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The rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most destructive rice pests in Asian countries. Rice varieties resistant to the rice leaf folder are generally characterized by high silicon content. In this study, silicon amendment, at 0.16 and 0.32 g Si/kg soil, enhanced resistance of a susceptible rice variety to the rice leaf folder. Silicon addition to rice plants at both the low and high rates significantly extended larval development and reduced larval survival rate and pupation rate in the rice leaf folder. When applied at the high rate, silicon amendment reduced third-instars' weight gain and pupal weight. Altogether, intrinsic rate of increase, finite rate of increase and net reproduction rate of the rice leaf folder population were all reduced at both the low and high silicon addition rates. Although the third instars consumed more in silicon-amended treatments, C:N ratio in rice leaves was significantly increased and food conversion efficiencies were reduced due to increased silicon concentration in rice leaves. Our results indicate that reduced food quality and food conversion efficiencies resulted from silicon addition account for the enhanced resistance in the susceptible rice variety to the rice leaf folder.

In South America, especially in Brazil, four members of the Spodoptera complex, Spodoptera albula (Walker, 1857) , S. cosmioides (Walker, 1858) , S. eridania (Stoll, 1782) , and S. frugiperda (J.E. Smith, 1797) are important pests of many crops, in particular corn, soybean and cotton crops. Spodoptera eridania and S. frugiperda have recently invaded Africa and caused serious crop damage, and S. frugiperda has invaded Asia and Oceania. The present study tested the effect of a range of seven temperatures (18–34 °C) on these four Spodoptera species simultaneously, assessing several biological variables. Based on the thermal tolerances obtained experimentally, the ecological zoning of each species in Brazil was mapped and compared spatially, according to the crop calendar of three important crops in different regions (first and second corn harvest, soybean and cotton). Our results showed that S. eridania had the lowest temperature threshold ( T t ) , i.e., it is favored in regions with more moderate temperatures; and did not tolerate the warmest temperature, failing to complete its development at 34 °C. In contrast, S. albula did not complete its development at 18 °C and may be more successful in warmer regions. In general, S. frugiperda and S. cosmioides were able to develop over a wide range of temperatures, and S. frugiperda showed a higher biological potential at all temperatures evaluated. Our biological data and the computational code are available online. The extensive data produced here can help other entomologists to delimit the spatial distribution of the Spodoptera complex and forecast outbreaks of these pests.

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.

Abstract The Spodoptera complex of the family Noctuidae, represented here by S. frugiperda (J.E. Smith), S. eridania (Stoll), S. albula (Walker), and S. cosmioides (Walker), is an important group of crop pests in Brazil. Spodoptera frugiperda and S. eridania are invasive in Africa, and the former also in Asia and Oceania. The egg parasitoids Telenomus remus Nixon (Hymenoptera: Scelionidae) and Trichogramma spp. (Hymenoptera: Trichogrammatidae) are potential control agents for field use against these noctuids. We evaluated the parasitism efficiency, development, and flight capacity of an isofemale line and a regular line of T. remus, and 2 genetically variable populations of Trichogramma pretiosum Riley and Trichogramma atopovirilia Oatman and Platner (Hymenoptera: Trichogrammatidae) in these 4 members of the Spodoptera complex. All parasitoids were able to develop in the 4 hosts. The parasitoids showed good flight capacity, except for the regular line of T. remus. The Trichogramma species, despite having high viability and female:male sex ratios, showed poorer parasitism performances than T. remus. The regular T. remus line also showed good parasitism capacity and high viability but had a predominance of males. In general, the isofemale line of T. remus showed good rates of parasitism and flight capacity as well as a high viability and sex ratio, proving to be a potential candidate for an augmentative biological-control program for Spodoptera spp Guenée (Lepidoptera: Noctuidae).

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.

In Africa, the current harmful maize pest is Spodoptera frugiperda. Its attack can be severe and cause total economic losses. Spodoptera eridania is another species of the same genus, detected a few months after S. frugiperda’s outbreaks in West and Central Africa. Though both species share a range of host plants, socioeconomic studies are yet to provide specific figures on the potential impacts of S. eridania. The high and inappropriate application of insecticides to control Spodoptera species has negative effects on the environmental elements’ health. Semiochemical tools are increasingly exploited to design alternative pest management strategies. We hypothesize that host plants release components used by the pests and a shared parasitoid to locate the host. To verify that hypothesis, we conducted behavioral assays and GC-MS analyses to identify the potential chemical signals involved in the communications of the moths and their shared parasitoid C. icipe. The results showed that healthy and herbivory-induced maize and amaranth produced some chemical compounds including α-pinene, limonene, isopentyl acetate, (Z)-beta-farnesene, and methyl dodecanoate, which prospects their potential use in alternative pest management strategies for recruiting C. icipe to control these pests. Further work will focus on field validation to develop an alternative control strategy for the moths.

