Spodoptera Eridania Research Articles

Biology of Spodoptera Eridania (Cramer, 1792) (Lepidoptera: Noctuidae) at Different Temperatures and Diet Sources

Objective: This work aimed to study the biological aspects of Spodoptera eridania, reared at different temperatures; and fed artificial and natural diets. Methods: In climatic chambers, the insects were subjected to six constant temperatures (15, 19, 23, 27, 31, and 35 °C). At all temperatures, both types of diet were offered to obtain data on cycle duration, viability, and total oviposition. Results and Conclusion: The different temperatures and diets influenced the insect development stages and the egg-adult cycle. The development of S. eridania is inversely proportional to the increase in temperature. Research Implications: The study confirmed differences in insect development in different diet sources and at different temperatures, and can be applied to S. eridania breeding techniques in research laboratories. Originality/Value: This research contributes by exploring the developmental biology of the pest organism, and can be used in research laboratory methodologies for pest breeding and commercialization for studies of more sustainable agricultural practices.

Curcumin and carvacrol co-loaded zein nanoparticles: Comprehensive preparation and assessment of biological activities in pest control

To address the escalating global demand for food production, it is imperative to minimize agricultural losses caused by pests, accounting for up to 40 % of the substantial worldwide losses of 70 billion USD. While conventional pesticides raise environmental concerns, environmentally friendly alternatives like curcumin and carvacrol face low biological activity due to their low solubility and premature degradation in environmental conditions, that is, degradation can occur due to solar radiation, high temperature, etc., before the active ingredients can exert its full potential. This study introduces zein-based nanocarriers encapsulating curcumin and carvacrol, exhibiting favorable characteristics. Cytotoxicity tests indicate approximately 60% viability for fibroblast cell lines compared to 20% for keratinocyte cell lines. The nanoencapsulated compounds exhibit promising biological activity against soybean pests, mites, and caterpillars, without causing phytotoxicity. Tetranychus urticae mortality rates reach 77.1 ± 11.5 %, and nanoencapsulated ingredients demonstrate higher repellency (61.1 ± 8.8%) than emulsified ones (51.1 ± 5.4 %). Nanoencapsulated ingredients exhibit significantly higher mortality rates for Spodoptera cosmioides and Spodoptera eridania, underscoring the potential of nanoencapsulation in bolstering bioactivity against specific pests and promoting sustainable agricultural practices.

A new biocontrol agent against old enemies: The potential of Trichogramma foersteri for the control of Spodoptera frugiperda and Spodoptera eridania

Species of the genus Trichogramma Westwood (Hymenoptera: Trichogrammatidae) are widely used for pest control, highlighting the importance of exploring new species for the advancement of biological control programs. The study aimed to evaluate the efficacy of Trichogramma foersteri Takahashi, a recently discovered species, in controlling Spodoptera frugiperda (JE Smith) and S. eridania (Stoll), two significant pests of numerous cash crops. Over three days, the research examined parasitism, non-reproductive mortality, and emergence rates for both pest species. Trichogramma foersteri demonstrated effective parasitism, reducing 144.1 ± 6.0 eggs (one layer) and 55.4 ± 4.0 eggs (two layers) of S. frugiperda, as well as controlling 150.7 ± 5.6 eggs of S. eridania. Non-reproductive effects contributed significantly to mortality, causing the demise of 192.6 ± 4.7 and 118.6 ± 3.8 eggs in one and two layers of S. frugiperda, and 294.7 ± 7.0 eggs in S. eridania. Within three days, T. foersteri controlled approximately 334.2 ± 7.6 and 174.0 ± 4.0 eggs of S. frugiperda in one and two layers, respectively, and 445.4 ± 7.2 eggs of S. eridania. The highest emergence of T. foersteri occurred on the first day of evaluation, with 80.4 % for S. frugiperda and 23.0 % for S. eridania. These findings underscore the potential of T. foersteri as an effective control agent for both pests and provide valuable insights for the development of sustainable pest control strategies.

