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1.
PLoS One ; 16(8): e0242645, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34398898

RESUMO

Entomopathogenic nematodes (EPNs) have been successfully applied as biological control agents against above ground and soil stages of insect pests. However, for commercial application, it is crucial to mass culture these nematodes using in vitro liquid culture technology, as it is not attainable when using susceptible insects as hosts. Lobesia vanillana (Lepidoptera: Tortricidae) is regarded a sporadic pest of wine grapes in South Africa. The in vivo- and in vitro-cultured South African EPNs, Steinernema yirgalemense and Steinernema jeffreyense (Rhabditida: Steinernematidae), were evaluated against larvae and pupae of L. vanillana in laboratory bioassays. For larvae, high mortality was observed for all treatments: In vitro-cultured S. yirgalemense (98%) performed better than S. jeffreyense (73%), while within in vivo cultures, there was no difference between nematode species (both 83%). No significant difference was detected between in vivo- and in vitro cultures of the same nematode species. The LD50 of the in vitro-cultured S. yirgalemense, was 7.33 nematodes per larva. Mortality by infection was established by dissecting L. vanillana cadavers and confirming the presence of nematodes, which was > 90% for all treatments. Within in vitro cultures, both S. yirgalemense and S. jeffreyense were able to produce a new cohort of infective juveniles from L. vanillana larvae. Pupae, however, were found to be considerably less susceptible to EPN infection. This is the first study on the use of EPNs to control L. vanillana. The relative success of in vitro-cultured EPN species in laboratory assays, without any loss in pathogenicity, is encouraging for further research and development of this technology.


Assuntos
Insetos/parasitologia , Mariposas/parasitologia , Rabditídios/patogenicidade , Animais , Agentes de Controle Biológico/administração & dosagem , Laboratórios , Larva/parasitologia , Controle Biológico de Vetores/métodos , Pupa/parasitologia , Solo/parasitologia , África do Sul
2.
PLoS Pathog ; 17(6): e1009656, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34125872

RESUMO

The exopolysaccharide galactosaminogalactan (GAG) has been well characterized in Aspergilli, especially the human pathogen Aspergillus fumigatus. It has been found that a five-gene cluster is responsible for GAG biosynthesis in Aspergilli to mediate fungal adherence, biofilm formation, immunosuppression or induction of host immune defences. Herein, we report the presence of the conserved GAG biosynthetic gene cluster in the insect pathogenic fungus Metarhizium robertsii to mediate either similar or unique biological functions. Deletion of the gene cluster disabled fungal ability to produce GAG on germ tubes, mycelia and appressoria. Relative to the wild type strain, null mutant was impaired in topical infection but not injection of insect hosts. We found that GAG production by Metarhizium is partially acetylated and could mediate fungal adherence to hydrophobic insect cuticles, biofilm formation, and penetration of insect cuticles. In particular, it was first confirmed that this exopolymer is responsible for the formation of appressorium mucilage, the essential extracellular matrix formed along with the infection structure differentiation to mediate cell attachment and expression of cuticle degrading enzymes. In contrast to its production during A. fumigatus invasive growth, GAG is not produced on the Metarhizium cells harvested from insect hemocoels; however, the polymer can glue germ tubes into aggregates to form mycelium pellets in liquid culture. The results of this study unravel the biosynthesis and unique function of GAG in a fungal system apart from the aspergilli species.


Assuntos
Interações Hospedeiro-Parasita/fisiologia , Metarhizium/metabolismo , Metarhizium/patogenicidade , Polissacarídeos/metabolismo , Virulência/fisiologia , Animais , Drosophila melanogaster/parasitologia , Proteínas Fúngicas/metabolismo , Mariposas/parasitologia
3.
PLoS One ; 16(6): e0253287, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34125871

