Evaluation of Litchi chinensis for Host Status to Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae) and Susceptibility to Laurel Wilt Disease
Keywords:
Redbay ambrosia beetle, lychee, laurel wilt, Litchi chinensis, Raffaelea lauricolaAbstract
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), is an exotic wood-boring pest that vectors Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), the etiologic agent of laurel wilt. To date, all confirmed U.S. hosts of X. glabratus and suscepts of laurel wilt are members of the family Lauraceae. However, in previous research, an unknown variety of lychee, Litchi chinensis Sonn. (Sapindales: Sapindaceae), was found to be highly attractive to X. glabratus and elicited boring behaviors. Therefore, a study was undertaken to evaluate two commercial cultivars of lychee, ‘Brewster’ and ‘Mauritius’, for susceptibility to attack by X. glabratus, for transmission of R. lauricola, and for development of laurel wilt disease. In no-choice laboratory bioassays, 35 and 44% of females bored into cut bolts of ‘Mauritius’ and ‘Brewster’, respectively. Similar boring was observed on the trunks of two live ‘Brewster’ trees; but after 3 mo, there was no evidence of beetle reproduction, no symptoms of laurel wilt, and no recovery of R. lauricola from tissue associated with beetle galleries. Lychee trees artificially inoculated with an isolate of R. lauricola (RL4) that kills lauraceous hosts of this pathogen were asymptomatic after 1 mo, and assays for R. lauricola were negative. Chemical analysis indicated that lychee emits several sesquiterpene constituents in common with the Lauraceae, but at lower levels. Based on these data, we conclude that L. chinensis, although attractive to female X. glabratus, is not a likely reproductive host. This may be due to the inability of lychee wood to support growth of R. lauricola, the presumed primary nutritional symbiont of X. glabratus.
El escarabajo del laurel rojo, Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae), es un barrenador exotico que actua como vector de Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva (Ophiostomatales: Ophiostomataceae), el agente causal del secamiento del laurel. Hasta el presente, todos los hospederos de X. glabratus en USA han sido miembros de la familia Lauraceae. Sinembargo, en investigaciones realizadas anteriormente, se encontro que X. glabratus era muy atraido a litchi, Litchi chinesis Sonn. (Sapindales: Sapindaceae), y que el escarabajo mostraba comportamiento de barrenador de esta planta. En consecuencia, se comenzaron estudios para evaluar la susceptibilidad de dos variedades de litchi, “Brewster” y “Mauritius” al ataque de X. glabratus, la transmission de R. lauricola y el desarrollo de la enfermedad del laurel. En pruebas de laboratorio tipo no-eleccion, el 35 y 44% de hembras barrenaron secciones de troncos de “Mauritius” y “Brewster”. Similarmente, se observo barrenamiento de tallos de dos arboles de “Brewster”, pero despues de 3 meses, no hubo evidencia ni de reproduccion del escarabjo, ni de sintomas de secamiento del laurel, ni se aislo R. lauricola del los tuneles perforados por el escarabajo. Arboles de litchi fueron inoculados artificialmente con una cepa virulenta de R. lauricola (RL4) pero despues de un mes no mostraron sintomas de la enfermedad y pruebas de laboratorio demostraron que no se recupero R. lauricola de estos tejidos. Analisis de laboratorio indicaron que la madera del litchi emite en niveles bajos, varios volatiles de sequiterpenos los cuales son tambien comunes a los encontrados en plantas de la familia Lauraceae. Basados en estos datos, concluimos que aunque las hembras de X. glabratus son bastante atraidas a L. chinensis, este no es un hospedero donde se puedan reproducir. Esto es debido aparentemente a que R. lauricola que aprentemente es el simbionte nutricional primario de X. glabratus no puede crecer en la madera de litchi.
Downloads
Published
Issue
Section
License
Copyright for any article published in Florida Entomologist is held by the author(s) of the article. Florida Entomologist is an open access journal. Florida Entomologist follows terms of the Creative Commons, Attribution Non-Commercial License (cc by-nc). By submitting and publishing articles in Florida Entomologist, authors grant the FOJ and Florida Entomologist's host institutions permission to make the article available through Internet posting and electronic dissemination, and to otherwise archive the information contained both electronically and in a hard printed version. When used, information and images obtained from articles must be referenced and cited appropriately. Articles may be reproduced for personal, educational, or archival purposes, or any non-commercial use. Permission should be sought from the author(s) for multiple, non-commercial reproduction. Written permission from the author(s) is required for any commercial reproduction.