Neonate Larvae Research Articles

Asaia spp. Accelerate development of the yellow fever mosquito, Aedes aegypti, via interactions with the vertically transmitted larval microbiome.

A wide range of vector control programs rely on the efficient production and release of male mosquito. Asaia bacteria are described as potential symbionts of several mosquito species but their relationship with Aedes aegypti has never been rigorously tested. Here we aimed to quantify the benefits of three Asaia species on host development in Ae. aegypti, and the ability of these bacteria to form a stable symbiotic association with growing larvae. In order to disentangle direct and indirect effects of Asaia inoculation on host development, experiments used insects with an intact microbiome and those reared in near-aseptic conditions, while we characterized bacterial communities and Asaia densities with culture dependent and independent methods (16S rRNA amplicon sequencing). Neonate larvae were inoculated with Asaia spp. for 24 hours, or left as uninoculated controls, all were reared on sterile food. Aseptic larvae were produced by surface sterilization of eggs. Although all Asaia were transient members of the gut community, two species accelerated larval development relative to controls. The two mutualistic species had lasting impacts on the larval microbiome, largely by altering the relative abundance of dominant bacteria, namely Klebsiella and Pseudomonas. Axenic larvae were dominated by Asaia when inoculated with this species but showed slower development than conventionally reared insects, indicating that Asaia alone could not restore normal development. Our results reveal Asaia as a poor mutualist for Ae. aegypti, but with a species-specific positive effect on improving host performance mediated by interactions with other bacteria.

Resistance of Bt and Non-Bt Soybean Cultivars Adapted to Novel Growing Regions of Brazil to Chrysodeixis includens and Spodoptera frugiperda.

Soybean is a highly valuable commodity crop for Brazil's economy. However, it faces significant threats from the attack of a complex of lepidopteran pests, particularly Chrysodeixis includens (Walker) and Spodoptera frugiperda (J. E. Smith). These pests have been managed primarily using transgenic Bt soybeans, but limited knowledge exists about the resistance levels of Bt and non-Bt cultivars adapted to novel soybean-growing areas in Brazil, such as the Minas Gerais state. This study evaluated the resistance levels of Bt and non-Bt soybean cultivars to C. includens and S. frugiperda, and whether the Bt cultivars can differentially affect these pests across larval stages. No-choice bioassays were conducted using Bt (NS6010 IPRO and P97R50 IPRO) and non-Bt soybeans (UFLA 6301 RR, P96R90 RR, and ANsc 80111 RR) at V4-stage in the laboratory with neonate (24 h) and third-instar larvae. Larvae were fed leaf discs in Petri dishes, recording the mortality, leaf consumption, and weight gain after 7 days. There was high mortality of C. includens neonates on the Bt cultivars, but this trend was not observed for older larvae. For S. frugiperda neonates, there was high mortality on the Bt cultivar NS 6010 IPRO and non-Bt cultivar UFLA 6301 RR, but only the former was effective for older larvae. Although the Bt cultivars did not kill the third instars, antinutritional effects were found, such that leaf tissue consumed was not converted to larval weight gain. These findings are important for defining regional strategies of integrated and resistance management of C. includens and S. frugiperda in expanding regions of soybean cultivation in Brazil.

A degree‐hour phenological model to forecast the first invasion of Sesamia cretica (Lepidoptera: Noctuidae)

AbstractCorn stem borer, Sesamia cretica Lederer, is an important pest of corn and sugarcane worldwide. The validation of a linear and some selected nonlinear models in semi‐field and field conditions regarding the development time of the Varamin and Rey populations of S. cretica was performed. Our previously published laboratory data on the development rate and thermal constant of the pest for both populations were used as baseline information. The results showed that to construct a forecasting model, the lower temperature threshold of the Ikemoto model and estimated thermal constant of semi‐field or field conditions could provide a more accurate model. In the management of corn stem borer, when the thermal constant of the environment reached 44874.45 DH and 51,644 degree‐hour (DH) for the populations of Varamin and Rey, respectively, in the second generation on corn, which coincides with the peak of eggs, the necessary measures for inhibition should be prepared. Pest control was recommended when it reached 45857.01 DH and 52692.56 DH in Varamin and Rey, respectively, which coincides with the emergence of neonate larvae. Using these results leads to more successful pest management and saving time and financial resources.