RESUMO

The egg parasitoid Trichogramma evanescens Westwood is considered as an efficient biological control agent for managing several lepidopteran pests and it is widely distributed throughout the world. Mass rearing protocols of parasitoids that are currently in use in biocontrol programs require a meticulous quality control plan, in order to optimize their efficacy, but also their progeny production capacity. In this paper, the effect of different factors on the quality control in mass rearing of T. evenescens, using Plodia interpunctella (Hübner) and Galleria mellonella L. as host species, were investigated. The impact of egg agewas significant in the rates of parasitism, for both host species tested. Significantly highest percent of parasitoid emergence was noticed in two day-old eggs for both host species, while one day-old eggs day exhibited the maximum emergence when both species were used togetherin the same trials. Age-dependent storage egg preservation at either 4 or 9°C significantly influenced the parasitism percentages on both species. The highest parasitism percentage was recorded in two day-old G. mellonella eggs that are kept for 15 days at 9°C while the lower in one day-old P. interpunctella eggs for 60 d storage. Moreover, the highest parasitoid mortality was recorded in T. evanescens reared either on P. interpunctella or G. mellonella at 20°C. Rearing of the parasitoid on a mixture of eggs of both host species resulted in higher parasitism, but not always in higher rates of parasitoid emergence. The results of the present work provide useful information that can be further utilized in rearing protocols of T. evanescens.


Assuntos
Criopreservação , Himenópteros/genética , Controle Biológico de Vetores , Simbiose/genética , Animais , Agentes de Controle Biológico , Ovos/parasitologia , Especificidade de Hospedeiro/genética , Himenópteros/patogenicidade , Lepidópteros/parasitologia , Lepidópteros/patogenicidade , Mariposas/parasitologia , Vespas/parasitologia
4.
Arch Insect Biochem Physiol ; 107(2): e21786, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33818830

RESUMO

Cotesia kariyai (Ck) larvae implanted into the body cavity of the Mythimna separata (armyworm) larvae get melanized and encapsulated after adhesion by hemocytes called hyperspread cells (HSCs). The present study showed that HSCs could not adhere to the implanted Ck larvae in armyworm larvae after injection of Ck polydnavirus (CkPDV) + venom (V), thus melanization and encapsulation could not occur. A C-type lectin called Mys-IML of the host armyworm larvae was considered to be involved in the recognition of foreign substances which always expressed in hemocytes. The CkPDV DNA encodes a C-type lectin called Cky811 that has high amino acid homology to Mys-IML. HSCs did not adhere when CkPDV + V was mixed with the hemolymph of armyworm larvae on glass slides and incubated in vitro, but the addition of anti-Cky811 antibody enabled HSCs to adhere. The messenger RNA (mRNA) expression of Mys-IML in armyworm larvae injected with CkPDV + V became undetectable by 6 h. On the contrary, Cky811 mRNA was well expressed in the hemocytes of armyworm larvae injected with CkPDV + V from 0.5 to 6 h. Cky811 protein was also detected in the crude extracts from Ck venom gland + Ck venom reservoir, suggesting that these proteins regulate foreign substance recognition by the armyworm within 0.5 h. These results suggest that CkPDV + V suppresses mRNA expression of Mys-IML, and that Cky811 protein expressed in hemocytes regulates foreign substance recognition of Mys-IML, resulting in inhibition of the downstream reaction steps: HSCs adhesion, melanization, and encapsulation.


Assuntos
Lectinas Tipo C/imunologia , Mariposas/parasitologia , Polydnaviridae , Vespas , Animais , Anticorpos Antivirais/metabolismo , Hemócitos/imunologia , Hemócitos/metabolismo , Interações Hospedeiro-Parasita/imunologia , Imunidade , Larva/imunologia , Larva/metabolismo , Larva/parasitologia , Lectinas Tipo C/metabolismo , Mariposas/imunologia , Polydnaviridae/metabolismo , Proteínas Virais/imunologia , Proteínas Virais/metabolismo , Vespas/patogenicidade , Vespas/virologia
5.
Sci Rep ; 11(1): 8990, 2021 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-33903703

