RESUMO
Entomopathogenic fungi have been considered potential biological control agents against the fall armyworm Spodoptera frugiperda (J. E. Smith), the world's most important pest of maize. In this study, we evaluated the natural infection, molecular characteristics, and biological activity of Metarhizium rileyi (Farlow) isolated from S. frugiperda larvae of this insect, collected from maize crops in five Mexican locations. Natural infection ranged from 23% to 90% across all locations analyzed. Twenty-four isolates were evaluated on S. frugiperda second instars at a concentration of 1.0 × 108 conidia/mL, causing 70% to 98.7% mortality and 60.5% to 98.7% sporulation. Isolates T9-21, Z30-21, PP48-21, and L8-22 were selected to determine their phylogenetic relationships by ß-tubulin gene analysis and to compare median lethal concentration (CL50), median lethal time (LT50), and larval survival. These isolates were grouped into three clades. The T9-21, PP48-21, and J10-22 isolates were closely related (clade A), but phylogenetically distant from Z30-21 (clade B) and L8-22 (clade C) isolates. These genetic differences were not always reflected in their pathogenicity characteristics since no differences were observed among the LC50 values. Furthermore, isolates T9-21, J10-22, and L8-22 were the fastest to kill S. frugiperda larvae, causing lower survival rates. We conclude that native M. rileyi isolates represent an important alternative for the biocontrol of S. frugiperda.
RESUMO
Over the last decade, essential oils (EOs) have become potential ingredients for insecticide formulations due to their widespread availability and perceived safety. Therefore, this study aimed to evaluate the toxicity and biochemical efficacy of basil (Ocimum basilicum) (Lamiaceae) against two destructive pests Noctuidae, Agrotis ipsilon (Hufnagel) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, a molecular docking study was performed to gain insight into the binding pattern between glutathione S-transferase (GST) and linalool, the main component of EO. GC-MS analysis of O. basilicum EO revealed that linalool is the most abundant compound (29.34%). However, the toxicity tests showed no significant difference between the values of LC50 of O. basilicum EO to A. ipsilon and S. littoralis. On the other hand, the sublethal experiments indicated that treating the second instar larvae with LC15 or LC50 values of O. basilicum EO significantly prolonged the larval duration in both insects, compared to the control. Regarding the biochemical effect of O. basilicum EO, the treatments significantly impacted the activity of detoxification enzymes. A notable elevation in glutathione S-transferase (GST) activity was recorded in A. ipsilon larvae compared with a reduction in S. littoralis larvae. The molecular docking analysis revealed that linalool bonded with the amino acid serine (SER 9) of GST, indicating its binding affinity with the enzyme. The obtained results could offer valuable insights into the mode of action of O. basilicum and can encourage the adoption of sustainable pest control practices that incorporate essential oils.
Assuntos
Inseticidas , Larva , Simulação de Acoplamento Molecular , Ocimum basilicum , Óleos Voláteis , Spodoptera , Animais , Ocimum basilicum/química , Spodoptera/efeitos dos fármacos , Larva/efeitos dos fármacos , Glutationa Transferase/metabolismo , Mariposas/efeitos dos fármacos , Monoterpenos Acíclicos , Cromatografia Gasosa-Espectrometria de MassasRESUMO
The tomato fruitworm Helicoverpa armigera (Hübner) is regarded as a serious pest that affects a great number of field crops globally. One of the environmentally safe alternatives to the utilization of insecticides is controlling H. armigera via the release of biological control agents by employing parasitoids, e.g., trichogrammatid species. One of the desired parasitoids indigenous to southwestern Iran is Trichogramma euproctidis (Girault). To anticipate the outcomes of augmentative releases of T. euproctidis in the field, the numerical and functional responses of female T. euproctidis that parasitizes the eggs of H. armigera were determined in the laboratory. The densities of host eggs per glass tube arena (length: 10 cm, diameter: 1 cm) were 2, 4, 8, 16, 32, 64, or 128 individuals. The functional response to the eggs of H. armigera indicated Holling's type II response. The estimated handling time and attack rate from the random parasitoid equation were 0.6898 h and 0.00823 h, respectively. This indicates that, at the maximum level, each T. euproctidis was capable of parasitizing 34.79 eggs a day. At the 128 host egg density, the number of eggs laid, that is, the numerical response, ascended as the density of host eggs increased up to a maximum of 89.90 eggs per female. According to the obtained results of the present investigation, T. euproctidis can serve as an appropriate candidate for augmentative biological control of H. armigera. Nevertheless, it is necessary to conduct complementary experiments in greenhouses and open fields.
