Bark beetle feeding

Bark beetle-host tree associations are ancient, which may explain why different beetle species prefer or are even restricted to certain hosts (rev. ). Beetles seem to be able to tolerate the resin components of host trees, but not those from non-host trees, suggesting that detoxification mechanisms for different beetle species are tuned to their host trees. Indeed, it has been hypothesized that bark beetle feeding may contribute to compositional variation of resin within different pine... 

Pinocembrin (50) has been implicated as an attractant to a bark beetles feeding on fruit trees (Harbome, 1991). In contrast, the flavonoid aglycone, morin (39) [as well as iso-quercitrin (51) and several essential oils], is involved in feeding of silkworm larvae Bombyx mod) on mulberry plants Morus nigra) (Harbome, 1991). 

Often related insect species are not all sensitive to a particular allomone. For example, juglone is a feeding deterrent to the smaller European elm bark beetle (Scolytus multistriatus) but not to the closely related hickory bark beetle (Scolytus quadrispinosus) (106,107). 

For some herbivores, the responses to herbivore-induced plant odors differ under different circumstances. For instance, the spider mite I urticae is more attracted to healthy lima bean leaves than leaves that emit volatiles induced by spider mite infestation (Dicke, 1986 Dicke and Dijkman, 1992). However, Pallini etal. (1997) found that the same mite is attracted to cucumber plants that are already infested by conspecifics. In contrast, T urticae avoids the odor of cucumber plants under attack by the western flower thrips, FranJdiniella occidentalis, which is a herbivore but also feeds on spider mites. Bark beetles can cause strong reactions in their host trees, resulting in the emission of a blend of volatile terpenoids that, in combination with aggregation pheromenes, is used in mass attacks. These same substances may attract predators (Byers, 1989) and parasitoids (Sullivan et al, 2000 Pettersson, 2001 Pettersson et al, 2001) to infested trees. 

Magnoline Inhibited feeding of bark beetle (Scolytus multistriatus) 439... 

Byers J. A. (1981) Pheromone biosynthesis in the bark beetle, Ips paraconfusus, during feeding or exposure to vapours of host plant precursors. Insect Biochem. 11, 563-569. 

Figure 6.13 Examples of the application of normal-phase, radio-HPLC to the analysis of de novo biosynthetic pathways in bark beetles (Scolytidae). Demonstration of sex-specific de novo biosynthesis of ipsenol, ipsdienol, and amitinol through radio-HPLC analysis of pentane extracts of Porapak-trapped volatiles from (A) male and (B) female Ips paraconfusus Lanier feeding for 168 h in Pinus ponderosa and (C) male and (D) female Ips pini (Say) feeding for 168 h in Pinus jeffreyi (Seybold et al., 1995b). Demonstration of sex-specific de novo biosynthesis of frontalin through radio-HPLC analysis of pentane extracts of Porapak-trapped volatiles from (E) male and (F) female...

JH III is sufficient to induce pheromone biosynthesis in starved I. pini and D. jeffreyi, suggesting a relatively simple endocrine regulation. However, starved I. paraconfusus cannot be induced to synthesize pheromone by JH III, despite the fact that HMG-R expression rises with JH III treatment. Pheromone biosynthesis in I. paraconfusus requires feeding (Seybold et al., 2000 Tillman et al., in preparation). Since HMG-R expression is apparently regulated similarly in both species, I. paraconfusus must require an additional signal in order to activate pheromone biosynthesis. The necessary factors are likely to act post-transcriptionally or post-translationally on HMG-R. These studies show that extending information from one species to another must be done with caution, as even closely related bark beetles seem to have very different regulatory schema. 

Naturally occurring variations in HMG-R mRNA levels due to feeding or development remain unknown. Fed bark beetles are refractory to numerous RNA isolation protocols (Tillman and Tittiger, unpublished results), making these... 

Elm bark beetle boring and feeding deterrents from Phomopsis oblonga, N. 

Bark beetle reproduction requires a pioneer beetle (male or female, depending on the species) to initiate feeding on a host pine tree. The tree is protected by the production of constitutive and induced resin components that serve as physical and toxic barriers to colonization. In order to successfully overcome these defenses, bark beetles rely on a mass attack strategy whereby hundreds to thousands of conspecifics aggregate at the same tree. This is coordinated by the production of volatile aggregation pheromone components by the pioneer beetles. 

AYRES, M.P., WILKENS, R.T., RUEL, J.J., LOMBARDERO, M.J., VALLERY, E., Nitrogen budgets of phloem-feeding bark beetles with and without symbiotic fungi. Ecology, 2000, 81, 2198-2210. 

ELKINTON, J.S., WOOD, D.L., Feeding and boring behavior of the bark beetle Ips paraconfusus (Coleoptera Scolytidae) on the bark of a host and non-host tree species. Can. Entomol, 1980, 112, 797-809. 

---