RESUMO

Therophilus javanus (Bhat & Gupta) is an exotic larval endoparasitoid newly imported from Asia into Africa as a classical biological control agent against the pod borer Maruca vitrata (Fabricius). The parasitoid preference for the five larval instars of M. vitrata and their influence on progeny sex ratio were assessed together with the impact of larval host age at the time of oviposition on development time, mother longevity and offspring production. In a choice situation, female parasitoids preferred to oviposit in the first three larval instars. The development of immature stages of the parasitoid was observed inside three-day-old hosts, whereby the first two larval instars of T. javanus completed their development as endoparasites and the third larval instar as ectoparasite. The development time was faster when first larval instars (two- and three-day-old) of the host caterpillars were parasitized compared to second larval instar (four-day-old). The highest proportion of daughters (0.51) was observed when females were provided with four-day-old hosts. The lowest intrinsic rate of increase (r) (0.21 ± 0.01), the lowest rate of increase (λ) (1.23 ± 0.01), and the lowest net reproductive rate (Ro) (35.93 ± 6.51) were recorded on four-day-old hosts. These results are discussed in the light of optimizing mass rearing and release strategies.


Assuntos
Mariposas/parasitologia , Controle Biológico de Vetores , Vespas/fisiologia , Animais , Feminino , Larva/parasitologia , Masculino , Reprodução
6.
Naturwissenschaften ; 108(2): 13, 2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33760987

RESUMO

Host preference behavior can result in adaptive advantages with important consequences for the fitness of individuals. Hopkin's host-selection principle (HHSP) suggests that organisms at higher trophic levels demonstrate a preference for the host species on which they developed during their own larval stage. Although investigated in many herbivorous and predatory insects, the HHSP has, to our knowledge, never been tested in the context of insects hosting selfish endosymbiotic passengers. Here, we investigated the effect of infection with the facultative bacterial symbiont Wolbachia on post-eclosion host preference in the parasitoid wasp Trichogramma brassicae (Hymenoptera: Trichogrammatidae). We compared host preference in Wolbachia-infected individuals and uninfected adult female parasitoids after rearing them on two different Lepidopteran hosts, namely the flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) or the grain moth Sitotroga cerealella (Lepidoptera: Gelechiidae) in choice and no choice experimental design (n = 120 wasps per each choice/no choice experiments). We showed that in T. brassicae, Wolbachia affects the post-eclosion host preference of female wasps. Wolbachia-infected wasps did not show any host preference and more frequently switched hosts in the laboratory, while uninfected wasps significantly preferred to lay eggs on the host species they developed on. Additionally, Wolbachia significantly improved the emergence rate of infected wasps when reared on new hosts. Altogether, our results revealed that the wasp's infection with Wolbachia may lead to impairment of post-eclosion host preference and facilitates growing up on different host species. The impairment of host preference by Wolbachia may allow T. brassicae to shift between hosts, a behavior that might have important evolutionary consequences for the wasp and its symbiont.


Assuntos
Interações Hospedeiro-Parasita/fisiologia , Mariposas/parasitologia , Vespas/microbiologia , Wolbachia/fisiologia , Animais , Feminino
7.
J Helminthol ; 95: e15, 2021 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-33691817

RESUMO

The legume pod-borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae) (LPB), is an important insect pest of pigeon pea. Chemical pesticides are generally employed to manage this pest, but because of the soil residue issues and other environmental hazards associated with their use, biopesticides are also in demand. Another benign alternative is to use entomopathogenic nematodes (EPNs) to manage this vital pest. In the present study, the infectivity of ten native EPNs was evaluated against LPB by assessing their penetration and production in the LPB. The effectiveness of the promising EPNs against second-, third- and fourth-instar LPB larvae was also studied. Heterorhabditis sp. (Indian Agricultural Research Institute-Entomopathogenic Nematodes Rashid Pervez (IARI-EPN RP) 06) and Oscheius sp. (IARI-EPN RP 08) were found to be most pathogenic to LPB, resulting in about 100% mortality within 72 h, followed by Steinernema sp. (IARI-EPN RP 03 and 09). Oscheius sp. (IARI-EPN RP 04) was found to be the least pathogenic to LPB larva with 67% mortality. Maximum penetration was exhibited by Heterorhabditis sp. (IARI-EPN RP 06) followed by Oscheius sp. (IARI-EPN RP 08), whereas the lowest rate of penetration was exhibited by Oscheius sp. (IARI-EPN RP 01). The highest rate of production was observed with Oscheius sp. (IARI-EPN RP 08), followed by Oscheius sp. (IARI-EPN RP 04 and 10). Among the tested instars of the LPB larvae, second-instar larvae were more susceptible to EPNs, followed by third- and fourth-instar larvae. The results indicate that Heterorhabditis sp. (IARI-EPN RP 06) and Oscheius sp. (IARI-EPN RP 08) have a good potential to the manage LPB.


