Pine engraver beetle Ips acuminatus as a potential vector of Sphaeropsis sapinea

The pine engraver beetle Ips acuminatus Gyll. is a potential vector of the Sphaeropsis tip blight pathogen according to Leach’s postulates. The specimens of I. acuminatus were associated with numerous fungi species, namely Sphaeropsis sapinea (Fr.) Dyko & B. Sutton and ophiostomatoid species. The association between opportunistic pathogen S. sapinea and I. acuminatus has been confirmed for 62.9 % of all branches (44 % of needle samples and 82 % of wood samples). The presence of S. sapinea in the galleries and on the surface of the beetle indicates that I. acuminatus may transport the pathogen and later introduce it into healthy trees. The bark beetle can transfer pathogenic fungus during maturation feeding on the shoots of healthy pine crowns and into the branches during making galleries.

Isolation of Fomitopsis pinicola from in-flight bark beetles (Coleoptera: Scolytidae)

Isolations of Hymenomycetes on a preferential medium were attempted from preflight pine engraver beetles, Ips pini, and the following in-flight bark beetles: pine engraver beetle, I. pini; western pine beetle, Dendroctonus brevicomis; mountain pine beetle, Dendroctonus ponderosae; and red turpentine beetle, Dendroctonus valens. Thirty pine engraver beetles removed from ponderosa pine slash (preflight) yielded no hymenomycete. However, Hymenomycetes were isolated from 50 of 114 beetles (all species) trapped in flight; Fomitopsis pinicola from 44, and other unidentified suspected Hymenomycetes, from 6. Cryptoporus volvatus was not isolated from any of the in-flight beetles. Since most of these isolates were without clamps (monokaryotic), the beetles may acquire basidiospores after emergence from beetle galleries in coniferous trees as hypothesized previously for the Douglas-fir beetle, Dendroctonus pseudotsugae. The isolation of F. pinicola from all species of in-flight bark beetles indicates that these beetles may be important in the dissemination of this hymenomycete.