Ecological Interactions of Bark Beetles with Host Trees

Certain species of bark beetles in the insect order Coleoptera, family Curculionidae (formerly Scolytidae), are keystone species in forest ecosystems. However, the tree-killing and wood-boring bark and ambrosia beetles are also among the most damaging insects of forest products including lumber, paper, and ornamental/recreational trees. The pest status of these beetles has been elevated with the advance of global warming and moderate to severe area-wide droughts, exacerbated by mismanagement and prevention of fires over decades. The ecology and chemical ecology of bark beetles has been and still is an exciting area of research, particularly since bark beetles utilize a wide array of semiochemicals in communication and in interactions with plants. Bark beetle chemical ecology is intimately connected and intertwined with behavioral and physiological processes that are still largely unknown in many species. Development of more efficient pest management practices will require a much deeper understanding of the ecology of bark beetles facilitated by interdisciplinary observations and experiments on many levels. Potential topics for this special issue include host-tree finding and selection, resistance by the tree, avoidance of tree defenses, insect/tree microbial associations, regulation of colonization density, ecology of predators and parasitoids, communication, biosynthesis of semiochemicals, behavioral assays and antennal responses, population management, models of dispersal and trapping, and reviews. Many of these topics and others are covered in part in the 12 articles in the special issue on " Bark beetle ecology and interactions with host trees. " F. Schlyter in his article " Semiochemical diversity in practise: Antiattractant semiochemicals reduce bark beetle attacks on standing trees—a first meta-analysis " brings together the results of 33 recent studies on attractive traps and repellent chemicals (verbenone and/or nonhost tree volatiles) designed to reduce bark beetle colonization of host trees. He found using Cohen's effect size that the use of repellent chemicals caused a significant reduction in attacked and killed trees in most studies. The results were not affected by publication year and the plots indicated there were little bias in reporting of only those studies showing effects of repellents. The use of natural repellents at higher dosages can allow stressed trees to survive by protecting themselves with their innate defenses. He recommends more precise reporting of results, more unified experimental designs, and further meta-analyses that include " grey literature " and more beetle species. S. D. Reay et al. in their article " Hylastes ater (Curculion-idae: Scolytinae) affecting Pinus radiata seedling …