Assuntos
Cajanus , Mariposas , Controle Biológico de Vetores , Rabditídios , Animais , Mariposas/parasitologia , Mariposas/patogenicidade
8.
J Chem Ecol ; 47(3): 294-302, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33523390

RESUMO

Adoxophyes honmai, a serious pest of tea plants, prefers to lay eggs on mature tea leaves rather than young leaves. Here, we examined a hypothesis that Ascogaster reticulata, an egg-larval parasitoid of A. honmai, increases the likelihood of encountering host egg masses by searching mature tea leaves when host-derived cues are not available. In a dual-choice bioassay using a four-arm olfactometer, A. reticulata preferred odor from intact, mature leaves versus young leaves. Based on volatile analysis with gas chromatography-mass spectrometry (GC-MS), we identified 5 and 10 compounds from mature and young leaf volatiles, respectively. The 5 components in the extract from intact mature leaves included (Z)-3-hexenyl acetate, (E)-ß-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), and methyl salicylate. When each individual compound, or quaternary and quintenary blends of them, ratios of which were adjusted to match those of mature leaf volatiles, were provided, parasitoids preferred the full mixture and the quaternary blend devoid of DMNT to the solvent control. Methyl salicylate, one of the components of preferred blends, was not detected among young leaf volatiles. We concluded that the volatile composition of tea leaves changes, depending on their maturity, and that this composition affects foraging behavior of the parasitoid, which is closely related to the host herbivore's oviposition preference.


Assuntos
Camellia sinensis/química , Himenópteros/parasitologia , Odorantes/análise , Folhas de Planta/química , Compostos Orgânicos Voláteis/análise , Acetatos/análise , Acetatos/metabolismo , Monoterpenos Acíclicos/análise , Monoterpenos Acíclicos/metabolismo , Alcenos/análise , Alcenos/metabolismo , Animais , Camellia sinensis/metabolismo , Ecossistema , Cromatografia Gasosa-Espectrometria de Massas , Larva/parasitologia , Mariposas/parasitologia , Folhas de Planta/metabolismo , Salicilatos/análise , Salicilatos/metabolismo , Terpenos/análise , Terpenos/metabolismo
9.
Neotrop Entomol ; 50(1): 90-99, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33501636

RESUMO

A new species of Trichogramma Westwood (Hymenoptera: Trichogrammatidae) is described: Trichogramma foersteri sp. nov. Takahashi from eggs of Anticarsia gemmatalis Hübner, (Lepidoptera: Erebidae) a major soybean defoliating pest. The parasitoid was collected in São José dos Pinhais, Paraná State, Brazil, and molecular and morphological characters were used to confirm the identity of the new species. Preliminary biological data are provided to demonstrate its high capacity of parasitism. The new species is a potential candidate as a biological control agent against some lepidopteran-pests.


Assuntos
Mariposas/parasitologia , Vespas/anatomia & histologia , Vespas/classificação , Animais , Brasil , Feminino , Masculino , Óvulo/parasitologia , Soja
10.
Parasit Vectors ; 14(1): 45, 2021 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-33436058

