Pinyon Engraver Beetle Acoustics: Stridulation Apparatus, Sound Production and Behavioral Response to Vibroacoustic Treatments in Logs

Bark beetles are among the most influential biotic agents in conifer forests, and forest management often focuses on bark beetle chemical communication for tree protection. Although acoustic communication occurs in many bark beetle species, we have yet to utilize acoustic communication for bark beetle control. Here, we describe the stridulatory organs and ‘stress’ chirps of the pinyon engraver, Ips confusus, a significant pest and mortality agent of pinyon pine in western North America. Only females possessed stridulatory organs and their stress chirps varied significantly in duration, pulses per chirp, and dominant frequency. We tested an array of acoustic-vibrational treatments into logs but were unable to disrupt male entry into logs or alter female–male interactions, female tunneling, and female oviposition. We found acoustic–vibrational treatments had little effect on I. confusus behavior and suggest further studies if acoustic methods are to be utilized for bark beetle control.

Impacts of black stain root disease in recently formed mortality centers in the piñon-juniper woodlands of southwestern Colorado

Thirty discrete black stain root disease (BSRD) mortality centers, caused by Leptographium wageneri (Kendr.) Wingf. var. wageneri, were examined in 1999 to determine the effects of BSRD on the composition and structure of piñon–juniper woodlands at the tree, shrub, and herbaceous plant levels and on tree-seedling regeneration. In these recently formed mortality centers, the majority (68%) of all piñon (Pinus edulis Engelm.) was dead, 76% of piñon were affected by BSRD, and 70% had evidence of piñon ips bark beetle (Ips confusus Leconte) attack. BSRD mortality centers had a mean area of 0.28 ha (range 0.07 to 0.63 ha). There were no statistically significant (p > 0.05) differences in shrub composition, cover, or diversity between mortality centers and the unaffected surrounding woodlands. Herbaceous plant cover was significantly greater (p < 0.001) within mortality centers and frequency responses were species specific. There were no significant (p = 0.629) differences in the density of piñon regeneration inside mortality centers compared with outside mortality centers. The pathogen was regularly isolated from piñon roots dead for 5–8 years and once from a root dead for 16 years. The rate of radial expansion of mortality centers averaged 1.1 m/year (0.07 SE). The rate of mortality center expansion was not significantly (p > 0.05) related to available water-holding capacity, percent organic matter, pH of soils, piñon density, or any other site data recorded.

Fine structure of degenerating and regenerating flight muscles in a bark beetle, Ips confusus. II. Regeneration

The flight muscles of the bark beetle Ips confusus regenerate by two means, by formation and differentiation of new myoblasts, and by the regeneration of the old flight muscle itself. Mononucleated myoblasts appear in beetles which have been in the inner bark of ponderosa pine logs for 5 days. These cells apparently fuse with other myoblasts to form multinucleated cells. By the end of the ninth day of regeneration the myofilaments become attached to an incoherent Z line. By the 11th day of regeneration these differentiating myoblasts appear very much like the fibers of the regenerating old flight muscle.Simultaneously the fibers of the old degenerate muscles show signs of regeneration. On the sixth day after the beetles entered the bark, rearrangement of the existing degenerate myofilaments takes place. The incoherent and diffused Z line shows some degree of reorganization. Numerous ribosomes are present between the filaments. Between the 7th to 11th days of regeneration the mitochondria appear to fuse to form giant mitochondria up to five sarcomeres in length. These mitochondria by subsequent divisions give rise to numerous mitochondria. Almost invariably the line of mitochondrial fission is aligned with the Z line. The presence of numerous ribosomes and polysomes in the fibers indicate a high protein synthetic activity. By the end of the 13th day regeneration of the flight muscle appears complete and the beetles are now ready to reemerge. These results further confirm our earlier observation (Bhakthan et al. 1970) that flight muscle degeneration in I. confusus is a reversible process.