Avaliação de fungos entomopatogênicos obtidos de diferentes ecossistemas brasileiros no controle biológico de Bemisia tabaci (Hemiptera: Aleyrodidae) e de Euschistus heros (Hemiptera: Pentatomidae)
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Data
2022-07-28
Autores
Gêa, Bianca Cristina Costa [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Euschistus heros (Hemiptera: Pentatomidae) e Bemisia tabaci (Hemiptera: Aleyrodidae) biótipo B, são pragas da soja, Glycine max, no Brasil. O controle de ambas as pragas é majoritariamente realizado com inseticidas químicos, mas há demanda pelo controle biológico, incluindo o microbiano. Os fungos entomopatogênicos têm vantagens devido ao modo de ação, variabilidade genética e permanência no ambiente. Assim, o estudo teve por objetivo isolar e identificar fungos entomopatogênicos obtidos de solos dos estados de SP, PR e MA, avaliando a patogenicidade dos microrganismos sobre E. heros e B. tabaci. Os fungos foram obtidos pelo “Bait Method” com larvas de Tenebrio molitor (Coleoptera: Tenebrionidae), alocados em potes com 50 g de solo. Os insetos mortos foram coletados diariamente e mantidos em câmara úmida para isolamento dos fungos, posteriormente foram preservados pelo método de Castellani e identificados por caracterização morfológica e molecular. Os testes de patogenicidade foram feitos em ovos, ninfas de 3º ínstar e adultos de E. heros e em ninfas de 4° ínstar de B. tabaci, com isolados que apresentaram viabilidade acima de 90%. Uma alíquota de 127 μl de cada suspensão fúngica na concentração de 1x108 conídios/mL, com 0,01% de Tween 80, foi aplicada com aerógrafo a 10 psi de pressão em cada placa de Petri contendo cinco ovos ou quatro ninfas/adultos de percevejo marrom ou dez ninfas de mosca-branca. O controle consistiu em água destilada autoclavada com 0,01% de Tween 80. Os experimentos com E. heros permaneceram em sala, a 25°C e UR de 80%, e foram avaliados diariamente por 15 dias, enquanto que os experimentos com a B. tabaci permaneceram por oito dias sob condições controladas em câmara tipo BOD (Temp. de 25 ± 1 °C e fotofase de 12 h). Os insetos foram avaliados diariamente, e levados para câmara úmida, favorecendo a esporulação. Foram identificados 28 isolados de Metarhizium anisopliae, 10 de Beauveria bassiana, sete de M. robertsii, três de Purpureocillium lilacinum, dois do gênero Cordyceps e um M. guizhouense. Foram avaliados 25 isolados em adultos e 28 em ninfas e ovos, nos testes de patogenicidade contra o percevejo marrom. Os mais patogênicos foram os isolados LCBPF 11, 19, 20 e 28, além do produto comercial Octane® para adultos, LCBPF 23, 77, 79, 80 e 82 para as ninfas de terceiro ínstar e LCBPF 08, 13, 63 e 81, além do produto comercial Octane® para os ovos. Para a mosca-branca, foram avaliados 27 isolados, se destacando o LCBPF 23 de B. bassiana, LCBPF 11 de C. javanica, LCBPF 02 de C. amoene-rosea e LCBPF 15 de B. bassiana, com eficiência de 100%, 100%, 95% e 95%, respectivamente. Sendo assim, os fungos entomopatogênicos apresentaram potencial de controle para ambas as pragas.
