bio-efficacy of different chemical insecticides, widely used against major insect-pest of mustard crop. A mustard variety Bio-902 was sown in twenty-seven plots of 2× 2 m2 at the agronomy farm of Sri Karan Narendra College of Agriculture, Jobner, India during the Rabi season of 2020-21. A total of nine treatments including an untreated control group with three replications were investigated in a randomized block design (RBD). The data was recorded for aphid population and seed yield in each treatment. The treatments including Imidacloprid 40% + Fipronil 40% (10 g/kg seed) was found significantly effective followed by Imidacloprid (10 g/kg seed), Clothianidin (10 g/kg seed), Thiamethoxam (10 g/kg seed), Imidacloprid 40% + Fipronil 40% (5 g/kg seed), Imidacloprid (5 g/kg seed), Clothianidin (5 g/kg seed) and Thiamethoxam (5 g/kg seed). The ranking of treatments based on seed yield in mustard was found to be similar to the trend observed in the aphid population for different treatments. Seed treatment helps protect the seed and emerging plant from insects until they become more resilient. Method of seed treatment and doses of pesticides to be used in seed treatment are deciding factor for bio efficacy of pesticides.

Control capacity of the LPSc 1067 strain of Beauveria bassiana (Ascomycota: Hypocreales) on different species of grasshoppers (Orthoptera: Acrididae: Melanoplinae), agricultural pests in Argentina

Grasshoppers affect agriculture worldwide, causing serious economic damage. Currently, the application of chemical insecticides against grasshoppers is the only effective strategy, even considering the significant environmental concern. This study aimed to test the entomopathogenic fungi Beauveria bassiana (LPSc 1067) as biocontrol agent on six harmful grasshopper species in Argentina. Significant differences were observed (DF= 5; F= 9.93; P<0.0001) when considering B. bassiana pathogenicity on third-instar nymphs of the different grasshopper species. The highest mortality (100%) was registered on Trimerotropis pallidipennis and Dichroplus maculipennis nymphs while the lowest mortality (48.6 ±3.5%) was observed on Scotussa lemniscata nymphs. The lowest mean survival time (MST) was recorded for T. pallidipennis (3.5 ±0.15 days) and the highest MST was observed on Dichroplus pratensis nymphs (7.48 ±0.28 days). Results suggest that B. bassiana LPSc 1067 may constitute an excellent candidate to be further studied as biological control agent of T. pallidipennis and D. maculipennis. Highlights: Melanoplinae grasshoppers include several species considered plagues. Entomopathogenic fungi as biocontrol agents are considered excellent alternatives to chemical control. The efficacy of bassiana (LPSc 1067) on six grasshopper species of Argentina. The isolate LPSc 1067 could be considered a biological controller pallidipennis and D. maculipennis.

Sustainable Management for Spiralling Whitefly, Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae) Infesting Guava and Its Effects on the Natural Enemies’ Complex

The spiralling whitefly, Aleurodicus dispersus (Hemiptera: Aleyrodidae), is one of the most notorious insect pests among tropical fruits and vegetables. A common pest management technique is the application of chemical insecticides. However, this has led to environmental degradation, natural enemy reduction, development of pesticide resistance and increased cost of production. This study, therefore, evaluated the efficacy of a sustainable and eco-friendly management strategy against the spiralling whitefly infesting guava (Psidium guajava L). The experiment was carried out with seven treatments replicated five times following the randomized complete block design. The treatments were negative control (T1), 0.8% soybean oil (T2), 1.6% liquid dishwashing (T3), 1.6% neem oil (T4), 0.4% soybean oil + 0.8% liquid dishwashing (T5), 0.8% neem oil + 0.8% liquid dishwashing (T6) and chemical control (Thiamethoxam 25 WG at 2g/L-1) (T7). Results showed that 1.6% liquid dishwashing was superior among treatments against the 1st, 2nd and 3rd nymphal instars with an average mortality of 84.28, 85.22 and 81.81%, respectively. Application of 0.8% soybean oil showed the highest efficacy against the eggs, 4th instar and adult population with an average mortality of 75.50, 81.36 and 93.50%, respectively. Application of these treatments showed no adverse effects on the natural enemies’ complex associated with guava. Integration of other eco-friendly pest management strategies against the invasive spiralling whitefly is recommended for future research.

Cry1Ba1-mediated toxicity of transgenic Bergera koenigii and Citrus sinensis to the Asian citrus psyllid Diaphorina citri.

