Pine Bark Beetle Research Articles

The South Dakota Pine Bark Beetle Caper

The South Dakota Pine Bark Beetle Caper

Bark beetles attacking conifer seedlings: picking on the weakest or feasting upon the fittest?

Summary Plant stress from causes such as drought is thought to increase the susceptibility of plants to herbivore attack and damage. Although this forms the basis of the widely cited plant stress hypothesis, there are few cases where this has been tested thoroughly. We compared the frequency of attack and damage of an invasive pine bark beetle Hylates ater, on seedlings of Pinus radiata, using a 2 × 2 factorial design with artificially induced stress and insecticide application to distinguish effects of beetle attack and direct effects of stress. Contrary to expectations based on the plant stress hypothesis, twice as many unstressed seedlings (22%) were attacked than stressed seedlings (11%). However, stressed seedlings were twice as likely to experience sustained bark beetle feeding resulting in girdling, than unstressed seedlings (31% and 15%, respectively). In response to beetle attack, unstressed seedlings showed much stronger resin production than stressed seedlings, which is likely to explain the greater survival of unstressed seedlings after attack. Experimental drought stress caused a 50% reduction in shoot growth. Synthesis and applications. Maximizing seedling vigour and minimizing (pre‐)planting stress are key for the resilience of planted forests. Managers should emphasize a stress‐free transition of seedlings from nursery to field as well as correct planting techniques, in order to safeguard this vulnerable stage. This is particularly crucial since drought stress and insect invasions are likely to increase as a result of global change.

Enantiospecific responses of southern pine beetle (Dendroctonus frontalis) and its clerid predator, Thanasimus dubius, to α-pinene

Multi-trophic interactions between pine bark beetles, their host trees, and predators are mediated in part by volatile terpenes in host tree oleoresin that can influence aggregation and/or host finding by both prey and predator species. The southern pine beetle, Dendroctonus frontalis Zimmermann, mass-attacks pine trees in response to its aggregation pheromone combined with host resin odors including a-pinene. We investigated discrimination of a- pinene enantiomers in olfactory responses of D. frontalis, and in behavioral responses of D. frontalis and its major clerid predator, Thanasimus dubius (Fabricius). Trapping trials in the spring and fall assessed attraction of both species to the D. frontalis aggregation pheromone com- ponents, frontalin and endo-brevicomin, either alone or in combination with a-pinene lures of differing enantiomeric compositions. a-Pinene lures enriched with the (?)-enan- tiomer (97.5 %) increased D. frontalis catches significantly more than (-)-enriched (93 %) lures, but did not differ from racemic lures. Sexes of D. frontalis did not differ from one another in their responses to the enantiomers, and there was no difference in lure discrimination by D. fron- talis and T. dubius. Thanasimus dubius did not distinguish between different a-pinene enantiomers. Dose-response electroantennogram studies of D. frontalis indicated that their antennae had a slightly lower response threshold to (?) than (-)-a-pinene. Each enantiomer habituated the antennae more to itself than to its antipode, implying the existence of olfactory receptors with differing affinities for enantiomers. The preference of D. frontalis for (?)-a- pinene may affect its host selection behavior, and should be considered in population monitoring lures.

Impact of mountain pine beetle induced mortality on forest carbon and water fluxes

Quantifying impacts of ecological disturbance on ecosystem carbon and water fluxes will improve predictive understanding of biosphere—atmosphere feedbacks. Tree mortality caused by mountain pine bark beetles (Dendroctonus ponderosae) is hypothesized to decrease photosynthesis and water flux to the atmosphere while increasing respiration at a rate proportional to mortality. This work uses data from an eddy-covariance flux tower in a bark beetle infested lodgepole pine (Pinus contorta) forest to test ecosystem responses during the outbreak. Analyses were conducted on components of carbon (C) and water fluxes in response to disturbance and environmental factors (solar radiation, soil water content and vapor pressure deficit). Maximum CO2 uptake did not change as tree basal area mortality increased from 30 to 78% over three years of beetle disturbance. Growing season evapotranspiration varied among years while ecosystem water use efficiency (the ratio of net CO2 uptake to water vapor loss) did not change. Between 2009 and 2011, canopy water conductance increased from 98.6 to 151.7 mmol H2O m−2 s−1. Ecosystem light use efficiency of photosynthesis increased, with quantum yield increasing by 16% during the outbreak as light increased below the mature tree canopy and illuminated remaining vegetation more. Overall net ecosystem productivity was correlated with water flux and hence water availability. Average weekly ecosystem respiration, derived from light response curves and standard Ameriflux protocols for CO2 flux partitioning into respiration and gross ecosystem productivity, did not change as mortality increased. Separate effects of increased respiration and photosynthesis efficiency largely canceled one another out, presumably due to increased diffuse light in the canopy and soil organic matter decomposition resulting in no change in net CO2 exchange. These results agree with an emerging consensus in the literature demonstrating CO2 and H2O dynamics following large scale disturbance events are dependent not only on tree mortality but also on the remaining and new vegetation responses because mortality and recovery occur at the same time.

