Infecting Ips typographus (Coleoptera, Curculionidae) with Beauveria bassiana,Metarhizium anisopliae or Isaria fumosorosea (Ascomycota)

Abstract: Adult Ips typographus were inoculated with Beauveria bassiana, Metarhiziumanisopliae or Isaria fumosorosea alternatively by dipping the beetles directly into conidiosporesuspensions or by forcing them to walk on spore suspension treated spruce bark. Effect oftemperature was tested by incubating experiments at 15°C, 20°C or 25°C.Direct inoculation was successful with all three fungal species tested. Infection rates variedbetween the three fungal species (75.7%-8.1%) depending on incubation temperature. Infectionrate was significantly higher only with B. bassiana at 20°C compared to the other two fungusspecies. Mean life span was prolonged at 15° and shortest at 25°C with all three fungus species.Direct inoculation caused always higher infection rates and shorter mean life span comparedto indirect inoculation with all three fungal species. Limited contact with suspension treated barkresulted in successful infection, but duration of beetles’ contact with the conidia on barkinfluenced the infection success. Infection was highest when beetles had contact with freshlysuspension treated bark for three minutes with B. bassiana and I. fumosorosea at 20°C and forfive minutes with M. anisopliae at 25°C. Infection rates were significantly lower in most casesafter shorter contact with treated bark compare to shorter contact or testing beetles after one weekincubation of log sections compared to freshly treated bark.