Assuntos
Himenópteros , Inseticidas , Lepidópteros , Mariposas , Vespas , Feminino , Animais , Himenópteros/fisiologia , Agentes de Controle Biológico , Produtos Agrícolas , Óvulo , Vespas/fisiologiaRESUMO
Immature stages of insects are vulnerable to various antagonists, including pathogens. While the abiotic factors affecting pathogen prevalence in insect populations are reasonably well documented, much less is known about relevant ecological interactions. We studied the probability of the larvae of three lepidopteran species to die from fungal infection as a function of insect species and food plants in central Argentina. Local free-growing food plants were used to feed the lepidopteran larvae. The prevalence of entomopathogenic fungi remained low (about 5%), which is a value well consistent with observations on similar systems in other regions. Eight fungal species recorded, primarily belonging to Fusarium and Aspergillus, add evidence to the reconsideration of the nutritional modes in these genera in distinguishing the role of some species (complexes) to cause insect infections. Food plant species were found to have a substantial effect on the prevalence of entomopathogenic fungi. This was especially clear for the most abundant fungal species, a representative of the Fusarium fujikuroi complex. Feeding on a particular plant taxon can thus have a specific fitness cost. Compared to the data collected from Northern Europe, the Argentinian assemblages from the families Aspergillaceae and Nectriaceae overlapped at the genus level but did not share species. It remains to be confirmed if this level of divergence in the composition of assemblages of entomopathogenic fungi among distant regions represents a global pattern.
RESUMO
Thraumata gen. nov. is described to accommodate three South American species, two previously placed in Phuphena Walker, 1858, namely Thraumata petrovna (Schaus, 1904), comb. nov. and Thraumata subvenata (Schaus, 1914), comb. nov.; and one, Thraumata peruviensia sp. nov., newly described from Peru. Although the larval biology is unknown, these species share several features that suggest their placement in Eriopinae and, as a consequence, a potential association with ferns (Pteridophyta) as larval host plants.
RESUMO
A summary of all taxonomic and nomenclatural changes to the check list of the Noctuoidea of North America north of Mexico since the last update published in 2015 is provided. A total of 64 changes are listed and discussed, consisting of 26 recently published changes and additions, and an additional 38 presented herein. One stat. n., one stat. rev., six syn. n., and two comb. n. are proposed for the first time. Orthimella Schmidt & Lafontaine nom. n. is proposed here as an objective replacement name for Himella Grote, 1874 [Noctuinae: Orthosiini], a junior homonym of Himella Dallas, 1852 [Hemiptera: Coreidae].
RESUMO
This study evaluated the parasitism of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on eggs of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) at different ages and densities. The rates of parasitism and emergence, the number of parasitoids emerged per egg and sex ratio of offspring were evaluated in both experiments. Eggs of H. armigera up to 36 hours provided greater parasitism and emergence of adults compared to eggs up to 60 hours old. The number of parasitoids, which emerged per host egg, was greater than one and the sex ratio remained around 80% of females, regardless of the egg development stage. Females of T. pretiosum responded with superior rates of parasitism, emergence and number of parasitoids per egg at the densities of 20 and 25 eggs of H. armigera. These results indicate that T. pretiosum parasite with superior performance in eggs of up to 36h of age and densities of 20 eggs per female day-1 in laboratory conditions. These results will help to establish the intervals between releases of parasitoids, aiming to control this pest, when adjusted with knowledge of the survival of the parasitoids in the field and in pest infestation.(AU)
Este trabalho avaliou o parasitismo de Trichogramma pretiosum Riley (Hymenoptera:Trichogrammatidae) em ovos de Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) em diferentesidades e densidades. As taxas de parasitismo e emergência, número de parasitoides emergidos por ovo erazão sexual dos descendentes foram avaliados em ambos os experimentos. Ovos de H. armigera de até 36horas proporcionaram maior parasitismo e emergência dos adultos em comparação com ovos com até 60horas de idade. O número de parasitoides, que emergiram por ovo hospedeiro, foi superior a 1 e a razãosexual permaneceu em torno de 80% de fêmeas, independentemente do estágio de desenvolvimento doovo. Fêmeas de T. pretiosum responderam com taxas superiores de parasitismo, emergência e número deparasitoides por ovo nas densidades de 20 e 25 ovos de H. armigera. Estes resultados indicam que T.pretiosum parasita com desempenho superior em ovos de até 36h de idade e densidades de 20 ovos porfêmea dia-1 em condições laboratoriais. Estes resultados ajudarão a estabelecer os intervalos entre asliberações de parasitoides, visando o controle desta praga, quando ajustado com o conhecimento dasobrevivência dos parasitoides no campo e na infestação de pragas.(AU)
