Characterization and virulence of Chilean Lecanicillium (Hypocreales: Cordycipitaceae) isolates on Cinara cupressi (Hemiptera: Aphididae)

Authors: MONTALVA, C. - University Of Chile; BATRA, M. - Slovak Academy Of Sciences; ROJAS, E. - Agricultural And Livestock Service; ARISMENDI, N. - University Of Concepcion; RODRIGUES, J. - Federal University Of Goias; VALENZUELA, E. - University Of Chile; Humber, Richard

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2017
Publication Date: 5/16/2017
Citation: Montalva, C., Batra, M., Rojas, E., Arismendi, N., Rodrigues, J., Valenzuela, E., Humber, R.A. 2017. Characterization and virulence of Chilean Lecanicillium (Hypocreales: Cordycipitaceae) isolates on Cinara cupressi (Hemiptera: Aphididae). Biocontrol. doi:10.1007/s10526-017-9817-9.

Interpretive Summary: This manuscript reports the discovery, isolation, identification (using both traditional and genomic approaches), and confirmation of pathogenicity for its native hosts of an unusual fungal pathogen affecting cypress aphids (a highly invasive and economically significant aphid pest of cypress trees) in southern Chile. Extensive comparisons of the Chilean fungi with other isolates of closely related fungi affecting aphids proved these cypress aphid fungi to be identifiable as Lecanicillium attenuatum, a comparatively little known species that is confirmed by genomic evidence to be distinct from a morphologically similar species, Lecanicillium muscarium, and to represent a fourth species in the very important and globally distributed Lecanicillium lecanii species complex. This paper presents the first reported discovery of L. attenuatum from the New World; until now this species has been known only from East Asia. This Chilean fungal pathogen is well suited for mass production and testing as a potential biological control agent that might be applied to populations of cypress aphids–which, to the advantage of the fungus, proliferate primarily as genetically identical clones–in a program of integrated pest management for cypress aphids that could also incorporate conventional chemical pesticides (while helping to manage or to retard the development of pest resistance to these insecticides).

Technical Abstract: The cypress aphid, Cinara cupressi, is considered to be one of the hundred most important invasive pests in the world. In Chile, it was first detected thirteen years ago, and its populations have been expanding throughout the country. In the course of a survey of entomopathogenic fungi of this pest in southern Chile, three isolates of entomopathogenic fungi were obtained from naturally infected individuals. In this study, we identified these isolates and evaluated their pathogenicity to the cypress aphid in laboratory bioassays. Two further species, Lecanicillium longisporum (strain ARSEF 5126) and Lecanicillium muscarium (strain ARSEF 5128), formulated in the mycoinsecticides Vertalec® and Mycotal®, respectively, were used as reference isolates. All the Chilean isolates were identified genomically as Lecanicillium attenuatum and were pathogenic to third instar C. cupressis nymphs inoculated with conidial suspensions under laboratory conditions. The Chilean isolates were uniformly more pathogenic to this host than were the ARSEF isolates. The Chilean isolate L-2 yielded the lowest overall lethal concentration (LC50), 3×105 conidia ml-1 at 4 days post-inoculation, and the shortest lethal time (LT50), 3.7 days after inoculation with 106 conidia ml-1. The results of these bioassays indicate that the Chilean isolates have considerable potential as microbial control agents of the cypress aphid.