Pathogens of bark beetles (Curculionidae: Scolytinae) and other beetles in Bulgaria

Abstract

Abstract:The presence and diversity of beetle pathogens associated with different tree species in Bulgaria was investigated. In total, 818 specimens belonging to 22 beetle species were examined. Pathogens occurred in 9 host species. The infections were found in the gut (virus, nematodes, protozoans, microsporidia) and haemolymph (nematodes) of the infected insects. The following pathogen species: ItEPV, Beauveria bassiana, B. brongniartii, Isaria farinosa, Gregarina typographi, Gregarina spp., Chytridiopsis typographi, Chytridiopsis sp., and nematodes were revealed. Insects with mycoses were mummified and filled up with fungal structures, formed pseudosclerotium. Most pathogens were established in bark beetles (Scolytinae). For the first time, the fungus B. bassiana was reported in Tomicus piniperda, Orthotomicus longicollis, O. erosus, X. spinole, Taphrorychus villifrons and Phylobius sp. in Bulgaria. We also present the first records of gregarines in O. longicollis, Acanthocinus aedilis, Rhagium inquisitor, Pyrochroa coccinea, and of the microsporidium Chytridiopsis sp. in O. longicollis.

Diversity and prevalence of entomopathogenic fungi (Ascomycota, Hypocreales) in epidemic populations of bark beetles (Coleoptera, Scolytinae) in spruce forests of the Tatra National Park in Slovakia

“…bassiana, B. caledonica, B. pseudobassiana and B. brongniartii (e.g. Landa et al 2001, Wegensteiner 2007, Draganova et al 2010, Takov et al 2012, Mudrončeková et al 2013, Wegensteiner et al 2015a, Barta et al 2018a. In the current survey, we recorded all of them except for B. brongniartii, which is a well-known parasite of coleopteran larvae living in soil (Zimmermann 2007).…”

“…During the past two decades the occurrence of EPF in bark beetle populations has been documented in Europe in several studies (e.g. Landa et al 2001, Kreutz et al 2004, Wegensteiner 2007, Draganova et al 2010, Takov et al 2012, Mudrončeková et al 2013, Wegensteiner et al 2015a, Barta et al 2018a and Beauveria species have been reported as common pathogens.…”

Extremely low infection levels of pathogens and nematodes in Trypodendron spp. (Coleoptera: Curculionidae)

“…and a gregarine Gregarina cf. typographi commonly occur in the midgut of a number of representatives of the Scolytinae subfamily, and their infection level varies greatly among sites (Takov et al 2007;Holuša et al 2009;Takov et al 2010). Chytridiopsis typographi [(Weiser, 1954) Weiser, 1970] also occurs in many species of bark beetles (Haidler 1998;Händel et al 2001) and is apparently a non-specific pathogen in the intestine of a number of pests in coniferous stands (Wegensteiner 2004).…”

Infectious and parasitic diseases of phytophagous insect pests in the context of extreme environmental conditions

“…Several species of hypocrealean entomopathogenic fungi can be identified from field-collected bark beetles and Beauveria species are usually predominant ones (Landa et al 2001;Kreutz et al 2004a;Wegensteiner 2007;Draganova et al 2010Draganova et al , 2017Mudrončeková et al 2013;Wegensteiner et al 2015a;Wegensteiner et al 2015b;Barta et al 2018a). For example, in Slovakia a majority (89%) of infected I. typographus adults collected in forests were killed with Beauveria and only a minor part was infected with Isaria (8%) or Lecanicillium (3%) (Barta et al 2018a) ) Petch can also be detected (Takov et al 2012;Barta et al 2018a). Pathogenicity of Isaria species against bark beetles in laboratory bioassays is significantly lower when compared with B. bassiana (e.g.…”