Toxicity of Bt Protein on Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) Fed With Corn Leaves in Paraguay

The fall armyworm Spodoptera frugiperda is the most destructive pest in corn cultivation in Paraguay with yield losses of 20 to 70%. The adoption of genetically modified crops (GMO) is a valid technique for managing this pest. The objective of this investigation was to evaluate the toxicity among Bt events used locally; determining mortality and important biological parameters. The S. frugiperda population previously collected from the field was raised under laboratory conditions fed with leaves from events MIR162TM (Vip3A19), VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and a treatment with non-maize. Bt BR106TM. The mortality of 120 larvae was evaluated for each treatment and the viability until the adult stage of those larvae that managed to survive the different treatments was observed. A high toxicity effect was verified with 100% mortality of neonatal larvae fed with the MIR162TM (Vip3A19) event; as for the other events, 86% and 61% VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), and PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) respectively; with 13% mortality for the non-Bt control variety BR106TM. The oviposition period, viability and number of eggs laid in adults surviving the PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb) events were reduced, affecting the fecundity of the surviving insect population.

Toxicity of Bt Protein on Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) Fed With Corn Leaves in Paraguay

The fall armyworm Spodoptera frugiperda is the most destructive pest in corn cultivation in Paraguay with yield losses of 20 to 70%. The adoption of genetically modified crops (GMO) is a valid technique for managing this pest. The objective of this investigation was to evaluate the toxicity among Bt events used locally; determining mortality and important biological parameters. The S. frugiperda population previously collected from the field was raised under laboratory conditions fed with leaves from events MIR162TM (Vip3A19), VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and a treatment with non-maize. Bt BR106TM. The mortality of 120 larvae was evaluated for each treatment and the viability until the adult stage of those larvae that managed to survive the different treatments was observed. A high toxicity effect was verified with 100% mortality of neonatal larvae fed with the MIR162TM (Vip3A19) event; as for the other events, 86% and 61% VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb), and PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) respectively; with 13% mortality for the non-Bt control variety BR106TM. The oviposition period, viability and number of eggs laid in adults surviving the PowerCoreTM (Cry1A105, Cry1F, Cry2Ab2) and VT3ProTM (Cry1A105, Cry2Ab2, Cry3Bb) events were reduced, affecting the fecundity of the surviving insect population.

The push-pull intercrop Desmodium does not repel, but intercepts and kills pests.

Over two decades ago, an intercropping strategy was developed that received critical acclaim for synergizing food security with ecosystem resilience in smallholder farming. The push-pull strategy reportedly suppresses lepidopteran pests in maize through a combination of a repellent intercrop (push), commonly Desmodium spp., and an attractive, border crop (pull). Key in the system is the intercrop's constitutive release of volatile terpenoids that repel herbivores. However, the earlier described volatile terpenoids were not detectable in the headspace of Desmodium, and only minimally upon herbivory. This was independent of soil type, microbiome composition, and whether collections were made in the laboratory or in the field. Furthermore, in oviposition choice tests in a wind tunnel, maize with or without an odor background of Desmodium was equally attractive for the invasive pest Spodoptera frugiperda. In search of an alternative mechanism, we found that neonate larvae strongly preferred Desmodium over maize. However, their development stagnated and no larva survived. In addition, older larvae were frequently seen impaled and immobilized by the dense network of silica-fortified, non-glandular trichomes. Thus, our data suggest that Desmodium may act through intercepting and decimating dispersing larval offspring rather than adult deterrence. As a hallmark of sustainable pest control, maize-Desmodium push-pull intercropping has inspired countless efforts to emulate stimulo-deterrent diversion in other cropping systems. However, detailed knowledge of the actual mechanisms is required to rationally improve the strategy, and translate the concept to other cropping systems.

Pest categorisation of Garella musculana.

