Nematodes associated with the double‐spined bark beetleIps duplicatus(Coleoptera:Curculionidae) in centralEurope

Abstract

Ips duplicatus (Sahlberg) is an important forest pest in central Europe, but its nematode associates have seldom been studied. Therefore, nematodes associated with I. duplicatus were determined at three localities in the Czech Republic. The percentage of beetles with phoretic nematodes ranged from 18 to 65%. Micoletzkya buetschlii and other phoretic nematodes were found under elytra, on wings, and between body segments. The percentage of beetles with nematodes in the haemocoel ranged from 3 to 30%, and the nematodes included Contortylenchus diplogaster and Parasitylenchus cf. aculeatus. Juveniles of Parasitorhabditis obtusa (Fuchs 1915) were found in the intestines of 0-16% of the beetles. The most abundant species in I. duplicatus galleries were P. obtusa and M. buetschlii. Cryptaphelenchus sp., Parasitaphelenchus sp. and unidentified tylenchid juveniles also were found in the galleries. The percentage of beetles with nematodes was greater in the overwintering than in the offspring generation, and numbers of nematodes per gallery increased with gallery development.

Nematodes associated withIps cembrae(Coleoptera: Curculionidae): comparison of generations, sexes and sampling methods

“…The determined positive correlation between the number of beetles with phoretic nematodes and with mites documents a simple relationship that as the gallery develops a favourable environment arises for the reproduction of all the associated organisms. Stone and Simpson (1990) found the numbers of mites and nematodes per unit sampling area to be positively correlated with the development stage of Ips grandicollis (Eichhoff), and a similar trend has been recorded also in the case of I. duplicatus (Grucmanova et al 2014b). The finding of mites more frequently on beetles from traps only serves to document the phoretic relationships between bark beetles and certain mites.…”

“…Micoletzkya juveniles were found in clusters of up to 130 individuals under the elytra, on the wings and between body segments of I. cembrae. This nematode has also been found in (R€ uhm 1956;Tenkacova and Mituch 1986;Grucmanova et al 2014b). This species is a typical phoretic nematode which uses the bark beetle to colonize new environments.…”

“…These nematode species have been found in the haemocoel, intestines and Malpighian tubules of other Ips bark beetles, including I. acuminatus (Gyllenhal 1827), I. amitinus (Eichhoff 1871), I. sexdentatus (Borner 1776) and I. typographus. C. diplogaster, which was the species most frequently found in the haemocoel during the current study, and have also been associated with I. cembrae, I. duplicatus, I. sexdentatus and I. typographus (R€ uhm 1956;Tenkacova and Mituch 1986;Grucmanova et al 2014b). It is known that the haemocoels of individual beetles can be simultaneously infested with more than one genus of parasitic nematode (e.g.…”

“…This species had previously been found in the frass of galleries and intestines of I. cembrae, I. typographus and I. duplicatus (e.g. R€ uhm 1956;Tenkacova and Mituch 1986;Grucmanova et al 2014b). Micoletzkya juveniles were found in clusters of up to 130 individuals under the elytra, on the wings and between body segments of I. cembrae.…”

“…Nematodes associated with Ips cembrae are very similar to those associated with I. typographus and I. duplicatus (R€ uhm 1956;Tenkacova and Mituch 1986;Grucmanova et al 2014b) perhaps as a result of the similarity or absolute equivalence of the host trees (Pfeffer 1989). Transportation of the same nematode species by the bark beetle Pityogenes chalcographus (Linnaeus 1761), which naturally occurs on spruce, larch and pine, is also considered as a possibility (e.g.…”