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   Dendroctonus valens (insect)
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    Details of this species in Arizona
    Status: Native
    Invasiveness: Uncertain
    Occurrence: Established
    Source: Williams et al. 2008
    Arrival Date:
    Species Notes for this Location:
    Management Notes for this Location:
    Williams and colleagues (2008) investigated abundance and flight periodicity of bark beetles, including Dendroctonus valens, among three different elevation bands of ponderosa pine (Pinus ponderosa) forest in north-central Arizona (USA) for three years using pheromone-baited Lindgren funnel traps. Elevation bands were: 1600 to 1736 meters, 2058 to 2230 meters and 2505 to 2651 meters. D. valens was found at all three elevations, however, a greater abundance of D. valens was observed at the high elevation zone (2505 to 2651 meters), which is higher than the favored elevation interval (2100 to 2500 meters) for D. valens in Mexico (Salinas-Moreno et al. 2004, in Williams et al. 2008). At all elevations D. valens flight activity occurred from early April to late October with peak flight activity in May and with activity tapering off by August. This period of flight activity is similar to the reported flight period in its northern range (Wood 1982 in Williams et al. 2008). D. valens has one generation in two years in the coldest parts of its range, but may have two to three generations per year in warmer climates (Smith 1971 Williams et al. 2008).

    The importance of synchronised bark beetle attacks is poorly understood. In southwest North America ponderosa pine forests D. adjunctus and D. valens often occur from the base of the tree to half a meter in height. Beetle success in killing a vigorous host by a synchronised attack could offset costs of inter-specific competition. Alternatively, niche overlap of two or more species may prevent an individual species from ever dominating utilisation of the resource and reaching outbreak levels. Inter-specific competition for resources may hold invasive species in check in their native range. This lack of inter-specific competition in introduced areas may explain the severity of outbreak of D. valens in northern Chinese forests. Sakai and colleagues (2001, in Erbilgin et al. 2007) reported that the reasons underlying the greater tree mortality in China could include a lack of evolutionary adaptation to this new insect-host (Dendroctonus valens-Pinus tabulaeformis) association.

    Wallin and colleagues (2008) found that the thinning of ponderosa pine Pinus ponderosa near Flagstaff (Arizona, USA) decreased the percentage of trees with bark beetle infestations. Beetle attacks were induced by beetle community response to a Dendroctonus brevicomis pheromone; the D. brevicomis pheromone attracts several bark beetle species. The positive affect of restoration treatments on tree resistance may be due to the underlying stimulation of resin defenses. Thinning treatments have been reported to increase production of carbon-based defenses such as resin in some studies (Kolb et al. 1998, Feeney et al. 1998, McDowell et al. 2007, in Wallin et al. 2008). These findings along with those of the authors suggest that thinning reduces resource competition among trees and hence, tree stress, and increases carbon allocation to resin defenses in the tree. Resin flow after phloem wounding was greater in restoration treatments than in control in the first and second year after treatment. The authors found a negative correlation between resin volume and the number of D. valens brood which emerged from the bole.

    Location Notes:
    Last Modified: 16/02/2009 3:34:24 p.m.

ISSG Landcare Research NBII IUCN University of Auckland