Effect of Mexican Hirsutella citriformis (Hypocreales: Ophiocordycipitaceae) strains on Diaphorina citri (Hemiptera: Liviidae) and the predators Chrysoperla rufilabris (Neuroptera: Chrysopidae) and Hippodamia convergens (Coleoptera: Coccinellidae)
Keywords:
huanglongbing, Asian citrus psyllid, biological control, non-target insectAbstract
Due to its role in the transmission of Candidatus Liberibacter asiaticus, a pathogen associated with huanglongbing, a catastrophic disease of citrus in the world, Diaphorina citri Kuwayama (Hemiptera: Liviidae) has become a very dangerous invasive pest. To contribute to increasing alternatives for its management, we evaluated against D. citri adults the pathogenicity of conidia and blastospores of 8 Mexican strains of the entomopathogenic fungus Hirsutella citriformis Speare (Hypocreales: Ophiocordycipitaceae). Furthermore, we conducted tests with non-target insects that included the predators Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) and Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae). Experiments in the laboratory included the application of the fungus by contact and through liquid sprays. Strains were collected from citrus areas of Mexico. They were grown in PDAY media and applied at 1 × 106 conidia per mL. All bioassays were conducted under controlled conditions at 26 ± 1 °C, a 16:8 h L:D photoperiod, and 76 ± 4% RH and maintained during 26 d after inoculation. Tests with D. citri were performed 3 times at different dates. Mean mortality by H. citriformis strains on D. citri adults ranged from 82 to 92%; INIFAP-Hir-1 strain produced the highest rate. Sprayed conidia produced 69% mortality. Use of sprayed blastospores caused 32 to 49 % mortality. LC50 obtained for INIFAP-Hir-1 strain was 3.4 × 106 conidia per mL. IB-Hir-1, IB-Hir-2, INIFAP-Hir-1, and INIFAP-Hir-2 strains inoculated by contact on H. convergens adults caused 9 to 11% mortality; in larvae of C. rufilabris, mortality ranged from 19 to 25%. In both tests, there were no statistical differences when compared with the untreated control. Unlike D. citri, all dead predator specimens showed absence of H. citriformis mycosis. The results suggest potential for the integration of this fungus in the management of D. citri. Data obtained from the predators could support safe use of this biological control agent.
Resumen
Debido a su función en la transmisión de Candidatus Liberibacter asiaticus, un patógeno asociado al Huanglongbing, una enfermedad catastrófica de los cítricos en el mundo, Diaphorina citri Kuwayama (Hemiptera: Liividae) se ha convertido en una plaga invasiva muy peligrosa. Para contribuir a incrementar las alternativas para su manejo, evaluamos la patogenicidad de conidias y blastosporas de 8 cepas mexicanas del hongo entomopatógeno Hirsutella citriformis Speare (Hypocreales: Ophiocordycipitaceae) contra adultos de D. citri; además realizamos pruebas contra insectos no blanco, los depredadores Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) y Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae). Los experimentos en laboratorio incluyeron aplicación del hongo por contacto y mediante aspersiones. Las cepas fueron colectadas en diferentes áreas citrícolas de México, cultivadas en medio PDAY y asperjadas a 1 × 106 conidia/mL; todos los bioensayos fueron conducidos bajo condiciones controladas a 26 ± 1 °C, 16:8 L:O, 76 ± 4% HR y mantenidos durante 26 días después de la inoculación; las pruebas contra D. citri fueron realizadas 3 veces en diferentes fechas. La mortalidad causada por H. citriformis contra adultos de D. citri fue 82-92%; la cepa INIFAP-Hir-1 registró el mayor porcentaje. Las conidias asperjadas produjeron 69% de mortalidad; mientras que el uso de blastosporas causó 32-49%. La CL50 obtenida para la cepa INIFAP- Hir-1 fue 3.4 × 106 conidias/mL. Las cepas IB-Hir-1, IB-Hir-2, INIFAP-Hir-1 e INIFAP-Hir-2 inoculadas por contacto contra adultos de H. convergens causaron 9-11% de mortalidad; en larvas de C. rufilabris fue de 19-25%; en ambas pruebas no existieron diferencias estadísticas con respecto al testigo. A diferencia de D. citri, todos los especímenes de depredadores muertos mostraron ausencia de micosis por H. citriformis. Los resultados sugieren potencial para la integración de este hongo en el manejo de D. citri; datos obtenidos de los depredadores podrían respaldar el uso seguro de este agente de control biológico.
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