RESUMO

BACKGROUND: Steinernema feltiae is an entomopathogenic nematode used in biological control programs with a global distribution. Populations of this species show phenotypic plasticity derived from local adaptation and vary in different traits, such as location and host penetration. The aim of this work was to describe a Chilean isolate of this nematode species, using integrative approaches. METHODS: Nematode morphological and morphometric studies were conducted along with molecular analysis of nuclear genes. The symbiotic bacterium was also identified by sequencing the 16S rRNA gene. Some ecological characteristics were described, including the temperature requirements for the nematode life cycle and the effect of soil water content for optimal reproduction. RESULTS: Morphometric characterization revealed a large intra-specific variability. The isolate identity was also corroborated with the analysis of nuclear genes. Based on the 16S gene, its symbiont bacteria, Xenorhabdus bovienii, was identified. The lowest, optimal and highest temperatures found to limit the infestation and reproduction on Galleria mellonella were 10, 20 and 30 °C, respectively; the emergence from the host larvae occurred approximately 10 days after inoculation. Differences were observed in offspring, and 120 infective juveniles (IJ)/larva was the most prolific dose at 20 °C. The soil water content did not affect the number of IJ invaders, penetration efficacy and IJ emergence time or offspring per larva, but it caused a delay in achieving full mortality at the permanent wilting point with respect to saturation and field capacity. CONCLUSIONS: For the first time, a Chilean isolate of S. feltiae is described in detail considering morphological, molecular and ecological aspects. The isolate was shown to be efficient in soil containing water, with optimal temperatures ranging from 15 to 25 °C for host infestation and production of an abundant offspring; these characteristics would allow its potential use as control agents in a wide geographical area of the country.


Assuntos
Rabditídios/genética , Rabditídios/isolamento & purificação , Animais , Chile , Feminino , Larva/parasitologia , Estágios do Ciclo de Vida , Masculino , Mariposas/parasitologia , Controle Biológico de Vetores , RNA Ribossômico 16S/genética , Rabditídios/anatomia & histologia , Rabditídios/classificação , Infecções por Rhabditida/parasitologia , Simbiose , Temperatura , Xenorhabdus/genética , Xenorhabdus/fisiologia
11.
Arch Insect Biochem Physiol ; 106(2): e21758, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33145828

RESUMO

Stress enhances the concentration of reactive oxygen species (ROS) in animal plasma. Increased ROS alter various physiological functions, such as development and the immune response, but excessive increases could be harmful. In this study, we tested the hypothesis that abnormally increased plasma ROS levels are associated with animal death. Injection of the nematode Caenorhabditis elegans into insect larvae caused high mortality in Galleria mellonella, and the plasma ROS concentration was four times higher than M9 buffer-injected larvae. There was no difference in plasma antioxidant activity after nematode injection. However, coinjecting nematodes with an antioxidant (ascorbic acid or N-acetylcysteine) suppressed increases in ROS concentrations by the nematodes and increases in the number of nematodes in the larvae, which increased G. mellonella survival. These results suggest that the abnormal elevation of ROS associated with the stress caused by nematode propagation is lethal for G. mellonella.


Assuntos
Interações Hospedeiro-Parasita , Mariposas/parasitologia , Nematoides/fisiologia , Espécies Reativas de Oxigênio/metabolismo , Animais , Larva/crescimento & desenvolvimento , Larva/parasitologia , Mariposas/crescimento & desenvolvimento , Plasma/parasitologia
12.
Insect Sci ; 28(1): 180-190, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31990456

RESUMO

Trichogramma brassicae (Bezdenko) is an important biological control agent that has been used widely against many lepidopteran pests. Commonly, colonies of Trichogramma are mass reared on factitious hosts such as Sitotroga cerealella (Olivier) over many generations. In this study, we evaluated the quality and performance of a colony of T. brassicae that had been reared for over 45 generations (G) using two-sex life table parameters and parasitism capacity. We found that female adult longevity was significantly different among sequential generations, ranging from 5.58 ± 2.5 d (at G5) to 3.75 ± 1.42 d (at G45). However, no significant difference was found in male adult longevity among different generations. Although female wasps survived longer until the 15th generation, they allocated more days for egg laying at G5 and G10. The highest values of gross reproductive rate (GRR), net reproductive rate (R0 ), intrinsic rate of increase (r), finite rate of increase (λ) and mean generation time (T) were found in G5 and G10, which also showed significantly higher c0 . No significant difference in the finite parasitism rate (ω) was found among generations up to G15. These results suggest that T. brassicae wasps held under continuous laboratory rearing can be used successfully in biological control programs until the 15th generation without any loss of quality or performance. However, laboratory mass rearing colonies declined in quality after 15 generations and we suggest that they should be rejuvenated regularly by adding field-collected parasitoids periodically.


