Tree response and mountain pine beetle attack preference, reproduction and emergence timing in mixed whitebark and lodgepole pine stands (original) (raw)
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Plant, cell & environment, 2017
Warming climate is allowing tree-killing bark beetles to expand their ranges and access naïve and semi-naïve conifers. Conifers respond to attack using complex mixtures of chemical defenses that can impede beetle success, but beetles exploit some compounds for host location and communication. Outcomes of changing relationships will depend on concentrations and compositions of multiple host compounds, which are largely unknown. We analyzed constitutive and induced chemistries of Dendroctonus ponderosae's primary historical host, Pinus contorta, and P. albicaulis, a high-elevation species whose encounters with this beetle are transitioning from intermittent to continuous. We quantified multiple classes of terpenes, phenolics, carbohydrates, and minerals. Pinus contorta had higher constitutive allocation to, and generally stronger inducibility of, compounds that resist these beetle-fungal complexes. Pinus albicaulis contained higher proportions of specific monoterpenes that enhance...
Forest Ecology and Management, 2019
Introductions of alien forest insects can exert substantial ecological and economic impacts on natural forest systems. The mountain pine beetle, Dendroctonus ponderosae Hopkins, an aggressive bark beetle native to western North America, kills mature pines at outbreak levels and is currently expanding its geographic, altitudinal and host ranges across the continent. Its oligophagous feeding behavior and its ability to kill novel hosts in newly invaded areas of Alberta, Canada suggest that this insect could threaten pine forests in other regions of the world. Little is known of the susceptibility of Scots pine, Pinus sylvestris L., to mountain pine beetle. Scots pine is a potential novel host common to forests across Eurasia and introduced to North America. Laboratory studies indicate the insects can colonize and reproduce in harvested logs of the host. We measured outcomes of an outbreak by mountain pine beetle in mixed stands of mature Scots pine and ponderosa pine, P. ponderosa Dougl. ex. Laws. var. scopulorum Engelm., a historical host for the insect, in the Black Hills of South Dakota, U.S.A. We conducted a retrospective assessment of beetle attack and tree mortality of 165 trees (54 Scots pine and 111 ponderosa pine) of similar size and proximity that experienced high beetle pressure for three to four years ending in 2015. Our results show that mountain pine beetle can detect and attack live trees of Scots pine. Notably, we found that nearly 90% of Scots pines showed signs of attack, while no evidence of attack was found on the historical host in mixed stands. However, we found that Scots pines received half the attack density and demonstrated fifteen fold less likelihood of mortality in one year's time relative to ponderosa pine in nearby stands. These results are important for assessing the potential for mountain pine beetle to kill trees in Eurasia and North America in Scots pine stands.
Canadian Journal of Forest Research, 2015
Mountain pine beetle (Dendroctonus ponderosae Hopkins; Coleoptera: Curculionidae, Scolytinae) has killed millions of hectares of lodgepole pine (Pinus contorta Douglas ex Loudon) forest in western Canada, where it has recently established in the novel host jack pine (Pinus banksiana Lamb.) and threatens naïve red pine (Pinus resinosa Aiton) forests as the current outbreak expands eastward. It is therefore crucial to understand whether red pine is a suitable host for D. ponderosae. Host suitability was assessed by comparing the ability of beetles to produce pheromones and complete their development in red pine bolts inoculated with mating beetle pairs. We detected two of four primary pheromones, including trans-verbenol and verbenone, but not exo-brevicomin or frontalin. Beetle brood successfully developed in bolts, with reproductive parameters (e.g., female and larval galleries, pupal chamber, and number of broods emerged per mated pair of adults) that were similar to those reported...