The European Commission requested the EFSA Panel on Plant Health to conduct a pest categorisation of Garella musculana (Erschov) (Lepidoptera: Nolidae), following a commodity risk assessment of Juglans regia plants for planting from Türkiye, in which G. musculana was identified as a pest of possible concern to the European Union (EU). Commonly known as the Asian walnut moth, this pest is native to Central Asia and develops on shoots, buds and fruits of Juglans species such as the English walnut, J. regia and the black walnut, J. nigra. Other reported host plants, such as Prunus dulcis and Populus spp., still require confirmation. The pest was first recorded in the EU (Bulgaria) in 2016 and was then reported in Romania in 2018 and Italy in 2021. This moth completes from one to four generations per year depending on environmental conditions (from valley to mountain forests and orchards up to an altitude of 2100 m). Eggs are laid in groups of 2-3 on young nuts or on buds of 1-year-old shoots. Neonate larvae usually enter the young nut through the peduncle. After fully exploiting one nut, the larva continues feeding in another one. Development takes 25-40 days. Larvae of the autumn generation do not enter the nuts, and so feed only in the pericarp. Larvae also often feed inside 1-year-old shoots or leaf axils. Larvae develop within the host but exit to pupate under loose bark or in deep cracks of bark. The pest overwinters at the larval or pupal stages. Plants for planting, cut branches and infested nuts provide pathways for entry. Climatic conditions and availability of host plants in southern and central EU MSs have allowed this species to establish and spread in Bulgaria, Romania and Italy. Adults can fly and the pest could spread naturally within the EU. Impact on Juglans spp. cultivated for fruit, timber and ornamental purposes is anticipated. Phytosanitary measures are available to reduce the likelihood of entry and further spread of G. musculana. This species meets the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest.

Impact of Bt corn expressing Bacillus thuringiensis Berliner insecticidal proteins on the growth and survival of Spodoptera frugiperda larvae in Colombia.

Bioassays were conducted under controlled conditions to determine the response of Spodoptera frugiperda (J. E. Smith) larvae fed with corn materials expressing Bacillus thuringiensis (Bt) insecticidal endotoxins: (1) VT Double Pro® (VT2P) expressing Cry1A.105-Cry2Ab2 proteins and (2) VT Triple Pro® (VT3P) expressing Cry1A.105-Cry2Ab2-Cry3Bb1 proteins. The parameters assessed were: (i) mortality rate, and (ii) growth inhibition (GI) with respect to the control. To conduct this study, larvae were collected from commercial non-Bt corn fields, in four agricultural sub-regions in Colombia, between 2018 and 2020. Fifty-two populations were assessed from the field and neonate larvae from each of the populations were used for the bioassays. The study found that mortality rates in the regions for larvae fed with VT2P corn ranged from 95.1 to 100.0%, with a growth inhibition (%GI) higher than 76.0%. Similarly, mortality rate for larvae fed with VT3P corn were between 91.4 and 100.0%, with a %GI above 74.0%. The population collected in Agua Blanca (Espinal, Tolima; Colombia) in 2020, showed the lowest mortality rate of 53.2% and a %GI of 73.5%, with respect to the control. The population that exhibited the lowest %GI was collected in 2018 in Agua Blanca (Espinal, Tolima, Colombia) with a 30.2%, growth inhibition, with respect to the control. In recent years, the use of plant tissue to monitor susceptibility to fall armyworm has proven to be useful in the resistance management program for corn in Colombia determining that the FAW populations are still susceptible to Bt proteins contained in VT2P and VT3P.

Chemical composition and toxicity of Moroccan mentha spicata and Artemisia absinthium essential oils against Pthorimaea operculella, the potato moth

The current methods employed to mitigate losses caused by Phthorimaea operculella primarily rely on the application of synthetic insecticides. We have utilised essential oils of Mentha spicata L. and Artemisia absinthium against Phthorimaea operculella. The essential oils were obtained using hydrodistillation and analysed via gas chromatography–mass spectrometry. Mentha spicata essential oil contained D-limonene (25.12%) and D-carvone (7.47%) while the essential oil of Artemisia absinthium was rich of 3,3,5-trimethylcyclohexene (27.93%) and camphor (22.50%). Five concentrations (0, 1, 2, 4, and 8 µL/L of air) were applied to the four phases of P. operculella, neonate larvae, nymphs, eggs and adults. The results of the biological tests showed that spearmint oil was more toxic than wormwood oil, particularly at the adult and Chrysalide stages. Essential oils could be considered good alternatives to chemical pesticides for the protection of potato crops.

Phytochemical characterisation and toxicity effect of Tithonia diversifolia (Hemls.) A. Gray leaf extract on fall army worm Spodoptera frugiperda (JE Smith) larvae.

