Bark beetles and the stain fungi they transport experience two very different environments when attacking living conifers. Early in the attack they are confronted with constitutive levels of defensive compounds, but trees rapidly accumulate much higher concentrations near the site of infection. The resin is composed of a diverse array of compounds, including monoterpenes, sesquiterpenes, diterpene acids and phenolics. Monoterpenes have been the most studied and have been shown to be attractive, repulsive, or toxic to beetles depending on concentration, and inhibitory to fungi. Little is known about the role the other resin components have on beetle and fungal performance. We studied one class of resin compounds, diterpene acids, to determine their impact in red pine (Pinus resinosa (Aitman))-pine engraver (Ips pini (Say))-stain fungi (Ophiostoma ips (Rumbold) Nannfeldt) interactions. Diterpene acids affected the host selection behavior of I. pini and the mycelial growth of O. ips in dose-dependent fashion. Activity varied among compounds. The overall role of diterpene acids in conifer defense against bark beetle – fungal complexes is considered by comparing results with monoterpenes.
Species 1: Coleoptera Scolytidae Ips pini (Pine engraver)
Species 2: Pinales Pinaceae Pinus resinosa (Red pine)
Species 3: Ascomycetes Ophiostomaceae Ophiostoma ips
Keywords: diterpene acids, stain fungi
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