2008
Dendroctonus adjunctus is an aggressive bark beetle species that attacks several species of pine throughout its range from southern Utah and Colorado south to Guatemala. A current outbreak of D. adjunctus provided a unique opportunity to study the relationship between this beetle and pine resin chemistry in northern Arizona. We compared the resin composition of trees that had been attacked by D. adjunctus compared with unattacked trees and found significant differences in the composition of the monoterpenes α-pinene, ß-pinene, myrcene and limonene between attacked and unattacked trees. Attacked trees contained significantly higher percentages of α-pinene, myrcene, and limonene, but lower levels of ß-pinene when compared to unattacked trees. Although it is unknown whether D. adjunctus prefers or is repelled by trees with specific monoterpene content, our results suggest that D. adjunctus may use specific chemical cues in host tree selection.
PeerJ, 2014
The mountain pine beetle, Dendroctonus ponderosae, is a significant pest of lodgepole pine in British Columbia (BC), where it has recently reached an unprecedented outbreak level. Although it is native to western North America, the beetle can now be viewed as a native invasive because for the first time in recorded history it has begun to reproduce in native jack pine stands within the North American boreal forest. The ability of jack pine trees to defend themselves against mass attack and their suitability for brood success will play a major role in the success of this insect in a putatively new geographic range and host. Lodgepole and jack pine were sampled along a transect extending from the beetle's historic range (central BC) to the newly invaded area east of the Rocky Mountains in north-central Alberta (AB) in Canada for constitutive phloem resin terpene levels. In addition, two populations of lodgepole pine (BC) and one population of jack pine (AB) were sampled for levels of induced phloem terpenes. Phloem resin terpenes were identified and quantified using gas chromatography. Significant differences were found in constitutive levels of terpenes between the two species of pine. Constitutive α-pinene levels-a precursor in the biosynthesis of components of the aggregation and antiaggregation pheromones of mountain pine beetle-were significantly higher in jack pine. However, lower constitutive levels of compounds known to be toxic to bark beetles, e.g., 3-carene, in jack pine suggests that this species could be poorly defended. Differences in woundinginduced responses for phloem accumulation of five major terpenes were found between the two populations of lodgepole pine and between lodgepole and jack pine. The mountain pine beetle will face a different constitutive and induced phloem resin terpene environment when locating and colonizing jack pine in its new geographic range, and this may play a significant role in the ability of the insect to persist in this new host.
2015
The secondary compounds of pines (Pinus) can strongly affect the physiology, ecology and behaviour of bark beetles (Coleoptera: Curculionidae, Scolytinae) that feed on host subcortical tissues. Jack pine (Pinus banksiana) has a wide distribution range in North America and thus variations in its secondary compounds, particularly monoterpenes, could affect the host expansion of mountain pine beetle (Dendroctonus ponderosae), which has recently attacked jack pine as a novel host and expanded its range into the boreal forest. I analyzed variations in monoterpene composition of jack pine foliage and phloem from natural and provenance stands representing populations from Alberta to the Atlantic coast. Additionally, the effects of variations in phloem monoterpene composition on pheromone production by mountain pine beetle were analyzed. Throughout its range, jack pine foliage monoterpenes were classified into three chemotypes characterized by high proportions of the monoterpenes α-pinene, β-pinene, or limonene. Expression of these chemotypes was controlled by both genetic and environmental factors and individual monoterpenes were correlated with climatic variables differently. Conversely, phloem monoterpenes were classified into groups characterized by high amounts of the monoterpenes (+)-α-pinene, 3-carene or no notably high individual compound and beetle aggregation and anti-aggregation pheromone production varied with these groups. Furthermore, pheromone production also varied between provinces, with the most aggregation pheromone produced in trees from Manitoba and Quebec. These results indicate that pheromone production by D. ponderosae will vary with host chemistry but remain a viable and important aspect of its survival and persistence in the boreal forest. iii Preface This document presents two studies (Chapters 2 and 3) intended for publication and represent collaborative work led by Dr Nadir Erbilgin of the University of Alberta. I was responsible for data collection and analyses, literature review and manuscript composition and writing throughout this document. Dr Erbigin was involved with concept formation and manuscript composition throughout the work. Additionally, Ahmed Najar of the University of Alberta was responsible for developing chemical analyses described in Chapters 2 and 3. For Chapter 2, Drs Jean Bousquet and Julie Godbout of Université Laval carried out field work and provided samples and manuscript edits. All research presented in this thesis was conducted in accordance with all applicable laws and rules set forth by provincial and federal governments and the U of A and all necessary permits were in hand when the research was conducted.