To mitigate the losses due to fall armyworm (FAW) infestation in maize, chemical pesticides had been the first choice and widely used as an emergency response. However, it comes with attendant health effect. This necessitates the development of plant based effective and safer pesticides. This research investigate response of fall armyworm larvae when they are exposed to crude and partially purified Tithonia diversifolia leaf extract. Chemical constituent of the extract was identified using NIST08.LIB library spectra provided by the software on a GC-MS system and FTIR analysis was done using KBr pellet technique with a resolution and scanning speed of 4 cm-1 and 2 mm/s. Dose dependent toxicity assay of T.diversifolia extracts on FAW at different growth stages under controlled environment in laboratory, followed by its effect under phytotron were examined against control and azadirachtin from neem. The GC-MS of the butanol eluent revealed 20 compounds out of which the major ones being beta-d-glucopyranoside, methyl (15.225 %) palmitic acid, TMS derivative (10.98 %) and hexadecanoic acid, 2-[(trimethylsily)oxy]-, methyl ester (8.75 %). The FT-IR spectroscopic analysis of the butanol eluent of T.diversifolia leaf extract revealed the presence of alcohols, phenols, aldehydes, ketones, alkanes and primary amines. The butanol eluent and crude extract caused 96 % mortality at neonate and first instar FAW larvae. The toxic and repellant effects revealed by diet bioassay and phytotron experiment respectively suggest that butanol eluent of T.diversifolia leaf extract could be a good and effective target for biopesticide production against FAW.

Capnodis tenebrionis (Coleoptera: Buprestidae), an important pest of stone fruits in the Mediterranean basin: current management strategies and prospects for integrated pest management

Abstract Capnodis tenebrionis (Linné) is a devastating pest of stone fruits (Prunus spp.) in the Mediterranean region. The endophytic root-boring larvae cause the main damage and can kill a large tree within 2 years. For several decades, with the absence of an effective biological control strategy, the management of this pest has mainly relied on the use of nonselective insecticides. These insecticides are applied either as a foliar spray targeting adults or as a soil treatment targeting neonate larvae. The search for alternative management options has increased since 2000 as a result of reduced efficacy of chemical control, decreased number of available insecticides, and the need for control measures suitable for organic stone fruit production. The main focus was on entomopathogenic nematodes and fungi. Several isolates/strains of these pathogens were found to be effective against larvae and adults of C. tenebrionis under laboratory and semi-field conditions. In this article, we review the current management options of C. tenebrionis, including chemical, biological, resilient rootstock, and cultural options. The prospects for developing an integrated management approach for this pest are also discussed.

Development of a soybean leaf disc assay for determining oral insecticidal activity in the lepidopteran agricultural pest Helicoverpa armigera

Pest insects pose a heavy burden on global agricultural industries with small molecule insecticides being predominantly used for their control. Unwanted side effects and resistance development plagues most small molecule insecticides such as the neonicotinoids, which have been reported to be harmful to honeybees. Bioinsecticides like Bacillus thuringiensis (Bt) toxins can be used as environmentally-friendly alternatives. Arachnid venoms comprise another promising source of bioinsecticides, containing a multitude of selective and potent insecticidal toxins. Unfortunately, no standardised insect models are currently available to assess the suitability of insecticidal agents under laboratory conditions. Thus, we aimed to develop a laboratory model that closely mimics field conditions by employing a leaf disk assay (LDA) for oral application of insecticidal agents in a bioassay tray format. Neonate larvae of the cotton bollworm (Helicoverpa armigera) were fed with soybean (Glycine max) leaves that were treated with different insecticidal agents. We observed dose-dependent insecticidal effects for Bt toxin and the neonicotinoid insecticide imidacloprid, with imidacloprid exhibiting a faster response. Furthermore, we identified several insecticidal arachnid venoms that were active when co-applied with sub-lethal doses of Bt toxin. We propose the H. armigera LDA as a suitable tool for assessing the insecticidal effects of insecticidal agents against lepidopterans.

Bacillus thuringiensis Bt_UNVM-84, a Novel Strain Showing Insecticidal Activity against Anthonomus grandis Boheman (Coleoptera: Curculionidae).