Use of plant extracts (Ricinus communis) to control undesirable insects in the cultivation of caupi beans

The objetive was to evaluate the action of the extracts from the castor bean plant, the shells of the seeds, the seeds and the leaves of the castor bean plant on the insects that are likely to cause damage in the caupi-bean plant. The experiment was carried out at the Federal Institute of Education, Science and Technology of Pará (IFPA- Campus Bragança) located in the municipality of Bragança, located in the northeast region of the state of Pará. The trials were conducted in the first half of 2023, namely: 1-Screening of castor bean by-products, seed hulls, seeds and castor bean leaves using ethanol as solvent; 2- Dose response curve extracting bioactive substances from seed, seed and leaf hulls with ethanol. Casualized blocks (CBD) with three repetitions and four treatments, divided into four blocks, each block had 50 plants with plant spacing of 20cm and 50 cm between rows with local breaded bean cultivar. Treatments were applied once/week after the infestation appeared, after filtering dilution was done for each case in a single spray. Testing of formulates with an interval of one week in each treatment were applied: witness, MSM, SM and FoM, all using ethanol at 92.8° INPM in the preparation of SE and applied in the dosage of 10%(m/v). Evaluation of treatments was performed 48 hours after spraying by counting live and dead insects. The effects of oil and leaf and shell extracts from the castor bean plant on mortality of aphids, caterpillars, bedbugs and cowpeas in beans were investigated using second order regression analyzes. The analyzes were carried out in the Past 4.14 program. As the concentration of oil extracted from castor bean seeds is increased, there is an increase in the mortality rate. The concentrations of aqueous extracts from the castor bean leaves, more efficiency in the results. Thus, the plant extracts tested are a viable alternative for the control of Aphis craccivora, Bemisia tabaci, Diabrotica speciosa, Spodoptera eridania and Nezara viridula, being affordable products for easy preparation and application.

Bacillus thuringiensis strains to control Noctuidae pests

AbstractThis study aimed to select and characterize Bacillus thuringiensis strains with toxic activity on Helicoverpa armigera, Spodoptera cosmioides and Spodoptera eridania. Fifty B. thuringiensis (Bt) strains were used in selective bioassays for high mortality on H. armigera, and the four most efficient strains were tested on S. cosmioides and S. eridania. Twelve Bt strains were characterized by PCR to detect some cry, cyt and vip genes. Bioassays were also performed to detect the production of β‐exotoxins. Strain 237 caused a mortality rate of 95.6% due to β‐exotoxins. Strains 1368, 1521, 1814 and 3299 showed toxic activity on S. eridania. However, no strain was effective on S. cosmioides. The presence of β‐exotoxin was detected only in strain 237. The molecular characterization of the strains using specific cry, cyt and vip primers showed a great genetic diversity among the 12 strains that showed some mortality on H. armigera and S. eridania. Our results showed that detecting β‐exotoxin in Bt strains is important as it is toxic to insects and vertebrates and persistent in the environment. Strains 1368, 1521, 1814 and 3299 did not show toxicity to H. armigera, while they were toxic to S. eridania and did not produce β‐exotoxin. These strains may be useful for new formulations of biopesticides as well as for cloning and expression of plants' genes.

Biology of Spodoptera eridania (Stoll) in the cultivation of grape (Vitis vinifera L.) under laboratory conditions

The grape crop (Vitis vinifera L.) in the Piura region is infested by pests such as Spodoptera eridania Stoll, a polyphagous species native to the South American tropics. The objective of carrying out the research work was to know basic aspects about its morphology and biology, because there were no records of them in this crop, nor in others in the region. Daily observations were made to determine the duration of the egg incubation period, larval development, and the pupal stage and adult longevity. Once the adults emerged, they mated to establish the oviposition rhythm and reproductive capacity; all these parameters were evaluated for three generations. It was determined that, under laboratory conditions, the development cycle of S. eridania was 34.90 days for the first generation, 31.16 and 28.60 days for the second and third, with an average temperature record of 27.97 °C and relative humidity of 71.86%. The results show that it can be developed in vine plantations and will be useful in planning the work of the crop and in establishing integrated pest management strategies to reduce infestations when they occur.

Temperature-dependent reproduction of Spodoptera eridania: developing an oviposition model for a novel invasive species.