Relative methyl bromide tolerances of <i>Arhopalus ferus</i> (Mulsant) <i>Hylurgus ligniperda</i> (F) and <i>Hylastes ater</i> (Paykull) adults

The adult stages of three key New Zealand forest pests burnt pine longhorn beetle (Arhopalus ferus) goldenhaired bark beetle (Hylurgus ligniperda) and black pine bark beetle (Hylastes ater) were fumigated at 10 or 20C for 4 h to determine their mortalities at increasing dosages of methyl bromide as a first step towards developing a new fumigation schedule for New Zealand export logs Hylastes adults were the most methyl bromide tolerant methyl bromide concentration required to control Hylastes adults is much lower than the phytosanitary requirement for export logs to India and China which requires 120 g/m3 for for logs exported from New Zealand but further work on other life stages is required

Multigene phylogenies of Ophiostomataceae associated with Monterey pine bark beetles in Spain reveal three new fungal species

Ophiostoma species, some of which cause sapstain in timber and/or are mild pathogens, are common fungal associates of bark beetles (Coleoptera: Scolytinae). Three new Ophiostomataceae from Spain are recognized in the present study based on comparisons of sequence data for three gene regions as well as morphological characteristics. The new taxa are described as Ophiostoma nebulare sp. nov., Ophiostoma euskadiense sp. nov. and Graphilbum crescericum sp. nov.

Description of Phloeosinus laricionis sp. n. (Coleoptera: Curculionidae, Scolytinae), a new bark beetle species from southern Europe.

We describe a new species of pine bark beetle, Phloeosinus laricionis, associated with a pine decline recently affecting young plantations of Pinus nigra ssp. laricio Poiret growing on the Etna volcano, Sicily (South Italy). The new species is morphologically close to the group species of P. cedri Brisout, P. acatayi Schedl, and P. pfefferi Knížek, having all odd interstriae on the declivity of elytra bearing small, individual, sparse, more or less sharply pointed tubercles in males, or with smaller sparse blunt, nippled tubercles in females. While the other species of the same group live on cedars, the new species is the only Palaearctic Phloeosinus known from pine.

The promise [and uncertainties] of Biochar

The promise [and uncertainties] of Biochar

Cost sharing for pre-commercial thinning in southern pine plantations: Willingness to participate in Virginia's pine bark beetle prevention program

Forest management that reduces southern pine beetle (SPB) risk benefits not only the landowners, but all who draw benefits from southern pine forests, including other owners whose risk is reduced by landscape-wide efforts. One such practice is pre-commercial thinning (PCT) of pine stands, which may be unattractive to landowners due to substantial upfront costs and delayed or uncertain financial return. Because societal benefits are not fully realized by those who implement PCT, there may be a market externality whereby it is underprovided. Virginia's Pine Bark Beetle Prevention Program attempts to correct this externality by reimbursing a portion of PCT costs. To examine the efficacy of cost sharing in promoting participation, a survey was sent to 1200 NIPF landowners in Virginia, where southern pine is prevalent and SPB is a concern. Willingness to participate is measured using a referendum-style question for PCT on a hypothetical, qualifying property over a cost-share range of 20% to 90%. Results of discrete choice models indicate that cost sharing has a significant, positive effect on willingness to participate overall, though results indicate that increasing reimbursement above the 50% level is unlikely to increase participation substantively. Education and ownership preferences are also significant predictors of willingness to participate, with potential implications for program targeting and marketing.

Saproxylic community, guild and species responses to varying pheromone components of a pine bark beetle

Some bark beetle species (Coleoptera: Scolytinae) produce aggregation pheromones that allow coordinated attack on their conifer hosts. As a new saproxylic habitat is founded, an assemblage of associated beetles kairomonally respond to bark beetle infochemicals. Ips sexdentatus is one of the major damaging insects of Pinus spp. in Southern Europe. Its response to varying ipsenol (Ie) percentages in relation to ipsdienol (Id) was studied in northwestern Spain, along with the entire saproxylic beetle assemblage captured at multiple-funnel traps. Response profile modeling was undertaken for I. sexdentatus sexes and sex-ratios, associated species and for selected trophic groups using a reference Gaussian model. In addition, the effects on the saproxylic assemblages were analyzed. I. sexdentatus response curve peaked at 22.7% Ie content, while remaining taxa that could be modeled, peaked above ca. 40% Ie. Predator guilds showed a linear relationship with Ie proportion, while competitors showed a delayed response peak. Consequently, species assemblages differed markedly between varying pheromone component mixtures. Given that the evaluated pheromonal proportions mimicked that of logs being colonized by I. sexdentatus, results suggested that the registered differential responses at different levels might provide I. sexdentatus with a temporal window that maximizes conspecific attraction while reducing interference with competitor and predatory guilds. Described responses might help improve the monitoring of the population status of target bark beetles and their associates, but also point toward the by-catch of many natural enemies, as well as rare saproxylic beetle species, interfering with the aims of sustainable forest management.

