Biologia 67/5: 966—972, 2012 Section Zoology DOI: 10.2478/s11756-012-0086-x
Pathogens of bark beetles (Curculionidae: Scolytinae) and other beetles in Bulgaria
Danail Ilchev Takov1, Danail Dimitrov Doychev2, Andreas Linde3, Slavimira Atanasova Draganova4 & Daniela Kirilova Pilarska1,5
1Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 1, Tsar Osvoboditel Blvd., Sofia 1000, Bulgaria; e-mail: [email protected] 2University of Forestry, 10, Kl. Ohridski Blvd., Sofia 1756,Bulgaria 3University of Applied Sciences Eberswalde, Alfred-M¨oller-Straße 1, 16225 Eberswalde, Germany 4Institute of Soil Science, Agrotechnologies and Plant Protection, 7 Shosse Bankya Str., 1080 Sofia, Bulgaria 5Faculty of Forestry and Wood Science, Czech University of Life Sciences, 129 Kamýcká str, CZ-16521 Prague 6, Suchdol, Czech Republic
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. Key words: beetle pathogens; Gregarina typographi; Chytridiopsis typographi; ItEPV; Beauveria bassiana; Isaria farinosa; Bulgaria
Introduction The study of diversity and role of insect pest pathogens is related to the development of environmen- Forests are very valuable biological resources and their tally friendly methods to control the pest mass out- conservation and sustainable development is the basis breaks. The aim is to maintain a low density of pest in for their long term use. Each year insects cause ma- forests and to reduce the damages, respectively. There- jor damage to forestry. The role of beetles is very im- fore, the control of their density contributes to the qual- portant in this respect, as they are a part of the for- itative forest management. est ecosystems and this way connected with particular In the present work we obtain new data about tree species through feeding preferences. Bark beetles pathogens of bark beetles and other forest Coleoptera (Curculionidae: Scolytinae) are insect pests with high from different trees species, in particular on their diver- economical importance; they can cause mass drying of sity, occurrence and infection levels. coniferous forest trees. Therefore their pathogen com- plex is intensively investigated during the last years. More than 30 species of bark beetles were investigated Material and methods and 35 protozoan and microsporidian species (Weiser Nine forest stands from different regions of Bulgaria have 1954, 1977; Purrini 1978; Wegensteiner et al. 1996; been investigated from April 2009 to October 2010. A to- H¨andel et al. 2003; Wegensteiner & Weiser 2004; Kere- tal of 818 individuals of beetles, belonging to 22 species selidze et al. 2010; Lukášová & Holuša 2011; Holuša et were collected from different parts of spruce trees (stem, leaves, seeds, under bark). All collected insects were trans- al. 2012; Michalková et al. 2012), seven fungal species ◦ (Landa et al. 2001; Jankevica 2004; Keller et al. 2004; ferred to the laboratory and kept refrigerated at 1–4 Cto Sosnowska et al. 2004; Wegensteiner 1992, 2004; Glare reduce movement and prevent horizontal transmission of any pathogens. After the dissections, fresh preparations of et al. 2008; Draganova et al. 2010) as well as many ne- the gonads, Malpighian tubules, fat body, and the entire matode species (R¨uhm 1956; Massey 1974; Poinar 1975; gut from the imago hosts were examined for the presence Nedelchev et al. 2008) have been detected. The infor- of pathogens under light microscopy (×160–400) according mation about pathogens of other forest beetle species to Wegensteiner et al. (1996). When pathogens were ob- is also scarce. served, Giemsa stained smears were made of the infected