Abstract Spodoptera eridania (Stoll) is a key pest of soybean crops in Brazil. However, information about the physiology, behavior, and ecology of S. eridania, including its genetic variability within the agricultural landscape, remains scarce. In this study, we conducted an exploratory analysis of the genetic diversity, population structure, and demographic patterns of S. eridania in Brazil. A cytochrome c oxidase I (COI) gene fragment of 866 bp was sequenced from 89 S. eridania individuals collected in Brazilian soybean macroregions. We identified 33 COI haplotypes with high haplotype diversity and moderate nucleotide diversity distributed throughout the country. The genetic relationships among COI haplotypes show a recent divergence with no evidence of distinct haplogroups. Spodoptera eridania collected on soybean crops showed a lack of population genetic structure associated with soybean macroregions or Brazilian states. Overall, our data suggest that S. eridania populations are undergoing demographic and spatial expansion in Brazil, with an increasing effective population size in the last 200 years. This study provides the first insights into the population diversity and demography of S. eridania in the Americas, shedding light on the dynamics and evolution of this species and further supporting integrated pest management strategies in Brazilian soybean crops.

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) and southern armyworm (SAW) Spodoptera eridania (Stoll) have become major threats to crops in Africa since 2016. African governments adopted emergency actions around chemical insecticides, with limited efforts to assess the richness or roles of indigenous natural enemies. Field surveys and laboratory studies were conducted to identify and assess the performance of parasitoids associated with spodopterans in Cameroon. FAW was the most abundant spodopteran pest. Telenomus remus (Nixon), Trichogramma chilonis (Ishi), Charops sp. (Szépligeti), Coccygidium luteum (Cameron), Cotesia icipe (Fernandez & Fiaboe), and Cotesia sesamiae (Cameron) are the first records in the country on spodopterans. Telenomus remus, T. chilonis, C. icipe, and Charops sp. were obtained from both FAW and SAW; C. luteum and C. sesamiae from FAW. The distribution of spodopterans, their endoparasitoids, and parasitism rates varied with host, season and location. In the laboratory, T. remus showed significantly higher parasitism on FAW than SAW, and significant differences in the development parameters between the two host eggs, with shorter development time on FAW. It induced significant non-reproductive mortality on FAW but not on SAW. Developmental parameters showed that C. icipe has a shorter development time compared to other larval parasitoids. Implications for conservative and augmentative biocontrol are discussed.

Non-target organisms are not well studied. The objective of this work was to evaluate the effect of seven essential oils, two fixed oils, d-limonene and eugenol on the mortality, behavior and infectivity of entomopathogenic nematodes (ENPs). The oils were diluted at 1% (v/v) in water with Tween® 80 PS at 0.05% (v/v), and water with Tween® alone was used as the control treatment. In the mortality test, 2 mL of solution containing 50 µL of the nematode suspension, 20 µL of oil/compounds solution isolated with Tween 80, and 1930 µL of water were placed in plastic containers. After four days, the number of dead juveniles was counted. In the bioassay of the behavior of the EPNs, the frequency of lateral body beats of the infective juveniles in liquid medium was analyzed after exposure to the solutions. In the infectivity test, after contact of the EPNs with oils and essential oil chemical compounds, the juveniles were washed and applied to second-instar Spodoptera eridania larvae. All oils and isolated compounds caused mortality in H. amazonensis and S. rarum, with Ocimum canum and the isolated compound eugenol showing the highest efficacy against H. amazonensis and O. canum, Eucalyptus citriodora, Zingiber officinale, Salvia sclarea and the isolated compound eugenol being the most effective against S. rarum. There was a reduction in the number of lateral beats of H. amazonensis and S. rarum for all treatments, with the exception of Cymbopogon winterianus in H. amazonensis and Annona muricata in S. rarum. The infectivity of H. amazonenis and S. rarum on S. eridania was reduced when exposed to the solutions, with the exception of the isolated compound d-limonene in both species, soursop for H. amazonenis and rosemary for S. rarum, which were classified as non-toxic to the species tested. The results obtained in this study may be useful for the choice of oils and essential oil chemical compounds with potential use in integrated pest management programs.

Lima bean plants (Phaseolus lunatus) exhibit compensatory growth responses to herbivory. Among the various factors that have been identified to affect plant compensatory growth are the extent and type of tissue damage, the herbivore’s feeding mode and the time of damage. Another factor that can greatly impact plant responses to herbivory, but has been largely ignored in previous studies, is the action of parasitoids. In most cases, parasitoids halt or slow down the development of herbivorous hosts, which, can result in decreased leaf damage, thereby affecting plant responses and ultimately plant fitness. Here, we investigated the effects of two koinobiont parasitoids on the amount of leaf damage inflicted by the Southern armyworm Spodoptera latifascia to wild lima bean, and the consequences of this for plant growth and seed production in the field. We specifically tested the hypothesis that the action of parasitoids will reduce plant damage and that this reduction will alter plant growth responses and seed production. Indeed, we found that in the presence of parasitoids plants suffered less damage than plants with only herbivores. As a consequence, compensatory growth was reduced and more and heavier seeds were produced earlier in the season, compared to plants exposed to only herbivores.