Tick pathogenicity, thermal tolerance and virus infection in Tolypocladium cylindrosporum

Herrero N, Pérez R, Oleaga A, Zabalgogeazcoa I. 2011. Tick pathogenicity, thermal tolerance and virus infection in Tolypocladium cylindrosporum. Annals of Applied Biology 159:192-201. Tolypocladium cylindrosporum is a fungus which has been isolated from soil, from asymptomatic plants as an endophyte, and has been shown to be pathogenic to several species of arthropods. The objective of the present work was to study a collection of T. cylindrosporum strains in order to evaluate the characteristics of this fungus as a bioacaricide. The pathogenicity of five different strains of T. cylindrosporum was tested against two tick species, Ornithodoros erraticus and Ornithodoros moubata. Both tick species were susceptible to all the fungal strains. Mortality was greater for O. erraticus, and differed among the five developmental stages of the ticks tested, and among the fungal treatments. Mean mortality rates were close to 60% for O. erraticus, similar to those reported for other entomopathogenic fungi used for this purpose. The responses of eleven different strains of the fungus to 22oC and 30oC were also studied. Significant differences in temperature tolerance occurred among the strains, and growth inhibition was observed at 30oC. Several mycoviruses were found infecting five of the eleven strains. However, no clear relationship was found between the presence of viruses and fungal growth or pathogenicity.