Temperature plays a critical role in the development and reproductive process of insects, therefore understanding how insects respond to temperature is vital for comprehending and predicting their population dynamics, particularly when it comes to agricultural pests. Spodoptera eridania Stoll is a polyphagous pest that has recently expanded its distribution beyond its native range. In this study, we assessed the impact of temperature on the reproduction of S. eridania and used the obtained data to develop an oviposition model that could be used to predict egg-laying behavior under field conditions. The reproductive parameters were evaluated at temperatures of 15, 20, 25, 28, and 32 °C. Temperature had a significant impact on the reproductive parameters examined. Overall, as temperature increased, the pre-oviposition period, oviposition period, and longevity decreased. Total fecundity exhibited a bell-shaped response to temperature, with peak egg-laying observed at 20 and 25 °C. In line with the experimental data, our model predicted higher rates of oviposition between 20 and 26 °C, thus reinforcing that this temperature range may represent the optimal conditions for the reproduction of S. eridania. The findings from our study provide a significant contribution to the understanding of the ecology of an important agricultural pest. The information generated can have practical applications in developing control strategies by enabling the aligning of the timing of control measures with peaks of reproductive activity. © 2023 Society of Chemical Industry.

Dose Effects of Flubendiamide and Thiodicarb against Spodoptera Species Developing on Bt and Non-Bt Soybean.

An increase in Spodoptera species was reported in Bt soybean fields expressing Cry1Ac insecticidal proteins in Brazil, requiring additional management with chemical insecticides. Here, we evaluated the dose effects of flubendiamide and thiodicarb on Spodoptera cosmioides (Walker, 1858), Spodoptera eridania (Stoll, 1782), Spodoptera albula (Walker, 1857) and Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) that survived on MON 87751 × MON 87708 × MON 87701 × MON 89788, expressing Cry1A.105, Cry2Ab2 and Cry1Ac; MON 87701 × MON 89788 soybean, expressing Cry1Ac; and non-Bt soybean. On unsprayed Cry1A.105/Cry2Ab2/Cry1Ac soybean, only S. frugiperda showed ~60% mortality after 10 d, whereas S. cosmioides, S. eridania and S. albula showed >81% mortality. The surviving larvae of all species on this Bt soybean showed >80% mortality when exposed to the field label dose of flubendiamide (70 mL/ha) or thiodicarb (400 g/ha) or at 50% of these doses. In contrast, all four species had <25% and <19% mortality on Cry1Ac and non-Bt soybean, respectively. The surviving S. cosmioides, S. eridania and S. albula on these soybean types presented >83% mortality after exposure to both dose levels of flubendiamide and thiodicarb. Some S. frugiperda larvae surviving on Cry1Ac and non-Bt soybean sprayed with a 50% dose of either insecticide developed into adults. However, the L1 larvae developing on Cry1Ac soybean leaves sprayed with flubendiamide and the L2 larvae on this soybean sprayed with thiodicarb had a prolonged immature stage, and the females displayed lower fecundity, which are likely to impact S. frugiperda population growth on soybean.

Global Potential Geographical Distribution of the Southern Armyworm (Spodoptera eridania) under Climate Change.

The southern armyworm (Spodoptera eridania), a polyphagous crop pest native to tropical America, has been found in Africa (2016) and India (2019), causing defoliation and damage to the reproductive structures of cassava, soybean, and tomato. The damage caused by this pest to crop systems has raised concerns regarding its potential risks. Therefore, we predicted the potential geographical distribution of S. eridania under climate change conditions using 19 bioclimatic variables based on an optimized MaxEnt model. The results showed that annual precipitation (bio12), mean temperature of the warmest quarter (bio10), and precipitation of the driest month (bio14) were important bioclimatic variables influencing the potential distribution. The prediction showed that the suitable habitat area was approximately 3426.43 × 104 km2, mainly concentrated in southern North America, South America, western Europe, central Africa, southern Asia, and eastern Oceania. In response to global climate change, suitable habitats for S. eridania will expand and shift to higher latitudes in the future, especially under the SSP5-8.5 scenario. Because of the current devastating effects on crop production, countries without S. eridania invasion, such as the European Union, Southeast Asian countries, and Australia, need to strengthen phytosanitary measures at border ports to prevent the introduction of this pest.