Assuntos
Interações Hospedeiro-Parasita , Mariposas/parasitologia , Controle Biológico de Vetores , Controle de Qualidade , Vespas/fisiologia , Animais , Feminino , Tábuas de Vida , Longevidade , Masculino , Oviposição , Fatores Sexuais
13.
Bull Entomol Res ; 111(1): 91-99, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32613923

RESUMO

In the American continent, the sugarcane borer Diatraea saccharalis (F.) is the main pest in sugarcane producing areas. The objective of this study was to assess the effect of crop residue management on damage by D. saccharalis, its egg parasitoids and the ants associated with sugarcane. The study was carried out during 2011-2012, 2012-2013 and 2013-2014 crop cycles, in three commercial fields located in different regions of Tucumán state, Argentina. Two types of crop residue management (= treatments) were compared: conservation of trash at the soil surface (CT) and trash burning (TB). In 'trash conservation' treatment, crop residue was allowed to remain over the soil surface during the whole sugarcane growing season, while the second treatment consisted of complete burning of trash blanket approximately 2 weeks after harvest. The injury level was measured by recording the number of stalks bored and internodes bored. Parasitism was estimated by counting the total number of eggs and number of black eggs (which indicates the occurrence of egg parasitoids). Ants (Formicidae) richness was calculated by two estimators; abundance-based coverage estimator and incidence-based coverage estimator, using the non-parametric richness estimators: Chao 2 and Jackknife. Finally, the indicator value was estimated through the measurement of specificity and fidelity. In all the parameters studied no significant difference was found between TB and CT treatments.


Assuntos
Formigas/fisiologia , Produção Agrícola/métodos , Herbivoria , Mariposas/fisiologia , Mariposas/parasitologia , Saccharum , Animais , Argentina , Dípteros/fisiologia , Himenópteros/fisiologia , Larva/crescimento & desenvolvimento , Larva/fisiologia , Mariposas/crescimento & desenvolvimento , Óvulo/parasitologia , Saccharum/crescimento & desenvolvimento
14.
Bull Entomol Res ; 111(3): 357-363, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33331252

RESUMO

Tuta absoluta (Meyrick) is considered as a major pest of tomato worldwide that causes significant losses in the crop production. This study aimed to evaluate integration of two effective and environmentally safe methods (host plant resistant and biological control) for sustainable management of the pest under greenhouse conditions. The experiment was conducted based on the factorial design with ten replicates under greenhouse conditions (22 ± 3°C, 50 ± 10 RH and 14 L:10 D photoperiod). Infestation to T. absoluta was conducted at the first-flowering stage of the plants by introducing a pair of newly emerged adults (one female and one male) per plant. Ten days later, the biological agent, Trichogramma brassicae, was released on the treatments by hanging a card contained 50 parasitized eggs in each replicate. Observation was performed weekly on ratio of infested leaves per plant (%), number of larvae/plant, number of mines/leaf and ratio of infested fruits/plant (%). Results indicated that the susceptible variety alone (Izmir) supported the highest ratio of infested leaves (42.92 ± 1.95%), number of larvae/plant (12.86 ± 0.71), number of mines/leaf (1.29 ± 0.07) and infested fruits/plant (18.8 ± 1.10%), whereas the lowest (6.12 ± 0.42%, 1.85 ± 0.13, 0.18 ± 0.02 and 0.12 ± 0.06%, respectively) were observed in combined resistant variety (Cherry) and parasitoid released treatment. Integration of these methods not only decreases damage caused on tomato leaflets and fruits, but also reduces insecticide applications which are adversely impact human health and environment.