The Asian citrus psyllid, Diaphorina citri, vectors the bacterial causative agent of citrus greening disease, which has severely impacted citrus production on a global scale. As the current repeated application of chemical insecticides is unsustainable for management of this insect and subsequent protection of groves, we investigated the potential use of the bacteria-derived pesticidal protein, Cry1Ba1, when delivered via transgenic citrus plants. Having demonstrated transformation of the Indian curry leaf tree, Bergera koenigii, for Cry1Ba1 expression for use as a trap plant, we produced transgenic plants of Duncan grapefruit, Citrus paridisi, Valencia sweet orange, Citrus sinensis, and Carrizo citrange, C. sinensis x Poncirus trifoliata, for expression of Cry1Ba1. The presence of the cry1ba1 gene, and cry1ba1 transcription were confirmed. Western blot detection of Cry1Ba1 was confirmed in most cases. When compared to those from wild-type plants, leaf discs from transgenic Duncan and Valencia expressing Cry1Ba1 exhibited a "delayed senescence" phenotype, similar to observations made for transgenic B. koenigii. In bioassays, significant reductions in the survival of adult psyllids were noted on transgenic B. koenigii and Valencia sweet orange plants expressing Cry1Ba1, but not on transgenic Duncan grapefruit or Carrizo citrange. In contrast to psyllids fed on wild type plants, the gut epithelium of psyllids fed on transgenic plants was damaged, consistent with the mode of action of Cry1Ba1. These results indicate that the transgenic expression of a bacterial pesticidal protein in B. koenigii and Valencia sweet orange offers a viable option for management of D. citri, that may contribute to solutions that counter citrus greening disease.

Wood Vinegar as an Alternative Insecticide in Controlling Rice Weevil, Sitophylus oryzae (Coleoptera: Curculionidae)

Rice production faces many challenges including damages due to pest infestation in storage after harvest. Stored rice grains are often under threat and damage from pests such as rice weevil which resulted in reduction of the quality and quantity. Application of chemical insecticides helps to control this pest, however, it gives negative impacts to the environment and human health. Application of plant-based insecticides including the use of wood vinegar can become an alternative to the conventional method. This work describes the effectiveness of wood vinegar as bioinsecticide to inhibit the rice weevil’s activity by assessing the repellency, mortality and antifeedant activity at different concentration of 50, 100, 150 and 200 rpm. Wood vinegar showed high repellency of 98.3% towards rice weevils at 200 ppm after 5 hours of exposure times. Increased in concentration affects in increased mortality with highest number of 97% recorded at 200 ppm. The lethal concentration (LC) of wood vinegar was calculated to be 77.62 ppm. Antifeedant activity resulted in reduction of weight loss in stored rice with lowest reduction of 2% at 200 ppm. This promising result reflects the ability of wood vinegar as insecticidal agents in management and control of stored-grain pest.

Cotton leafroll dwarf disease: An enigmatic viral disease in cotton.

Cotton leafroll dwarf virus (CLRDV) is a member of the genus Polerovirus, family Solemoviridae. Geographical Distribution: CLRDV is present in most cotton-producing regions worldwide, prominently in North and South America. The virion is a nonenveloped icosahedron with T = 3 icosahedral lattice symmetry that has a diameter of 26-34 nm and comprises 180 molecules of the capsid protein. The CsCl buoyant density of the virion is 1.39-1.42 g/cm3 and S20w is 115-127S. Genome: CLRDV shares genomic features with other poleroviruses; its genome consists of monopartite, single-stranded, positive-sense RNA, is approximately 5.7-5.8 kb in length, and is composed of seven open reading frames (ORFs) with an intergenic region between ORF2 and ORF3a. CLRDV is transmitted efficiently by the cotton aphid (Aphis gossypii Glover) in a circulative and nonpropagative manner. Host: CLRDV has a limited host range. Cotton is the primary host, and it has also been detected in different weeds in and around commercial cotton fields in Georgia, USA. Cotton plants infected early in the growth stage exhibit reddening or bronzing of foliage, maroon stems and petioles, and drooping. Plants infected in later growth stages exhibit intense green foliage with leaf rugosity, moderate to severe stunting, shortened internodes, and increased boll shedding/abortion, resulting in poor boll retention. These symptoms are variable and are probably influenced by the time of infection, plant growth stage, varieties, soil health, and geographical location. CLRDV is also often detected in symptomless plants. Vector management with the application of chemical insecticides is ineffective. Some host plant varieties grown in South America are resistant, but all varieties grown in the United States are susceptible. Integrated disease management strategies, including weed management and removal of volunteer stalks, could reduce the abundance of virus inoculum in the field.