Toxicity of the Hexane Fraction of Fruits and Seeds of Ricinus communis to Caterpillars of the Spodoptera Complex

The objective of this work was to evaluate the effect of the hexane fraction of the crude extract of the fruits and seeds of Ricinus communis (HFFSRC) on eggs of Spodoptera cosmioides and Spodoptera frugiperda and on caterpillars of Spodoptera eridania, S. frugiperda, and S. cosmioides, under laboratory conditions through topical application and ingestion, as well as to identify the compounds in the hexane fraction through high-performance chromatography (HPLC-ESI-Q-TOF-MS/MS). To do so, three bioassays were conducted: (1) the effect of HFFSRC at 2% (20,000 mg·mL−1) on eggs of S. cosmioides and S. frugiperda, (2) the lethal effect of HFFSRC at 2% applied topically, and (3) the lethal effect of HFFSRC at 2% applied to soybean-leaf discs on first-, second-, third-, and fourth-instar caterpillars of the three insect species. It was found that 2% HFFSRC had an ovicidal effect on S. frugiperda and S. cosmioides, completely reducing larvae hatching and the insecticidal effect for the four instars of the three insect species when applied topically and on food. Five compounds were identified in the HFFSRC: three flavonoids, one ricinoleic acid, and one cinnamic acid. HFFSRC at 2% had an acute ovicidal and insecticidal effect on caterpillars of the studied species, configuring itself as a potential insecticide.

D-limonene-based formulations for the management of Diaphania hyalinata, Plutella xylostella and Spodoptera eridania in a greenhouse

Diaphania hyalinata, Plutella xylostella and Spodoptera eridania are considered important pests in vegetable crops, causing significant production losses. The most common method for managing these pests is the use of synthetic insecticides that cause chain damage, from human health to the environment. A less aggressive alternative is the use of botanical insecticides, such as essential oils, which present themselves as potential for the composition of bioinsecticides. In the present study, the efficiency of formulations based on d-limonene (major compound of the orange peel oil - Citrus sinensis) on the mortality of D. hyalinata, P. xylostella and S. eridania was evaluated. For this purpose, formulations containing d-limonene (2.0%), Tween 80 (0.05%) and water were prepared, combined with different encapsulating agents (xanthan gum, guar gum and maltodextrin) diluted to 2% (v /v). The formulations were sprayed on plants using a sprayer and five second-instar caterpillars were distributed on each plant. The mortality of caterpillars was evaluated 72 h after the application of the formulas. Formulation based on the compound d-limonene with the encapsulating agent guar gum had an effect on the mortality of P. xylostella and S. eridania and formulation with the encapsulating agent maltodextrin had an effect on the mortality of S. eridania.

Azadirachtin-based insecticide impairs testis morphology and spermatogenesis of the southern armyworm Spodoptera eridania (Lepidoptera: Noctuidae).

In the search for alternative tools for integrated pest management, azadirachtin, a botanical insecticide, has been used with the most promising activity against Spodoptera spp., but the mechanism of cytotoxicity on reproductive organs remains unclear. Spodoptera eridania (Stoll, 1782) is a polyphagous pest with great economic importance that has become an important target to elucidate the action of azadirachtin on the reproductive organs of insect pests, helping to understand the deleterious effects caused by its exposure. This study evaluated the effects of chronic exposure to azadirachtin on the morphology and ultrastructure of S. eridania larval testes as well as larval development. Azadirachtin exposure (6 or 18 mg a.i.L-1 ) caused a progressive increase in cumulative mortality and reduced gain in body mass after 5 days. Testicular structure indicated a reduction in their size with internal morphological changes such as spermatogonia, spermatogonial, spermatocytes and spermatid cysts in degeneration. The occurrence of cell death in germ and somatic cells was evidenced by the TUNEL technique. Electron microscopy revealed changes in cystic cells, such as cytoplasmic membrane rupture and cytoplasmic vacuolization. Chromatin compaction, changes in the rough endoplasmic reticulum and Golgi complex cisternae were observed in germ cells. Apoptotic bodies occurred between germ cell cysts. Azadirachtin damaged the testes of S. eridania larvae, and these changes compromised spermatogenesis and consequently the development of the reproductive potential of this specimen, making azadirachtin a promising botanical insecticide for application in integrated pest management programs. © 2022 Society of Chemical Industry.