Bacillus thuringiensis is a Gram-positive bacterium known for its insecticidal proteins effective against various insect pests. However, limited strains and proteins target coleopteran pests like Anthonomous grandis Boheman, causing substantial economic losses in the cotton industry. This study focuses on characterizing a Bacillus sp. strain, isolated from Oncativo (Argentina), which exhibits ovoid to amorphous parasporal crystals and was designated Bt_UNVM-84. Its genome encodes genes for the production of two pairs of binary Vpb1/Vpa2 proteins and three Cry-like proteins showing similarity with different Cry8 proteins. Interestingly, this gene content was found to be conserved in a previously characterized Argentine isolate of B. thuringiensis designated INTA Fr7-4. SDS-PAGE analysis revealed a major band of 130 kDa that is proteolytically processed to an approximately 66-kDa protein fragment by trypsin. Bioassays performed with spore-crystal mixtures demonstrated an interesting insecticidal activity against the cotton boll weevil A. grandis neonate larvae, resulting in 91% mortality. Strain Bt_UNVM-84 is, therefore, an interesting candidate for the efficient biological control of this species, causing significant economic losses in the cotton industry in the Americas.

Interaction of insecticidal proteins from Pseudomonas spp. and Bacillus thuringiensis for boll weevil management.

Cotton crop yields are largely affected by infestations of Anthonomus grandis, which is its main pest. Although Bacillus thuringiensis (Bt) derived proteins can limit insect pest infestations, the diverse use of control methods becomes a viable alternative in order to prolong the use of technology in the field. One of the alternative methods to Bt technology has been the utilization of certain Pseudomonas species highly efficient in controlling coleopteran insects have been used to produce highly toxic insecticidal proteins. This study aimed to evaluate the toxicity of IPD072Aa and PIP-47Aa proteins, isolated from Pseudomonas spp., in interaction with Cry1Ia10, Cry3Aa, and Cry8B proteins isolated from B. thuringiensis, to control A. grandis in cotton crops. The genes IPD072Aa and PIP-47Aa were synthesized and cloned into a pET-SUMO expression vector. Moreover, Cry1Ia10, Cry3Aa, and Cry8B proteins were obtained by inducing recombinant E. coli clones, which were previously acquired by our research group from the Laboratory of Bacteria Genetics and Applied Biotechnology (LGBBA). These proteins were visualized in SDS-PAGE, quantified, and incorporated into an artificial diet to estimate their lethal concentrations (LC) through individual or combined bioassays. The results of individual toxicity revealed that IPD072Aa, PIP-47Aa, Cry1Ia10, Cry3Aa, and Cry8B were efficient in controlling A. grandis, with the latter being the most toxic. Regarding interaction assays, a high synergistic interaction was observed between Cry1Ia10 and Cry3Aa. All interactions involving Cry3Aa and PIP-47Aa, when combined with other proteins, showed a clear synergistic effect. Our findings highlighted that the tested proteins in combination, for the most part, increase toxicity against A. grandis neonate larvae, suggesting possible constructions for pyramiding cotton plants to the manage and the control boll weevils.

Pest categorisation of Diaprepes abbreviatus.

The EFSA Panel on Plant Health performed a pest categorisation of the citrus root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) for the European Union (EU) following the commodity risk assessment of Ligustrum delavayanum topiary grafted on L. japonicum plants from the UK in which D.abbreviatus was identified as a relevant non-regulated EU pest which could potentially enter the EU. This species is native to the Caribbean and was introduced to the continental USA in 1964, to Gran Canaria (Spain) in 2014 and to Madeira Island (Portugal) in 2018. It is a polyphagous insect, associated with more than 270 species in 60 plant families. Female D. abbreviatus can lay up to 5,000 eggs in clusters within leaves folded and glued together. Neonate larvae drop off the leaves onto the ground and enter the soil, where they feed on roots for several months. The mature larvae pupate in the soil. After emergence, adults usually stay on the first host plant they encounter and can move long distances on nursery stock. D. abbreviatus is not a regulated pest in the EU. It could enter and spread within the EU via the import and movement of host plants for planting, cut flowers and soil. Some host plants for planting (e.g. Vitis spp., Citrus spp.), and soil are prohibited from entering the EU from countries where this weevil is known to occur. The import of other host plants for planting and cut flowers is subject to phytosanitary certificate and that of soil attached to machinery is regulated. Host availability and climate suitability suggest that the southernmost coastal areas of southern EU MSs would be suitable for establishment of D. abbreviatus. Temporary establishment in greenhouses in other EU territories would be possible. The introduction of D. abbreviatus would likely cause impacts. Measures to prevent entry, spread and impact are available. D. abbreviatus satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Efficacy of native Bacillus isolates against different larval instars of fall armyworm, Spodoptera frugiperda alone and in combination