Mortality of the cotton boll weevil in drip and sprinkler irrigated cotton crops.

The cotton boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is a key cotton crop pest in Brazil. Adverse climatic factors, such as high temperatures and low soil moisture, dehydrate oviposited cotton squares (bud flowers) on the ground and cause high mortality of its offspring within these plant structures. The objective of this research was to evaluate the mortality of the cotton boll weevil in drip and sprinkler irrigated cotton crops. The experimental design was in randomized blocks with two treatments: drip (T1) and sprinkler (T2, control) irrigated cotton crops with sixteen replications. Each parcel had one emergence cage, installed between two cotton rows per irrigation system, with 37 cotton squares with opened oviposition punctures and yellowish bracts, to capture adult cotton boll weevils. The average number of boll weevils that emerged from the cotton squares and the causes of mortality at different development stages were determined per treatment. Third-generation life tables of the boll weevil were prepared using the natural mortality data in drip and sprinkler irrigation treatments and plus actual, apparent and indispensable mortality rates and the lethality of each mortality cause. We conclude that the application of water directly to the root zone of the plants in a targeted manner, using the drip irrigation system, can cause high mortality of the cotton boll weevil immature stages inside cotton squares fallen on the ground. This is because the cotton squares fallen on the drier and hotter soil between the rows of drip-irrigated cotton dehydrates causing the boll weevils to die. This is important because it can reduce its population density of the pest and, consequently, the number of applications of chemical insecticides for its control. Thus, contributing to increase the viability of cotton production, mainly in areas of the Brazilian semiarid region where the cotton is cultivated in organic system.

Entomopathogenic fungi of Fusarium

Uzrokujući direktne ili indirektne štete i prenoseći biljne bolesti, kukci stvaraju višestruke gubitke u poljoprivrednoj proizvodnji, što se očituje smanjenom kvalitetom i prinosom usjeva. Uz primjenu kemijskih insekticida, koji su najčešći u konvencionalnoj poljoprivredi, nastoje se pronaći odgovarajući alternativni načini suzbijanja štetnika koji su okolišno prihvatljivi. Jedan je od takvih načina biološka kontrola kukaca entomopatogenim gljivama, za koje je utvrđena iznimno visoka učinkovitost u suzbijanju mnogih vrsta kukaca. Cilj rada bio je navesti mogućnosti suzbijanja kukaca entomopatogenim gljivama roda Fusarium te prikazati njihov potencijal primjene, od tretiranja sjemena, tretiranja kukaca do tretiranja skladišta. Brojne vrste roda Fusarium pokazale su visoku učinkovitost suzbijanja kukaca u svim fazama njihovog razvoja te su pogodne za daljnja istraživanja.

ECry1Gb.1Ig, A Novel Chimeric Cry Protein with High Efficacy against Multiple Fall Armyworm (Spodoptera frugiperda) Strains Resistant to Different GM Traits.

Spodoptera frugiperda (fall armyworm, FAW) is one of the most devastating insect pests to corn and soybean production in the Americas and is rapidly expanding its range worldwide. It is known to be hard to control either by chemical insecticide applications or by GM. Although the use of GM traits can be an effective way to control this pest, it is very rare to find native insecticidal proteins that provide the necessary level of FAW control in crop fields where FAW pressure and damage are high. Insecticidal Cry proteins sourced from Bacillus thuringiensis have been heavily utilized in the development of crops with GM traits; however, it is increasingly difficult to identify Cry proteins with unique modes of action. Protein engineering via a phylogenetically guided Cry protein domain swapping approach enabled us to discover novel chimeric Cry proteins engineered from inactive parent sequences. Some of these chimeras show excellent efficacy against key biotypes of FAW from Brazil and North America. In this study, we characterized a Cry-based chimera eCry1Gb.1Ig that is a very potent FAW toxin. eCry1Gb.1Ig showed high efficacy against multiple FAW strains that are resistant to various traits, including Cry1Fa, Vip3Aa and Cry1A.105/Cry2Ab. These results clearly indicate that the FAW strains resistant to Cry1Fa, Vip3Aa or Cry1A.105/Cry2Ab demonstrate no cross-resistance to eCry1Gb.1Ig and strongly suggest that eCry1Gb.1Ig acts through a novel mode of action compared to the existing traits. In addition to its FAW activity, eCry1Gb.1Ig has also been shown to control Chrysodeixis includens (soybean looper, SBL) and Anticarsia gemmatalis (velvetbean caterpillar, VBC), which are significant pests of soybean. When eCry1Gb.1Ig was introduced into corn and soybean crops, transgenic events showed strong efficacy against FAW, SBL and VBC, but no adverse plant phenotypes. This suggests that the in planta expression of the eCry1Gb.1Ig protein does not compromise plant growth or reproduction and can protect plants from FAW-related damage. Therefore, this valuable discovery will provide a differentiating FAW control trait that will give growers another tool to help them reduce yield loss due to FAW.