Feeding injury of major lepidopteran soybean pests in South America.

Lepidopteran pests are major factors limiting soybean productivity in South America. In some cases, effective management of these species requires the use of foliar insecticides. For sustainable use of these insecticides, they should only be applied when insect population size exceeds an economic threshold. Since this estimation requires to determine the consumption of different species, this work aimed to integrate all these factors, studying the consumption of small (less than 1 cm long) and medium (1 to 1.5 cm long) size larvae of major lepidopteran pests to vegetative and reproductive tissues on Bt (M7739IPRO variety, containing the event MON87701 which expresses the Cry1Ac protein from Bacillus thuringiensis) and non-Bt (BMX Desafio RR variety) soybeans. The feeding injury to vegetative tissues was tested in detached-leaf assays in grow chambers, and for reproductive structures the study was conducted in greenhouse with infestations at early (flowering) and mid reproductive (mid grain filling) stages. Based on the feeding behavior of the species tested, they were cast in four groups: a) Anticarsia gemmatalis and Chrysodeixis includens, defoliating only the RR variety with the lowest consumption of foliar area; b) Spodoptera eridania, defoliating both RR and IPRO varieties, consuming twice than the species mentioned above; c) Helicoverpa armigera, defoliating and being the most damaging species to pods in the RR variety; and d) S. cosmioides and S. frugiperda, defoliating and damaging pods in both varieties. The species differed in their ability to feed on IPRO varieties, so a different economic threshold should be considered. Consequently, in cases where more than one species are found simultaneously, the species composition should be considered in estimating the economic threshold. Additionally, our findings may contribute to a better decision-making to control insect feeding injury in IPRO varieties, because a slower larval growth provides more time to ensure the need of control with insecticides. In summary, this clasification contributes to an improved recommendation of sustainable insecticide use, taking into account the behavior of each species that are major soybeans pests in South America.

Efficiency of essential oils and pure compounds in the management of Plutella xylostella, Spodoptera eridania and Diaphania hyalinata

The use of essential oils and pure compounds are promising in the management of vegetable pests. This study aimed to evaluate the efficiency of commercial essential oils of eucalyptus (Eucalyptus citriodora), rosemary (Rosmarinus officinalis), salvia (Salvia sclarea), basil (Ocimum canum), citronella (Cymbopogon winterianus) and pure compounds eugenol and d-limonene and the oil extracted from ginger (Zingiber officinale Roscoe) in the management of Diaphania hyalinata, Spodoptera eridania and Plutella xylostella. The isolated oils and compounds were applied to 2nd and 4th instar caterpillars of the pests, in the action modes contact and ingestion. Each treatment consisted of six replicates and mortality was assessed after 72 h. The experiments were performed twice for greater data reliability. The design used was a completely randomized double factorial design (products × exposure routes). The results revealed that the pure compound eugenol stood out, presenting an effect in the direct exposure on caterpillars; in the exposure via food, in turn, the pure compound d-limonene stood out, presenting mortality for all instars and pests tested, except for the 4th instar of S. eridania. Thus, the essential oils and pure compounds tested represent valuable tools with potential for integration in the management of vegetable pests.

Spodoptera eridania: Current and emerging crop threats from another invasive, pesticide-resistant moth

Spodoptera eridania: Current and emerging crop threats from another invasive, pesticide-resistant moth

Characterizing the lethal and sub-lethal effects of genetically modified soybean expressing Cry1A.105, Cry2Ab2, and Cry1Ac insecticidal proteins against Spodoptera species (Lepidoptera: Noctuidae) in Brazil.