BackgroundFall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) Lepidoptera: Noctuidae is an invasive polyphagous pest that causes severe damage to several agricultural crops. The use of pesticides is limited because of their mode of feeding and resistant development. Hence, the present work aimed to determine the pathogenicity of entomopathogenic bacteria (Bacillus spp.) against FAW in terms of mortality and growth inhibition. In this study, initially 49 native Bacillus isolates, isolated from diverse habitats in India, along with five reference strains, were screened for their efficacy against neonates of S. frugiperda under controlled laboratory conditions, followed by virulence and combinatorial bioassays.ResultsFive native Bacillus isolates (VKK1, VKK5, S16C2, S25C1, and SOIL 20) showed mortality in the range of 35.49–65.52% against neonates of S. frugiperda at single concentration (1000 μg g−1 of diet). These five isolates, along with one reference strain Btk-HD1 (Bacillus thuringiensis serovar kurstaki strain HD1), were further tested to find the median lethal concentration (LC50) for neonates of S. frugiperda. Among these, native Bt strain VKK5 showed the lowest LC50 (718.40 µg/g of diet) and HD1 showed the highest LC50 (3352 µg/g of diet). Combinatorial bioassay against neonate and third instar larvae showed that the combination of VKK5 and VKK1 had an additive effect. Moreover, growth inhibition was also recorded.ConclusionThe combination of Bt strains leads to an enhancement of pathogenicity toward FAW larvae at the initial stage of development, and in later stages, it affects their growth and development. Thus, biocontrol of FAW by entomopathogenic bacteria (Bt) can play a vital role in the effective management of FAW.

Life table study of Sitotroga cerealella on different cereals and its implications on the performance of the egg parasitoid (Trichogramma chilonis) under laboratory conditions

Sitotroga cerealella is one of the major pests of cereals in the field and storage conditions throughout the world. The main objective was to study the life tables of S. cerealella on wheat, maize and barley and its implications on percent parasitism of Trichogramma chilonis. S. cerealella is reared under lab conditions as its eggs are utilized for rearing T. chilonis. Fresh eggs of S. cerealella were collected and after hatching the neonate larvae of S. cerealella were transferred onto each host plant species for obtaining first (F1) generation (G). Seventy eggs were used for each host and each egg was used as a replicate. Daily observations were made for recording the life-table parameters of the S. cerealella. The data showed that the developmental time of S. cerealella eggs and pupae was maximum (5.68 and 7.75 days) when reared on wheat, while the maximum larval duration (19.77 days) of S. cerealella was recorded on barley. The maximum fecundity (290.30 ± 22.47 eggs/female) was recorded on maize, while minimum fecundity per female was recorded on barley (159.30 eggs/ female). The S. cerealella reared on maize had significantly higher values of finite rate of increase (λ), intrinsic rate of increase (r), and net reproductive rate (Ro) (0.14 ± 0.04 day− 1, 1.16 ± 0.05 day− 1, and 136.85 ± 20.25 eggs/ female) respectively. The mean generation time (T) (35.18 ± 0.61 days) was higher on wheat. Likewise, the gross reproductive rate (GRR) and the age-stage specific reproductive values (vxj) of newly oviposited eggs of S. cerealella were recorded higher (136.85 ± 20.25; 1.160 offspring) on maize. The data regarding the efficacy of T. chilonis for different parameters were recorded higher on maize i.e., percent parasitism (89.00 ± 2.30%), percent adult emergence (81.60 ± 1.20%), adult longevity (3.80 ± 0.10 days) and total adult longevity (9.90 ± 0.20 days) as compared to wheat and barley. Our findings revealed that S. cerealella can be best reared on maize under laboratory conditions as it prefers this host as compared to wheat and barley. Therefore, assigning the most susceptible and favorite host (maize) would help us to improve T. chilonis mass production under laboratory conditions.