Impact of covert infections with an RNA virus on the susceptibility of Spodoptera exigua to natural enemies

Integrated Pest Management (IPM) programs are alternatives to classical pest control through the application of chemical insecticides. IPM goal is to maintain pest populations below economically injurious levels minimizing the use of chemical insecticides. In recent years, research on insect viromes has led to the discovery of many novel viral pathogens in insect pests, some of them producing covert infections that do not cause evident symptoms. However, the impact that these viruses have on the action of natural enemies employed in IPM programs is still unknown. Spodoptera exigua iflavirus 1 (SeIV1) is an RNA virus commonly found in field populations of Spodoptera exigua. In this work, we have analysed the possible impact of those viral infections on the activity of different natural enemies used for the control of this pest. Specifically, we have studied the effects of SeIV1 on susceptibility to entomopathogenic nematodes, fungi, bacteria, and parasitoids. Infections with SeIV1 showed to be compatible with the nematode Steinernema carpocapsae as the infection did not affect the susceptibility or production of new juveniles. Moreover, they are also compatible with the fungus Metarhizium brunneum as the mortality of S. exigua larvae was not affected by the viral infection. Interestingly, infections with SeIV1 increase the susceptibility to Bacillus thuringiensis formulation and increase the mortality caused by the parasitism of Hyposoter didymator. In summary, our results show that the four natural enemies tested are not negatively affected by SeIV1 and their action remains similar or enhanced by the covert infections with this iflavirus.

Impact of Imidacloprid Resistance on the Demographic Traits and Expressions of Associated Genes in Aphis gossypii Glover.

Imidacloprid is one of the most widely used neonicotinoid insecticides to control sap-sucking insect pests, including Aphis gossypii. The intensive application of chemical insecticides to A. gossypii led to the development of resistance against several insecticides, including imidacloprid. Therefore, it is crucial to understand the association between imidacloprid resistance and the fitness of A. gossypii to limit the spread of the resistant population under field contexts. In this study, we used the age-stage, two-sex life table method to comprehensively investigate the fitness of imidacloprid resistant (ImR) and susceptible strains (SS) of melon aphids. Results showed that ImR aphids have prolonged developmental stages and decreased longevity, fecundity, and reproductive days. The key demographic parameters (r, λ, and R0) were significantly reduced in ImR strain compared to SS aphids. Additionally, the molecular mechanism for fitness costs was investigated by comparing the expression profile of juvenile hormone-binding protein (JHBP), juvenile hormone epoxide hydrolase (JHEH), juvenile hormone acid O-methyltransferase (JHAMT), Vitellogenin (Vg), ecdysone receptor (EcR), and ultraspiracle protein (USP) supposed to be associated with development and reproduction in insects. The results of RT-qPCR showed that EcR, JHBP, JHAMT, JHEH, and Vg genes were downregulated, while USP was statistically the same in ImR A. gossypii compared to the SS strain. Together, these results provide in-depth information about the occurrence and magnitude of fitness costs against imidacloprid resistance that could help manage the evolution and spread of A. gossypii resistance in field populations.

Field Evolution of Insecticide Resistance against Sogatella furcifera (Horváth) in Central China, 2011–2021

The white-backed planthopper Sogatella furcifera (Horváth) is an important pest on rice plants throughout Asia. The application of chemical insecticides is still the main approach to suppressing the field population of S. furcifera. However, misuse of chemical insecticides has promoted the development of insecticide resistance in this insect pest. Thus, in the present study, dose responses of 58 field populations of S. furcifera to 7 insecticides were analyzed by rice-stem dipping from 2011 to 2021 in Central China. The results indicated that field populations of S. furcifera showed moderate levels of resistance to nitenpyram (RR = 1.7–17.8-fold), thiamethoxam (RR = 1.4–25.8-fold), dinotefuran (RR = 1.5–25.3-fold), clothianidin (RR = 2.1–12.5-fold), chlorpyrifos (RR = 1.1–56.6-fold), etofenprox (RR = 1.1–14.8-fold) and isoprocarb (RR = 1.4–11.5-fold). The results presented here will be beneficial to improve our ability to identify and predict insecticide resistance, make better control recommendations and prevent further insecticide resistance development.