Euschistus heros (Hemiptera: Pentatomidae) and Bemisia tabaci (Hemiptera: Aleyrodidae) Biotype B, are pests of soybean, Glycine max, in Brazil. The control of both pests is mostly carried out with chemical insecticides, but there is a demand for biological control, including microbial control. Entomopathogenic fungi have advantages due to their mode of action, genetic variability and permanence in the environment. Thus, the study aimed to isolate and identify entomopathogenic fungi obtained from soils in the states of SP, PR and MA, evaluating the pathogenicity of microorganisms on E. heros and B. tabaci. The fungi were obtained by the “Bait Method” with larvae of Tenebrio molitor (Coleoptera: Tenebrionidae), placed in pots containing 50 g of soil. Dead insects were collected daily and kept in a humid chamber for the isolation of fungi, preserved by the Castellani method and identified by morphological and molecular characterization. Pathogenicity tests were performed on eggs, 3rd instar nymphs and adults of E. heros and on 4th instar nymphs of B. tabaci, with strains that showed viability above 90%. An aliquot of 127 μl of each fungal suspension at a concentration of 1x108 conidia mL-1 , with 0.01% Tween 80, was applied with an airbrush at 10 psi pressure in each Petri dish containing five eggs or four brown stink bug nymphs/adults or ten whitefly nymphs. The control was performed with autoclaved distilled water with 0.01% Tween 80. The experiments with E. heros were kept in a room at 25°C and 80% RH, and were evaluated daily for 15 days, while the experiments with the B. tabaci remained during eight days under controlled conditions in a BOD-type chamber (25 ± 1 °C and 12 h photophase). The insects were evaluated daily and taken to a humid chamber to improve sporulation. Twenty-eight strains of Metarhizium anisopliae, 10 of Beauveria bassiana, seven of M. robertsii, three of Purpureocillium lilacinum, two of the genus Cordyceps and one of M. guizhouense were identified. Were evaluated 25 strains in adults and 28 in nymphs and eggs, in the pathogenicity tests against the brown stink bug and the most pathogenic were the strains LCBPF 11, 19, 20 and 28, in addition to the commercial product Octane® for adults, LCBPF 23, 77, 79, 80 and 82 for 3rd instar nymphs and LCBPF 08, 13, 63 and 81, in addition to the commercial product Octane® for eggs. For the whitefly, 27 strains were evaluated, especially LCBPF 23, LCBPF 11, LCBPF 02 and LCBPF 15, with 100, 100, 95 and 95% of efficiency, respectively. Thus, the entomopathogenic fungi showed control potential for both pests.
Euschistus heros (Hemiptera: Pentatomidae) and Bemisia tabaci (Hemiptera: Aleyrodidae) Biotype B, are pests of soybean, Glycine max, in Brazil. The control of both pests is mostly carried out with chemical insecticides, but there is a demand for biological control, including microbial control. Entomopathogenic fungi have advantages due to their mode of action, genetic variability and permanence in the environment. Thus, the study aimed to isolate and identify entomopathogenic fungi obtained from soils in the states of SP, PR and MA, evaluating the pathogenicity of microorganisms on E. heros and B. tabaci. The fungi were obtained by the “Bait Method” with larvae of Tenebrio molitor (Coleoptera: Tenebrionidae), placed in pots containing 50 g of soil. Dead insects were collected daily and kept in a humid chamber for the isolation of fungi, preserved by the Castellani method and identified by morphological and molecular characterization. Pathogenicity tests were performed on eggs, 3rd instar nymphs and adults of E. heros and on 4th instar nymphs of B. tabaci, with strains that showed viability above 90%. An aliquot of 127 μl of each fungal suspension at a concentration of 1x108 conidia mL-1 , with 0.01% Tween 80, was applied with an airbrush at 10 psi pressure in each Petri dish containing five eggs or four brown stink bug nymphs/adults or ten whitefly nymphs. The control was performed with autoclaved distilled water with 0.01% Tween 80. The experiments with E. heros were kept in a room at 25°C and 80% RH, and were evaluated daily for 15 days, while the experiments with the B. tabaci remained during eight days under controlled conditions in a BOD-type chamber (25 ± 1 °C and 12 h photophase). The insects were evaluated daily and taken to a humid chamber to improve sporulation. Twenty-eight strains of Metarhizium anisopliae, 10 of Beauveria bassiana, seven of M. robertsii, three of Purpureocillium lilacinum, two of the genus Cordyceps and one of M. guizhouense were identified. Were evaluated 25 strains in adults and 28 in nymphs and eggs, in the pathogenicity tests against the brown stink bug and the most pathogenic were the strains LCBPF 11, 19, 20 and 28, in addition to the commercial product Octane® for adults, LCBPF 23, 77, 79, 80 and 82 for 3rd instar nymphs and LCBPF 08, 13, 63 and 81, in addition to the commercial product Octane® for eggs. For the whitefly, 27 strains were evaluated, especially LCBPF 23, LCBPF 11, LCBPF 02 and LCBPF 15, with 100, 100, 95 and 95% of efficiency, respectively. Thus, the entomopathogenic fungi showed control potential for both pests.
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Biocontrole, Beauveria, controle microbiano, Cordyceps, mosca-branca, Metarhizium, percevejo marrrom, prospecção, brown stink bug, microbial contro, whitefly, prospection