Ponderosa pine characteristics associated with attack by the roundheaded pine beetle
2010
The roundheaded pine beetle (Dendroctonus adjunctus Blandford [Coleoptera: Curculionidae, Scolytinae]) is an aggressive (tree-killing) bark beetle species that attacks several species of pine. Characteristics of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) trees chosen for attack by this beetle were studied in a current outbreak in northern Arizona. We found significant differences in basal area increment, crown width, lengths of internodes, subbranches, and needles, phloem thickness, and resin composition between attacked and unattacked trees. Attacked trees had significantly lower basal area increment and internode and needle lengths but longer subbranch lengths at the top of the crown and longer crown widths. Attacked trees also had thicker phloem and contained a significantly higher percentage of ␣-pinene in resin, but a lower percentage of longifolene than unattacked trees. A baited tree experiment showed that attacks by the roundheaded pine beetle did not affect resin composition through time. Overall, our results suggest that host selection by the roundheaded pine beetle may not be random and that tree growth characteristics and resin composition are probably important factors in host selection. FOR. SCI. 56(5):473-483.
Forest Ecology and Management, 2008
Mountain pine beetle, Dendroctonus ponderosae Hopkins can cause extensive tree mortality in ponderosa pine, Pinus ponderosa Dougl. ex Laws., forests in the Black Hills of South Dakota and Wyoming. Most studies that have examined stand susceptibility to mountain pine beetle have been conducted in even-aged stands. Land managers increasingly practice uneven-aged management. We established 84 clusters of four plots, one where bark beetle-caused mortality was present and three uninfested plots. For all plot trees we recorded species, tree diameter, and crown position and for ponderosa pine whether they were killed or infested by mountain pine beetle. Elevation, slope, and aspect were also recorded. We used classification trees to model the likelihood of bark beetle attack based on plot and site variables. The probability of individual tree attack within the infested plots was estimated using logistic regression. Basal area of ponderosa pine in trees !25.4 cm in diameter at breast height (dbh) and ponderosa pine stand density index were correlated with mountain pine beetle attack. Regression trees and linear regression indicated that the amount of observed tree mortality was associated with initial ponderosa pine basal area and ponderosa pine stand density index. Infested stands had higher total and ponderosa pine basal area, total and ponderosa pine stand density index, and ponderosa pine basal area in trees !25.4 cm dbh. The probability of individual tree attack within infested plots was positively correlated with tree diameter with ponderosa pine stand density index modifying the relationship. A tree of a given size was more likely to be attacked in a denser stand. We conclude that stands with higher ponderosa pine basal area in trees >25.4 cm and ponderosa pine stand density index are correlated with an increased likelihood of mountain pine beetle bark beetle attack. Information form this study will help forest managers in the identification of uneven-aged stands with a higher likelihood of bark beetle attack and expected levels of tree mortality.
Forests, 2018
Research Highlights: The biology of mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins, in Colorado’s lodgepole pine forests exhibits similarities and differences to other parts of its range. Brood emergence was not influenced by stand density nor related to tree diameter. The probability of individual tree attack is influenced by stocking and tree size. Findings have implications for understanding MPB as a disturbance agent and for developing management strategies. Background and Objectives: MPB causes extensive tree mortality of lodgepole pine, Pinus contorta Douglas ex Loudon, across the western US and Canada and is probably the most studied bark beetle in North America. However, most of the current knowledge on the biology and ecology of MPB in lodgepole pine comes from the Intermountain Region of the US and western Canada. Little information is available from Colorado. This is the first study addressing effects of stand stocking levels on the biology of MPB and quantif...