Assuntos
Animais , Fatores Etários , Insetos/parasitologia , Controle Biológico de Vetores/métodosRESUMO
This study evaluated the parasitism of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on eggs of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) at different ages and densities. The rates of parasitism and emergence, the number of parasitoids emerged per egg and sex ratio of offspring were evaluated in both experiments. Eggs of H. armigera up to 36 hours provided greater parasitism and emergence of adults compared to eggs up to 60 hours old. The number of parasitoids, which emerged per host egg, was greater than one and the sex ratio remained around 80% of females, regardless of the egg development stage. Females of T. pretiosum responded with superior rates of parasitism, emergence and number of parasitoids per egg at the densities of 20 and 25 eggs of H. armigera . These results indicate that T. pretiosum parasite with superior performance in eggs of up to 36h of age and densities of 20 eggs per female day- 1 in laboratory conditions. These results will help to establish the intervals between releases of parasitoids, aiming to control this pest, when adjusted with knowledge of the survival of the parasitoids in the field and in pest infestation.
Este trabalho avaliou o parasitismo de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) em ovos de Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) em diferentes idades e densidades. As taxas de parasitismo e emergência, número de parasitoides emergidos por ovo e razão sexual dos descendentes foram avaliados em ambos os experimentos. Ovos de H. armigera de até 36 horas proporcionaram maior parasitismo e emergência dos adultos em comparação com ovos com até 60 horas de idade. O número de parasitoides, que emergiram por ovo hospedeiro, foi superior a 1 e a razão sexual permaneceu em torno de 80% de fêmeas, independentemente do estágio de desenvolvimento do ovo. Fêmeas de T. pretiosum responderam com taxas superiores de parasitismo, emergência e número de parasitoides por ovo nas densidades de 20 e 25 ovos de H. armigera. Estes resultados indicam que T. pretiosum parasita com desempenho superior em ovos de até 36h de idade e densidades de 20 ovos por fêmea dia-1 em condições laboratoriais. Estes resultados ajudarão a estabelecer os intervalos entre as liberações de parasitoides, visando o controle desta praga, quando ajustado com o conhecimento da sobrevivência dos parasitoides no campo e na infestação de pragas.
Assuntos
Interações Hospedeiro-Parasita , Parasitos , Controle Biológico de VetoresRESUMO
Helicoverpa armigera, one of the world's most destructive crop pests, was first documented in Brazil in 2013. Within a few months, this polyphagous insect had spread over the Northeast and Central-West of Brazil, causing great agricultural losses. With several reports of populations resistant to pesticides and Bt crops around the world, there is great concern about the spread of this pest in Brazil. There is confusion about the actual distribution of this species due to the high morphological similarity with the native corn earworm Helicoverpa zea, which may also coexist with H. armigera in the field. Our aims here were (i) to confirm its presence in the State of Minas Gerais, one of the most important agricultural regions in the country; and (ii) to assess the co-occurrence of this pest with the congeneric corn earworm H. zea. Using molecular screening, we confirmed the presence of H. armigera in Bt-crops of soybean and cotton, and non-Bt-crops of soybean, cotton and maize. Mixed infestations of H. armigera with H. zea were found in non-Bt maize (Viçosa, Southeastern Minas Gerais). These results highlight the need for adequate control strategies for H. armigera in Brazil, to deal with its polyphagous feeding habits, high dispersal capacity and possible risks of hybridization with congeneric species.
RESUMO
Schaus (1929: 49) described Boalda gyona in a monobasic genus known only from the holotype taken in Santa Catarina, Brazil. Biezanko et al. (1957) reported the species from Uruguay. A number of specimens of Boalda similar to gyona were collected recently in Paraguay, at least two of which match the anomalous Argentinian taxon Nephelistis pulcherrima Köhler (1947: 77-78). Herein the genus Boalda is reviewed, with one new species described from the Paraguayan samples, and with N. pulcherrima transferred Boalda. A singleton specimen from Parque Nacional Cerro Corá, Dpto. Amambay, Paraguay, is figured but not described as a distinct species because of a lack of additional specimens.