The ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) uses innate and learned chemical cues to locate its host, larvae of the pine sawyer Monochamus alternatus (Coleoptera: Cerambycidae)
Keywords:
volatile hydrocarbon, experience, host location, biological controlAbstract
In Asia, the pine sawyer beetle Monochamus alternatus Hope (Coleoptera: Cerambycidae) is the most important vector of the pinewood nematode Bursaphelenchus xylophilus Steiner and Buhrer (Aphelenchida: Parasitaphelenchidae), the causal agent of pine wilt disease, and the ectoparasitoid Scleroderma guani Xiao et Wu (Hymenoptera: Bethylidae) is the most important natural enemy of this pest. Efficient host location is critical to parasitoid fitness, and chemical cues are key factors guiding the host searching process. This study was conducted to elucidate the odor cues guiding host location in S. guani and the impact of previous host experience on this behavior. Tests were conducted in which S. guani oriented to different odor resources associated with M. alternatus and its habitat, and components of these volatiles were analyzed with gas chromatography/mass spectrometry. Orientation to various odors also was investigated using adult S. guani subjected to different adult experiences. Female S. guani could easily distinguish M. alternatus larvae from other odor resources. Hydrocarbons were the main components of volatiles derived from M. alternatus larvae and were absent in volatiles from wood and frass associated with M. alternatus larvae. Female S. guani oriented most strongly to 1st and 3rd instars of M. alternatus. Prior experience of host odor without oviposition decreased orientation of S. guani towards the host, and the host used for rearing had no impact on subsequent odor orientation by adult S. guani. Volatile hydrocarbons emanating from host larvae might be the key to host location by adult S. guani, and experience with hosts appears to reinforce behavioral responses. The present results may be useful references for improving augmentative biological control using S. guani against M. alternatus and other forest pests.
Resumen
En Asia, el escarabajo cerambycido Monochamus alternatus Hope (Coleoptera: Cerambycidae) es el vector mas importante del nematodo Bursaphelenchus xylophilus Steiner and Buhrer (Aphelenchida: Parasitaphelenchidae), el agente causal de “pine wilt disease”, y el ectoparasitoide Scleroderma guani Xiao et Wu (Hymenoptera: Bethylidae) es el enemigo natural mas importante de este plaga. Localizacion eficiente del huesped es critical al capacidad biologica del parasitoide y indicaciones quimicas son factores claves guiando el proceso. Este estudio fue conducido para elucidar los claves guiando el proceso de localizacion de huesped por S. guani y el efecto de experiencia en este comportamiento. Pruebas fue cunducido en lo cual S. guani se oriento a varios olores associados con M. alternatus y su habitat y componentes de estes quimicas volatiles fue analizado por “gas chromatography/mass spectrometry.” Orientacion a varios olores fue tambien investigado usando adultos de S. guani condicionados con diferentes experiencias adultos. Hembras de S. guani pudieron distinguir olores de larvas de M. alternatus desde los otros ofrecidos. Hydrocarbones fuerone los componentes principales de compuestos volatiles derivado de larvas de M. alternatus y estos fueron aucente en volatiles de madera y excremento associado con aquellas larvas. Hembras de S. guani orientaron mas fuertamente a larvas de M. alternatus de primera y tercera etapa. Experiencia previa de olor de huespede sin opportunidad de postura reduciron orientacion de S. guani hasta olor de su huesped, y el huesped de crianza not tenia efecto en la orientacion de S. guani adultos hacia olores. Hydrocarbones volatiles emanando de larvas huespedes poderon ser clave en el proceso de localizacion be huesped por S. guani adultos y experiencia con huespedes aparece resforzar esta comportamiento. Los resultados actuales pueden ser referencias útiles para mejorar el aumento en el control biológico usando S. guani contra M. alternatus y otras plagas forestales.
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