Assuntos
Himenópteros , Lycopersicon esculentum/fisiologia , Mariposas/parasitologia , Controle Biológico de Vetores/métodos , Defesa das Plantas contra Herbivoria , Animais , Fatores Biológicos , Inseticidas/farmacologia , Larva/parasitologia , Mariposas/efeitos dos fármacos , Parasitos , Plantas
15.
J Biosci ; 452020.
Artigo em Inglês | MEDLINE | ID: mdl-33361627

RESUMO

Tobacco is one of the major industrial crops cultivated worldwide. Chemical control is the main method employed to reduce damage by insect pests. The use of entomopathogenic fungi represents an alternative to replace insecticides. The search for effective strains in the field constitutes a first step when developing a formulation. The objective of this work was to study genetic differences among isolates of entomopathogenic fungi obtained from tobacco grown soils using ISSR markers. The pathogenicity of the strains towards Helicoverpa gelotopoeon and Diabrotica speciosa was also assessed in order to search for a relationship between virulence and genetic diversity. Nineteen isolates were identified according to morphological features and molecular techniques as Beauveria bassiana (11) and Purpureocillium lilacinum (8). The diversity tree generated by ISSR analysis showed a high diversity among the strains. The pathogenicity towards H. gelotopoeon and D. speciosa was assessed and the logistic models generated showed that B. bassiana isolates LPSc1215 and LPSc1364 were the most pathogenic against both insect pests tested. In the diversity tree, these strains were grouped in a same cluster with a similarity level of approximately 85%, indicating a possible relationship between virulence and the band pattern generated.


Assuntos
Fungos/genética , Controle Biológico de Vetores , Microbiologia do Solo , Tabaco/crescimento & desenvolvimento , Animais , Beauveria/genética , Beauveria/patogenicidade , Fungos/crescimento & desenvolvimento , Fungos/patogenicidade , Variação Genética/genética , Hypocreales/genética , Hypocreales/patogenicidade , Insetos/microbiologia , Insetos/parasitologia , Mariposas/microbiologia , Mariposas/parasitologia , Filogenia , Tabaco/microbiologia
16.
J Insect Sci ; 20(6)2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-33232487

RESUMO

Bacillus thuringiensis Berliner subsp. kurstaki (Btk) and Habrobracon hebetor Say are both biological control agents of Helicoverpa armigera Hubner. The present study evaluated their compatibility for combined application against this pest by examining the acceptability of Btk-inoculated hosts for H. hebetor females and testing for negative life-history impacts on developing progeny. Second-instar H. armigera larvae fed for 72 h on potted chickpea plants treated with three concentrations of Btk (LC15, LC35, and LC70) and were then used in bioassays of parasitoid development and parasitism behavior. Survival of parasitoids was significantly reduced, and immature development prolonged, on hosts fed chickpea plants treated with LC35 and LC70  Btk, but not on plants treated with LC15  Btk. Parasitoids failed to discriminate against hosts treated with LC15 or LC35  Btk in choice tests, but attacked fewer hosts treated with LC70  Btk, paralyzing and parasitizing more healthy hosts, and laying more eggs on them. In contrast, a no-choice test revealed that more hosts treated with LC35 and LC70  Btk were paralyzed compared with control or LC15-treated hosts, but the numbers of hosts parasitized and eggs laid did not vary among Btk treatments. Thus, females required an experience with healthy hosts, as they had in the choice test, to discriminate against diseased ones. We conclude that H. hebetor and Btk are compatible for joint application against H. armigera, which could potentially improve biological control of this pest.


Assuntos
Bacillus thuringiensis/química , Interações Hospedeiro-Parasita , Controle de Insetos , Mariposas/parasitologia , Controle Biológico de Vetores , Vespas/fisiologia , Animais , Feminino , Larva/crescimento & desenvolvimento , Larva/parasitologia , Mariposas/crescimento & desenvolvimento , Vespas/crescimento & desenvolvimento
17.
J Helminthol ; 94: e188, 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32907645

RESUMO

The potato tuber moth, Phthorimaea operculella (Zeller), is a serious pest of potato and other commercial crops belonging to the Solanaceae family. In recent years, it has become an emerging problem in potato-growing regions of the Nilgiri hills of southern India. It is responsible for the reduced quality and quantity of marketable potatoes. In this regard, the development of an eco-friendly control method for the management of the potato tuber moth is urgently required. Therefore, in the present study, the virulence of Steinernema cholashanense CPRSUS01 originally isolated from the potato rhizosphere was tested on fourth-instar larvae and pupae of P. operculella. Steinernema cholashanense caused the greatest mortality in the fourth-instar larval stage (100%) than the pupae (30%). In addition to this, penetration and reproduction of this nematode was also studied in fourth-instar larvae of P. operculella and this is the first report of penetration and reproduction of any entomopathogenic nematode species on potato tuber moth larvae. The reproduction capacity of S. cholashanense on P. operculella is higher (702 infective juveniles mg-1 body weight). Our results indicated that S. cholashanense has good potential as an alternative tool for the management of P. operculella. But before including S. cholashanense in the integrated pest management program of P. operculella, its efficacy should be tested under field conditions.


