Virulence of commercial strains of Beauveria bassiana and Metarhizium brunneum (Ascomycota: Hypocreales) against adult Xylosandrus germanus (Coleoptera: Curculionidae) and impact on brood

• Published in: Biological control Vol. 58; no. 2; pp. 121 - 126
• Main Authors: Castrillo, Louela A., Griggs, Michael H., Ranger, Christopher M., Reding, Michael E., Vandenberg, John D.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-08-2011
• Subjects: Ambrosia beetle; Ascomycota; Beauveria bassiana; Coleoptera; Curculionidae; Invasive insect; Metarhizium; Metarhizium brunneum; Microbial control; Mycoinsecticide; Xylosandrus; Xylosandrus germanus; Beauveria bassiana; Microbial control; Metarhizium brunneum; Ambrosia beetle; Mycoinsecticide; Invasive insect; Xylosandrus germanus
• ISSN: 1049-9644; 1090-2112
• DOI: 10.1016/j.biocontrol.2011.04.010

Broods produced by Xylosandrus germanus foundresses sprayed with Beauveria bassiana GHA (A) or Metarhizium brunneum F52 (B). Fungal infection was evidenced by the presence of melanotic spots and a change in color among larvae and pupae (A) and by the presence of mycelia or conidia among adult progeny (B). [Display omitted]
► Three mycoinsecticides were tested against ambrosia beetle Xylosandrus germanus. ► Beauveria bassiana Naturalis and Metarhizium brunneum F52 were more virulent than B. bassiana GHA against adult females. ► Spraying did not affect initial tunneling activity, but resulted in reduced numbers forming galleries and producing brood. ► Broods from treated females were smaller in size, and some had up to 100% of the progeny infected.
The ambrosia beetle Xylosandrus germanus (Coleoptera: Curculionidae) is an invasive pest with a wide host range and is a serious pest of orchards and nurseries in the eastern and midwestern US. In this study we evaluated the potential of entomopathogenic fungi Beauveria bassiana and Metarhizium brunneum (Ascomycota: Hypocreales) as control agents against this beetle. Three commercially available strains of these fungi were assayed against adult females to determine their virulence and impact on brood production. Among the three strains tested, B. bassiana Naturalis and M. brunneum F52 were more virulent than B. bassiana GHA. Mortality observed 6days post-spray was 6.7±6.7%, 60±5.8% and 61.7±7.9% for GHA, Naturalis and F52, respectively, at the highest dosage tested (approximately 600conidia/mm2). Inoculation of adult females did not affect their initial tunneling activity, but resulted in reduced numbers forming galleries and producing brood compared to controls. Broods from treated females were smaller in size, and some had up to 100% of the progeny infected. Infection was observed among all beetle life stages. These data show that the impact of inoculating adult females extends beyond their own survival and suggest that infection of offspring could also significantly affect beetle populations in the field.