Bark

About: Bark is a research topic. Over the lifetime, 12004 publications have been published within this topic receiving 147931 citations.

Fungal Associates of European Bark Beetles With Special Emphasis on the Ophiostomatoid Fungi

Abstract: Fungi are common and well-known associates of bark beetles (Coleoptera: Scolytidae). The relationship between fungi and scolytids was recognized relatively long ago. Schmidberger (1836) described an “ambrosia” in the galleries of the wood-inhabiting bark beetle Xyleborus dispar, and Hartig (1844) discovered the fungal nature of this “ambrosia” lining the tunnels of the insects. Likewise, Hartig (1878) first recognized the interrelationships between insect damage, discoloration of wood and fungi, and during his studies on blue-stain in the sapwood of conifers, Munch (1907, 1908) observed that blue-stain in living trees and lumber is associated with attack by bark beetles. Since these early discoveries a large number of investigations on various aspects of the association of fungi with bark beetles have been carried out. Scolytids are among the most economically important pests of the world s forests, especially conifer forests in the boreal and temperate regions of the Northern hemisphere (Postner 1974; Schwerdtfeger 1981; Wood 1982; Wood and Bright 1992). A considerable number of fungal associates of bark beetles are known as forest pathogens in their own right, causing vascular wilt or vascular stain diseases (Webber and Gibbs 1989; Harrington 1993a, 1993b; Wingfield et al. 1993). Many other species give rise to discoloration in the sapwood of conifers and cause enormous losses to forestry and wood industry worldwide (Whitney 1982; Seifert 1993; Butin 1996). Although the association between scolytids and fungi has been recognised for more than one century, many fundamental aspects of this relationship are still poorly

Interaction of pre-attack and induced monoterpene concentrations in host conifer defense against bark beetle-fungal complexes.

Abstract: Two pine species (Pinus resinosa, P. banksiana) responded to inoculation with fungi carried by bark beetles by rapidly increasing monoterpene concentrations at the entry site. Changes in total monoterpenes were more pronounced than changes in proportionate compositions. The extent and rate of host response was affected by fungal species, the viability of the inoculum, and host tree species. In general, host responses were highest to fungi that are phytopathogenic and consistently associated with the major bark beetles in the study region. Simple mechanical wounding cannot account for the observed allelochemical changes, as aseptic inoculations elicited only minor reactions. Similarly, inoculation with autoclaved inviable fungi generally elicited intermediate responses, suggesting that both structural and metabolic fungal properties are important. Responses by jack pine, P. banksiana, were generally more rapid and variable than those of red pine, P. resinosa. Dose-toxicity experiments with synthetic compounds demonstrated that monoterpene concentrations present in vivo only a few days after simulated attack are lethal to most beetles. Constitutive (pre-attack) monoterpene levels can also exert some toxicity. Because bark beetles engage in pheromone-mediated mass attacks that can deplete host defenses, constitutive monoterpene levels, while a necessary early phase of successful plant defense, appear insufficient by themselves. Such interactions between constitutive and induced defense chemistry may be important considerations when evaluating general theories of plant defense.