Buckwheat (Fagopyrum esculentum): its impact on wireworm development and survival

Buckwheat (Fagopyrum esculentum) is a member of the Polygonaceae family, cultivated as a cover crop to suppress or reduce weeds and improve soil health. In our field studies, buckwheat gave significant potato tuber protection from wireworm damage after two consecutive years of cropping. In this study, we identified the mechanism underlying the beneficial effect of buckwheat on wireworm suppression. Results show high wireworm numbers in buckwheat than other host plants in bioassays conducted under greenhouse and field conditions which reject the hypothesis that buckwheat has antifeedant activity. We found that newly hatched neonate wireworms feeding on either barley or buckwheat plants for 120 days, showed reduced body weight and head capsule size. The larvae feeding on buckwheat were 60% and 30% smaller than the ones feeding on barley. Survival was also impacted with 44% of the neonate larvae surviving on barley plants, and only 15% when feeding on buckwheat roots over 120 days. A similar bioassay with small to medium-sized wireworms showed higher mortality, lower weight gain and smaller head capsule size. Wireworms feeding on buckwheat were deformed and demonstrated irregular growth. In conclusion, this study revealed that buckwheat did not repel wireworms and they chose to feed on the roots despite it not being a good host. Long-term feeding on buckwheat roots caused reduced weight gain, abnormal growth, and reduced survival. This study provided a better understanding of how buckwheat functions as a biopesticide for wireworm control and its potential for use in an IPM program.

A review on destructive tomato pest, <i>Phthorimaea absoluta</i> (Lepidoptera: Gelechiidae) and its management

Tomato has extremely important health benefits which make it an important crop all around the world. Among several insect pests of tomato, Tuta absoluta is the most devastating pest. This insect-pest has become one of the leading pests of tomato plants in recent years. The yield losses are often in the range of 80-100%. Larval stages of Tuta absoluta are by far the most destructive stage of the insect because of its feeding habits. The neonate larvae feed on tomato fruits, leaves, flower buds and young shoots. Several chemical insecticides are used against this pest but resistance development to insecticides was reported. There is need of integrated pest management to control the pest population. This review discusses about the harmful effect of chemical pesticides and alternative methods to control Tuta absoluta population. Different methods of pest control include botanical control, biological control and new emerging techniques of green synthesized nanoparticles.

Movement of Striacosta albicosta (Smith) (Lepidoptera: Noctuidae) Larvae on Transgenic Bt and Non-Bt Maize.

Exposure of lepidopteran pests to Bacillus thuringiensis (Bt) proteins has been shown to affect the behavior of larvae, including increased movement and avoidance of Bt-expressing plants or diet. Therefore, we hypothesized that the behavior of western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), an important pest of maize, could be affected when exposed to Bt plants. To test this hypothesis, we conducted a series of artificial arena and on-plant experiments to determine S. albicosta neonate behavior when exposed to Bt and non-Bt plant tissue. Video tracking experiments presented neonate larvae with the choice of Bt or non-Bt pollen in a Petri dish for 15 min while being video recorded for analysis with EthoVision software. This study showed an increase in mean velocity and total time spent moving for larvae in the presence of Cry1F vs. non-Bt when compared with Vip3A vs. non-Bt or Cry1F vs. Vip3A. However, there was no difference in total distance moved or time spent in the food zone for all scenarios. Maize tissue choice experiments allowed neonatal larvae the choice of feeding on Bt or non-Bt tassel or leaves for 9 h in Petri dish arenas. This experiment showed that larvae preferred tassel tissue over leaves but did not indicate that larvae could distinguish between Bt and non-Bt tissue. In contrast, on-plant experiments (including a whole plant neonate dispersal study under controlled conditions and an in-field silking behavior experiment) indicated that the presence of Cry1F and Vip3A Bt toxins increased plant abandonment, suggesting that larvae are able to detect and avoid Bt toxins. The discrepancy of these results is likely due to the on-plant studies providing more field-realistic environmental conditions and a longer duration of exposure to Bt toxins for the behavioral experiments. Our results represent the first steps in understanding the complex behavior of S. albicosta when exposed to Bt plants. A better understanding of the response of larvae when exposed to Bt traits can aid in the management of this pest, particularly for the design of resistance management strategies and refuge design.