MON 87701 × MON 89788 × MON 87751 × MON 87708 soybean, that expresses Cry1A.105, Cry2Ab2, and Cry1Ac insecticidal proteins and confers tolerance to glyphosate and dicamba, is a potential tool for managing Spodoptera species in soybean fields in Brazil. In this study, we characterized the lethal and sub-lethal effects of Cry1A.105/Cry2Ab2/Cry1Ac soybean against Spodoptera species and genotypes of Spodoptera frugiperda resistant and susceptible to Cry1 and Cry2 proteins. These evaluations were also conducted with MON 87701 × MON 89788 soybean, which expresses Cry1Ac protein. Cry1A.105/Cry2Ab2/Cry1Ac soybean caused high lethality in neonates of Spodoptera cosmioides and Spodoptera albula. However, it showed low lethality in S. frugiperda genotypes homozygous for resistance to Cry1 and Cry2 proteins but reduced their population growth potential. No relevant lethal effects of Cry1Ac soybean were detected in the Spodoptera species and genotypes evaluated. Spodoptera frugiperda genotypes heterozygous for Cry1 and Cry2 resistance were controlled by Cry1A.105/Cry2Ab2/Cry1Ac soybean, with no insects developing into adults. This Bt soybean also caused intermediate mortality of neonates of Spodoptera eridania (60%-83%) but no surviving larvae developed to adulthood, resulting in population suppression. Cry1A.105/Cry2Ab2/Cry1Ac soybean caused high mortality of S. cosmioides, S. albula, and S. frugiperda genotypes susceptible to Cry1 and Cry2 and heterozygous for Cry1 and Cry2 resistance. This Bt soybean also suppressed population growth of S. eridania but had minimal impact on S. frugiperda homozygous for resistance to Cry1 and Cry2 proteins. Cry1Ac soybean had minimal impact on all Spodoptera species and genotypes evaluated. © 2022 Society of Chemical Industry.

Assessment of Injury by Four Major Pests in Soybean Plants Using Hyperspectral Proximal Imaging

Arthropod pests are among the major problems in soybean production and regular field sampling is required as a basis for decision-making for control. However, traditional sampling methods are laborious and time-consuming. Therefore, our goal is to evaluate hyperspectral remote sensing as a tool to establish reflectance patterns from soybean plants infested by various densities of two species of stinkbugs (Euschistus heros and Diceraeus melacanthus (Hemiptera: Pentatomidae)) and two species of caterpillars (Spodoptera eridania and Chrysodeixis includens (Lepidoptera: Noctuidae)). Bioassays were carried out in greenhouses with potted plants placed in cages with 5 plants infested with 0, 2, 5, and 10 insects. Plants were classified according to their reflectance, based on the acquisition of spectral data before and after infestation, using a hyperspectral push-broom spectral camera. Infestation by stinkbugs did not cause significative differences in the reflectance patterns of infested or non-infested plants. In contrast, caterpillars caused changes in the reflectance patterns, which were classified using a deep-learning approach based on a multilayer perceptron artificial neural network. High accuracies were achieved when the models classified low (0 + 2) or high (5 + 10) infestation and presence or absence of insects. This study provides an initial assessment to apply a non-invasive detection method to monitor caterpillars in soybean before causing economic damage.

Characterization and genomic analyses of a novel alphabaculovirus isolated from the black armyworm, Spodoptera cosmioides (Lepidoptera: Noctuidae)

The black armyworm Spodoptera cosmioides is a pest of increasing importance in Cry1Ac-Bt toxin crops and non-Bt crops of soybean and cotton in Brazil. Here we characterized a baculovirus isolated from extracts of S. cosmioides that died with symptoms of nuclear polyhedrosis. The putative novel virus exhibited polyhedral occlusion bodies (OBs) with virions containing multiple rod-shaped nucleocapsids, characteristic of alphabaculoviruses. The virus isolate was named Spodoptera cosmioides nucleopolyhedrovirus isolate CNPSo-72 (SpcoNPV-CNPSo-72). SpcoNPV-CNPSo-72 was lethal to third-instar S. cosmioides caterpillars but not to S. frugiperda under the tested viral concentrations. Moreover, SpcoNPV-CNPSo-72 contained a circular 147,763 bp long genome and a G + C content of 44.8% with 151 annotated ORFs (10 unique for baculovirus) and five homologous regions (hrs). The 38 currently defined baculovirus core genes were found in the SpcoNPV-CNPSo-72 genome. After phylogenetic analysis, the novel virus was found to be closely related to other members of Alphabaculovirus, especially to the Spodoptera-infecting viruses, which included Spodoptera eridania nucleopolyhedrovirus isolate 251, Spodoptera litura nucleopolyhedrovirus isolate II, Spodoptera exigua multiple nucleopolyhedrovirus isolate US-1, Spodoptera eridania nucleopolyhedrovirus isolate CNPSo-165, and Spodoptera frugiperda multiple nucleopolyhedrovirus isolate 19. Surprisingly, the new baculoviral genome was found to code for a putative arginine-associated tRNA gene with a predicted intronic sequence of 105 nt. The gene was found inside the bjdp CDS. Overall, baculoviruses are pathogens that lethally infect insect larvae and their study allows a better understanding of large DNA virus evolution, which provides important insights for the development and improvement of biological control agents.

