The introduced bark beetles Hylurgus ligniperda and Hylastes ater (Coleoptera: Scolytidae) in Chile: seasonal flight and effect of Pinus radiata log placement on colonization

Abstract

The seasonal flight of Hylurgus ligniperda (Fabr.) and Hylastes ater (Paykull) and the effect of log placement in Pinus radiata D. Don plantations on colonization by these species in Chile are described. Seasonal flight activity was monitored with α-pinene and ethanol-baited traps at three sites and colonization synchrony with trap logs. In two experiments with individual logs and log decks, data were recorded on adults found under the logs, attacks on the bark surface, and adults beneath the bark of logs in three storage treatments: individual logs and log decks (1) touching the soil; (2) elevated above the soil; and (3) touching other logs (individual logs) or logs separated with spacers (log decks). Each treatment was replicated in a plantation and a clearcut. At San José (region IX) and Peña Blanca (region VIII), H. ligniperda flew primarily in spring and H. ater flew in spring and fall. At Brasil (region VIII), H. ligniperda and H. ater flew primarily in summer through fall. The flight of H. ligniperda was more synchronized with colonization of logs than was that of H. ater. The mean number of attacks was significantly higher on individual logs and log decks stored on the soil than on those elevated above the soil, and significantly higher in the clearcut than in the plantation. Mean numbers of adults beneath the bark did not vary significantly among individual-log treatments, but were significantly lower in the log decks separated by spacers. Logging during nondispersal periods (June–August in regions VIII–X) and storing log decks above the soil could reduce beetle colonization of newly cut logs. With this information, management of recently cut logs (harvesting, transport, and storage operations) could be scheduled and executed so as to reduce the risk of these species being introduced into log-importing countries.

Predicting sapstain and degrade in fallen trees following storm damage in a Pinus radiata forest

“…The billet logs demonstrated greater colonisation by H. ater and H. ligniperda where there was ground contact, which corroborates the results of an earlier study (Mausel et al, 2007). This provides an additional explanation for an initially low beetle colonisation rate on the fallen study trees, which were suspended above ground level for most of their stem length with a low incidence of contact.…”

“…Reay and Walsh, 2001; cf. similar findings with P. radiata in Chile, Mausel et al, 2007). Only H. ater was present in any numbers in traps and billets at the time of the storms, while other species remained largely inactive until October 2008.…”

Patterns in flight phenologies of bark beetles (Coleoptera: Scolytinae) in commercial pine tree plantations in Uruguay

“…There was no log colonization during summer, therefore, the small activity peaks of H. ligniperda during this season suggest new reproductive galleries with low or non-dispersion rates. Data from Chile suggest one or two activity peaks during the year, with no generation number associated (Mausel et al 2007). The authors suggest the overlap of generations with fertilized females ovipositing in the same host if it is still suitable for a new maternal gallery.…”

An Experimental Test of Insect-Mediated Colonisation of Damaged Pinus radiata Trees by Sapstain Fungi

“…This was mirrored almost exactly by the pattern of bark beetle colonisation, in this case by Hylastes ater and Hylurgus ligniperda . As these species are known to feed preferentially on roots, the lower stem and other parts of trees that are in ground contact, they are behaviourally adapted to preferentially colonise logs where they are in contact with the ground [34].…”

“…As H. ater and H. ligniperda are known to preferentially colonise logs that are in contact with the ground [34], the full length of every log was placed in ground contact. At each site, the 10 uncaged and 10 caged logs were placed at random points in a 4.5×6 m grid pattern, all with the long axis of the log facing north, separated by an equal distance of 1.5 m from any other log.…”