Assuntos
Mariposas/parasitologia , Controle Biológico de Vetores , Rabditídios/patogenicidade , Solanum tuberosum/parasitologia , Animais , Feminino , Índia , Larva/parasitologia , Doenças das Plantas/prevenção & controle , Pupa/parasitologia , Rabditídios/isolamento & purificação , Rizosfera
18.
Genome Biol Evol ; 12(12): 2554-2560, 2020 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-32946579

RESUMO

Busseola fusca (Fuller) (Lepidoptera: Noctuidae), the maize stalk borer, is a widespread crop pest in sub-Saharan Africa that has been the focus of biological research and intensive management strategies. Here, we present a comprehensive annotated transcriptome of B. fusca (originally collected in the Western Province of Kenya) based on ten pooled libraries including a wide array of developmental stages, tissue types, and exposures to parasitoid wasps. Parasitoid wasps have been used as a form of biocontrol to try and reduce crop losses with variable success, in part due to differential infectivities and immune responses among wasps and hosts. We identified a number of loci of interest for pest management, including genes potentially involved in chemoreception, immunity, and response to insecticides. The comprehensive sampling design used expands our current understanding of the transcriptome of this species and deepens the list of potential target genes for future crop loss mitigation, in addition to highlighting candidate loci for differential expression and functional genetic analyses in this important pest species.


Assuntos
Interações Hospedeiro-Parasita , Mariposas/genética , Controle Biológico de Vetores , Transcriptoma , Animais , Feminino , Larva/metabolismo , Masculino , Mariposas/metabolismo , Mariposas/parasitologia , Família Multigênica , Vespas/fisiologia , Zea mays
19.
J Invertebr Pathol ; 175: 107452, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32763230

RESUMO

Environmental factors such as temperature and desiccation impact the survival and efficacy of entomopathogenic nematodes (EPNs). Most studies on environmental tolerance have focused on EPNs applied in aqueous suspension. Another approach for EPN application is via infected host cadavers. Emergence in host cadavers is also more representative of nematodes in natural populations. In prior studies, certain advantages in fitness have been observed with the cadaver application approach relative to aqueous application, yet the impact of environmental stress on these approaches requires investigation. In this study, we compared the effects of various temperatures (heat and cold) and desiccation intervals (48 and 72 hr) on the survival, virulence and reproductive capacity of Heterorhabditis bacteriophora and Steinernema glaseri when applied via cadaver versus aqueous suspension. In the heat tolerance bioassays, following exposure to 30 °C, 35 °C and 37. 5 °C, nematodes (from both species) in the cadaver treatments exhibited higher survival, and reproductive capacity compared with aqueous application. No survival was observed above 37.5 °C regardless of species or application approach. In cold tolerance, no differences were observed between the cadaver and aqueous treatments after a sequence of exposures from 10 °C to -2 °C. In desiccation assays, following exposure to 85% relative humidity for 2 or 3 days, nematodes (from both species) exhibited higher survival and reproduction in the cadaver treatment than in the aqueous treatment, whereas no differences were observed in virulence. This is the first study to find differential stress tolerance among nematodes emerged from infected host cadavers versus those applied in aqueous suspension. Our findings indicate additional advantages when using the cadaver approach for biocontrol applications, and suggest EPNs existing in natural populations may have broader environmental tolerance than those applied via aqueous suspension.


Assuntos
Mariposas/parasitologia , Controle Biológico de Vetores , Strongyloidea/fisiologia , Animais , Cadáver , Meio Ambiente , Larva/crescimento & desenvolvimento , Larva/parasitologia , Mariposas/crescimento & desenvolvimento , Água
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