Verbenone protects pine trees from colonization by the six-toothed pine bark beetle, Ips sexdentatus Boern. (Col.: Scolytinae)

Abstract

Verbenone and trans‐conophthorin were tested against the aggregation pheromone of the six‐toothed bark beetle (Ips sexdentatus Boern.) on two trapping bioassays. Two different release rates of verbenone (2 mg/24 h and 40 mg/24 h) gave similar significant catch reductions (by 73% and 82%, respectively), whereas trans‐conophthorin lowered the catch by 45%. Joint release of both compounds reduced trap catches by 90%. Furthermore, the effect of these semiochemicals on Thanasimus formicarius L. and Temnoscheila coerulea Olivier, two important natural enemies of I. sexdentatus, as well as Hylurgus ligniperda Fabricius, a native associated scolytid, was evaluated. Both predators were significantly affected by verbenone, whereas the effect on H. ligniperda could not be concluded. Based on these results, verbenone was used in a third experiment to protect standing healthy Pinus nigra salzmannii J. F. Arnold trees from induced I. sexdentatus attack. The experiment consisted of two treatments and 20 paired‐tree replicates. Treatments were pheromone‐baited control trees and baited trees treated with verbenone (60 mg/24 h). These trees served as centres of 10 m radius plots from where a number of plot variables was recorded for local stand description. After the experimental period, all control trees had suffered attacks by I. sexdentatus, whereas trees treated with verbenone were significantly less attacked. Among other stand variables considered in the study, the following characterized the variation among plots most efficiently: (i) plot density, (ii) dominant height and (iii) the proportion of suppressed or (iv) intermediate dominance level trees in the plot. However, these variables did not significantly affect the repellent effect by verbenone. Further research should evaluate the use of verbenone on management strategies of ongoing attacks of I. sexdentatus.

Field response of the six‐toothed pine bark beetle, Ips sexdentatus (Col.: Curculionidae, Scolytinae), to pheromonal blend candidates

“…2007), as inhibition of I. sexdentatus response has been reported for known repellents, such as verbenone or non‐host volatiles (Jactel et al. 2001; Etxebeste and Pajares 2011). Future work should focus on refining the aggregation blend by determining pheromone compound ratios and optical isomers and testing and incorporating host signals to further increase the effectiveness of the lure, not just by total numbers, but also by reducing captured non‐targeted species.…”

“…Our results are inconclusive, as no differences were found in bioassays 3 or 4, except for myrtenol alone which caught almost no beetles (table 3). As for H. ligniperda Fabricius, this secondary beetle is generally attracted to host semiochemicals but has also been shown to be attracted to those of bark beetles (Reay and Walsh 2002; Etxebeste and Pajares 2011).…”

Southern Pine Beetle, Dendroctonus frontalis, Antennal and Behavioral Responses to Nonhost Leaf and Bark Volatiles

“…Verbenone is hypothesized to function for D. frontalis and many other bark beetle systems as both an antiaggregation pheromone that signals complete colonization of the host bole, and as a microbe-generated indicator of host decay and unsuitability (Byers, 1989;Lindgren and Miller, 2002;Sullivan, 2011). In trapping and tree protection studies, verbenone significantly enhances the capacity of nonhost volatiles to inhibit attraction and attacks by Dendroctonus Fettig et al, 2009) and Ips (Zhang, 2003;Zhang and Schlyter, 2003;Graves et al, 2008;Etxebeste and Pajares, 2011), and it may prove so for D. frontalis also.…”

“…), and has been shown to elicit antennal responses and/or inhibit semiochemical attraction in numerous scolytid species: Dendroctonus brevicomis LeConte (Shepherd et al, 2007), D. ponderosae Hopkins (Huber et al, 1999), D. pseudotsugae Hopkins (Huber et al, 1999(Huber et al, , 2000a, Dryocoetes confusus Swaine (Huber et al, 2000a), Ips perturbatus (Eichhoff) (Graves et al, 2008), I. pini (Say) (Huber et al, 2000a, I. sexdentatus Boern. (Jactel et al, 2001;Etxebeste and Pajares, 2011), I. typographus (L.) (Zhang, 2003;Zhang and Schlyter, 2003), and Trypodendron lineatum (Olivier) . Strong antennal sensitivity to transconophthorin suggests the possibility that behavioral activity also exists with D. frontalis.…”

Bark Beetles Control in Forests of Northern Spain

“…In contrast with these results, bark beetle species (Tomicus piniperda, Orthotomicus erosus, Dryocoetes autographus, Hypothenemus eruditus, Xyleborus dryographus, Hylastes ater, H. attenuatus and Hylurgus ligniperda), trapped accidentally while carrying out that bioassay, have been shown to be not affected significantly by verbenone. Moreover, Etxebeste and Pajares (2011) tested verbenone and trans-conophthorin against I. sexdentatus populations present in mixed pine stands (P. sylvestris, P. nigra and P. pinaster). Two verbenone release rate (2, 40 and 60 mg/day) and one trans-conophthorin release rate (0.3 mg/day) were tested in two different field trapping bioassays with Ipsdienol 2.35 mg/day as attractant.…”