Naturally-occurring entomopathogenic fungi on three bark beetle species (Coleoptera: Curculionidae) in Bulgaria

Abstract

Bark beetles (Coleoptera: Curculionidae: Scolytinae) belong to one of the most damaging groups of forest insects and the activity of their natural enemies - pathogens, parasitoids, parasites or predators suppressing their population density, is of great importance. Biodiversity of entomopathogenic fungi on bark beetles in Bulgaria has been investigated sporadically. The aim of this preliminary study was to find, identify and study morphological characteristics of fungal entomopathogens naturally-occurring in populations of three curculionid species - Ips sexdentatus Boern, Ips typographus (L.) and Dryocoetes autographus (Ratz.). Dead pest adults were found under the bark of Pinus sylvestris and Picea abies trees collected from forests in the Maleshevska and Vitosha Mountains. Fungal pathogens were isolated into pure cultures on SDAY (Sabouraud dextrose agar with yeast extract) and were identified based on morphological characteristics both on the host and in a culture. Morphological characteristics of the isolates were studied by phenotypic methods. The fungal isolates obtained from dead adults of Ips sexdentatus, Ips typographus and D. autographus were found to belong to the species Beauveria bassiana (Bals. - Criv.) Vuillemin, Beauveria brongniartii (Saccardo) Petch and Isaria farinosa (Holmsk.) Fries (anamorph Ascomycota, Sordariomycetes: Hypocreales, Cordycipitaceae). Morphological traits of the isolates are described.Potkornjaci (Coleoptera: Curculionidae: Scolytinae) pripadaju jednoj od najstetnijih grupa sumskih insekata, te je delovanje njihovih prirodnih neprijatelja, patogena, parazitoida, parazita i predatora od velikog znacaja. Biodiverzitet entomopatogenih gljiva koje se javljaju kod potkornjaka u Bugarskoj malo je istrazivan. Cilj ovog pocetnog ispitivanja bio je da se pronadju, odrede i prouce morfoloske karakteristike gljiva kao entomopatogena koji se javljaju u prirodnim populacijama tri vrste potkornjaka (Curculionidae) - Ips sexdentatus Boern, Ips typographus (L.) i Dryocoetes autographus (Ratz.). Uginuli adulti su prikupljeni ispod kore stabala Pinus sylvestris i Picea abies poreklom sa planina Melesevska i Vitosa. Patogene gljive su izolovane kao ciste kulture na podlozi SDAY (Sabouraud dextrose agar with yeast extract) i odredjene na osnovu morfoloskih osobina kako na domacinu, tako i u kulturi. Morfoloske osobine izolata proucavane su fenotipskim metodama. Izolati gljiva dobijeni sa uginulih adulta Ips sexdentatus, Ips typographus i D. autographus pripadaju vrstama Beauveria bassiana (Bals.-Criv.) Vuillemin, Beauveria brongniartii (Saccardo) Petch i Isaria farinosa (Holmsk.) Fries (anamorf Ascomycota, Sordariomycetes: Hypocreales, Cordycipitaceae). Dat je opis morfoloskih osobina izolata.