The complex symbiotic relationships of bark beetles with microorganisms: a potential practical approach for biological control in forestry

Abstract

Bark beetles, especially Dendroctonus species, are considered to be serious pests of the coniferous forests in North America. Bark beetle forest pests undergo population eruptions, causing region wide economic losses. In order to save forests, finding new and innovative environmentally friendly approaches in wood-boring insect pest management is more important than ever. Several biological control methods have been attempted over time to limit the damage and spreading of bark beetle epidemics. The use of entomopathogenic microorganisms against bark beetle populations is an attractive alternative tool for many biological control programmes in forestry. However, the effectiveness of these biological control agents is strongly affected by environmental factors, as well as by the susceptibility of the insect host. Bark beetle susceptibility to entomopathogens varies greatly between species. According to recent literature, bark beetles are engaged in symbiotic relationships with fungi and bacteria. These types of relationship are very complex and apparently involved in bark beetle defensive mechanisms against pathogens. The latest scientific discoveries in multipartite symbiosis have unravelled unexpected opportunities in bark beetle pest management, which are discussed in this article.

Characterization of the Bacterial Community Associated with Larvae and Adults ofAnoplophora chinensisCollected in Italy by Culture and Culture-Independent Methods

“…In addition to the bacterial lignocellulose-degrading activities, the nutrient-extracting capacities exerted by fungi strictly associated with the host are thought to contribute to host nutrition, as recently indicated by enzymatic proprieties of the A. glabripennis isolate F. solani [47]. Moreover, some of these bacteria with specific enzymatic degrading activities are thought to play important roles in the detoxification of plant compounds, production of metabolites against pathogens, and plant-insect interactions [46, 48]. For example, several bacterial genera affiliated to Actinobacteria, Gammaproteobacteria, Betaproteobacteria, and Firmicutes that are contained in the oral secretions of the bark beetle Dendroctonus rufipennis were demonstrated to significantly inhibit the growth of antagonistic fungi [49].…”

Population Structure of Mountain Pine Beetle Symbiont Leptographium longiclavatum and the Implication on the Multipartite Beetle-Fungi Relationships

“…The bark beetle-microbe system represents a complex community of symbionts, which provides an opportunity to study the impact of multipartite symbiont associations on population structure, ecosystem health, and pest management [11], [12], [13]. Representatives of Dendroctonus are serious forest pests in North America.…”

Virulence and horizontal transmission of Beauveria pseudobassiana S.A. Rehner & Humber in Ips sexdentatus and Ips typographus (Coleoptera: Curculionidae)

“…They are thus still serious pests of coniferous forests in Turkey and other countries (Dubbel et al, 1993;Popa et al, 2011). Therefore, there is a need to find new control methods against these pests.…”

“…To date, some strategies have been used to control these pests, such as removing and debarking of infested trees, trap trees, insecticide treatments, phytosanitary measures, and pheromone trapping (Dubbel, 1993;Popa et al, 2011). In addition, several biological control agents, such as Thanasimus formicarius (Linnaeus) (Coleoptera: Cleridae) and Rhizophagus dispar (Paykull) (Coleoptera: Rhizophagidae), which are predators of these beetles, have been considered to prevent their damage and control the spread of Ips species (Yüksel, 1998).…”