Simulated soybean pod and flower injuries and economic thresholds for Spodoptera eridania (Lepidoptera: Noctuidae) management decisions

Although defoliation economic thresholds (ETs) in soybean are well-established, there are concerns about Spodoptera spp. and Helicoverpa spp. damaging soybean pods and flowers. Moreover, S. eridania is the most common species of its genus feeding on soybean in Brazil. On this account, we quantified the feeding of S. eridania larvae on leaves, pods and flowers of BRS388RR and BRS1001IPRO cultivars in the laboratory. In the field, trials were conducted testing artificial injuries for 3 consecutive crop seasons. Results indicated that third-instar S. eridania can grow when feeding on pods (from plants at R3 stage). However, the larval stage is lengthened (27.4 days) compared with larvae feeding on leaves (19.9 days). Tests with older pods (stages R5.1 and R5.5) resulted in 100% mortality. For neonates, 100% mortality was observed for both pod and pod + flower feeding. Also, soybean tolerated all tested injuries in the field, including 25% perforated pods with 16.7% defoliation or 100% flower removal, without yield reduction. Overall, S. eridania is a leaf feeder. Older larvae (from 3rd instar) can feed on pods at an early plant reproductive stage (R3 stage). However, soybean tolerance to pod and flower injuries is high, even when occurring in combination with defoliation. Therefore, an ET of 25% of injured pods or a general defoliation ET of 15% at the reproductive stage is safe. Flower removal at R2 reproductive stage by S. eridania should not trigger management because no reduction in yield was observed even when 100% of flowers were removed.

Interspecific Variation in Susceptibility to Insecticides by Lepidopteran Pests of Soybean, Cotton, and Maize Crops From Brazil

The interspecific variation in susceptibility to insecticides by lepidopteran species of soybean [Glycine max L. (Merr.)], cotton (Gossypium hirsutum L.), and maize (Zea mays L.) crops from Brazil were evaluated. Populations of Anticarsia gemmatalis (Hübner) (Lepidoptera: Erebidae), Chrysodeixis includens (Walker), Helicoverpa armigera (Hübner), Spodoptera frugiperda (Smith), Spodoptera eridania (Stoll), Spodoptera cosmioides (Walker), and Spodoptera albula (Walker) (Lepidoptera: Noctuidae) were collected from 2019 to 2021. Early L3 larvae (F2 generation) were exposed to the formulated insecticides methoxyfenozide, indoxacarb, spinetoram, flubendiamide, and chlorfenapyr in diet-overlay bioassays. The median lethal concentrations (LC50) were used to calculate tolerance ratios (TR) of each species in relation to the most susceptible species to each insecticide. The lowest LC50 values were verified for A. gemmatalis to all insecticides tested. Chrysodeixis includens and most of the Spodoptera species were moderately tolerant to methoxyfenozide (TR < 8.0-fold) and indoxacarb (TR < 39.4-fold), whereas H. armigera was the most tolerant species to methoxyfenozide (TR = 21.5-fold), and indoxacarb (TR = 106.4-fold). Spodoptera cosmioides, S. eridania, and S. albula showed highest tolerance to spinetoram (TR > 1270-fold), S. eridania, S. frugiperda, and S. albula to flubendiamide (TR from 38- to 547-fold), and S. albula to indoxacarb (TR = 138.6-fold). A small variation in susceptibility to chlorfenapyr (TR < 4.4-fold) was found among the lepidopteran evaluated. Our findings indicate a large variation in susceptibility to indoxacarb, spinetoram, and flubendiamide and a relatively low variation in susceptibility to methoxyfenozide and chlorfenapyr by lepidopteran species of soybean, cotton, and maize from Brazil.