Field Evaluations of Subterranean Termite Preference for Sap-Stain Inoculated Wood

Few studies have focused on interactions between subterranean termites and the ophiostomatoid fungal associates of pine bark beetles or root feeding weevils. Field stake tests were employed at four locations throughout Mississippi to determine the feeding preference of subterranean termites for blue-stained, unstained, and partially decayed southern pine sapwood stakes. This study also utilized wood decayed by Gloeophyllum trabeum, a fungus previously shown to elicit a positive subterranean termite feeding response, as a positive control. Stakes inoculated with G. trabeum received significantly more attacks than all other treatments after 16 weeks. Of the stakes attacked by subterranean termites, stakes inoculated with Ophiostoma minus were degraded faster than any other treatment. Subterranean termite preference for stakes treated with either of two Leptographium spp. and the untreated negative controls did not differ; however, each was fed upon less than all other treatments. The feeding rate on stakes inoculated with O. ips and G. trabeum being fed upon by subterranean termites was not significantly different. These results represent the first evidence of wood containing non-structurally degrading fungi (O. ips and O. minus) eliciting a feeding preference from subterranean termites greater than that of decayed wood. The implications of these results are particularly relevant to pine forest ecology, nutrient cycling, subterranean termite control, and the utilization of blue-stained southern pine building products in the southeastern U.S.

Molecular evidence of facultative intraguild predation by Monochamus titillator larvae (Coleoptera: Cerambycidae) on members of the southern pine beetle guild

The southern pine bark beetle guild (SPBG) is arguably the most destructive group of forest insects in the southeastern USA. This guild contains five species of bark beetles (Coleoptera: Curculionidae: Scolytinae): Dendroctonus frontalis, Dendroctonus terebrans, Ips avulsus, Ips calligraphus, and Ips grandicollis. A diverse community of illicit receivers is attracted to pheromones emitted by the SPBG, including the woodborers Monochamus carolinensis and Monochamus titillator (Coleoptera: Cerambycidae). These woodborers have been traditionally classified as resource competitors; however, laboratory assays suggest that larval M. carolinensis may be facultative intraguild predators of SPBG larvae. This study used polymerase chain reaction (PCR)-based molecular gut content analyses to characterize subcortical interactions between M. titillator and members of the SPBG. The half-lives of SPBG DNA were estimated in the laboratory prior to examining these interactions in the field. A total of 271 field-collected M. titillator larvae were analyzed and 26 (9.6%) tested positive for DNA of members of the SPBG. Of these larvae, 25 (96.2%) tested positive for I. grandicollis and one (3.8%) for I. calligraphus. Failure to detect D. terebrans and D. frontalis was likely due to their absence in the field. I. avulsus was present, but primers developed using adult tissues failed to amplify larval tissue. Results from this study support the hypothesis that larval Monochamus spp. are facultative intraguild predators of bark beetle larvae. Additionally, this study demonstrates the capabilities of PCR in elucidating the interactions of cryptic forest insects and provides a tool to better understand mechanisms driving southern pine beetle guild population fluctuations.

An improved lure for trapping the bark beetle Dendroctonus armandi (Coleoptera: Scolytinae)

The pine bark beetle, Dendroctonus armandi, is a native pest restricted to forests in the Qinling Mountains in China. There was an outbreak of this species there that affected over 0.36 million hectares of pine forest. We hypothesized that there are differences between the numbers of beetles captured by traps baited with various combinations of candidate semiochemicals extracted from the hindguts of D. armandi. In order to determine whether a better operational lure could be developed for D. armandi, we analyzed the volatiles in extracts of the hindgut of D. armandi and tested various combinations of candidate semiochemicals. The GC-MS and GC-FID analyses of volatiles in the extracts of the hindguts of D. armandi collected at different stages of the attack revealed that they are mainly a-pinene, b-caryophyllene and (+)-3-carene with minor amounts of myrcene, limonene, verbenol and verbenone. We tested various combinations of these candidate semiochemicals in order to determine an optimal blend. Our results suggest that the addition of b-caryophyllene to either a-pinene, or blends of a-pinene and other candidate semiochemicals, significantly enhanced the attractiveness of the lures for D. armandi. Field trapping experiments indicated that the blends that included b-caryophyllene, myrcene and other candidate semiochemicals resulted in significantly higher trap catches (161-243% higher) than a-pinene alone. Therefore, a simple lure consisting of a-pinene and b-caryophyllene would be an optimal blend for D. armandi. We conclude that this blend of semiochemicals may provide a better method of reducing the numbers of D. armandi in forest ecosystem.

Preference of Formosan Subterranean Termites for Blue-Stained Southern Yellow Pine Sapwood

Little research has been conducted to investigate interactions between the invasive Formosan subterranean termite, Coptotermes formosanus Shiraki, and pine bark beetles native to the southeastern United States. Facilitative interactions between these organisms could alter stand dynamics and impact wood utilization strategies. American Wood Protection Association Standard E1-09 choice tests were carried out to determine the feeding preference of Formosan subterranean termites for blue-stained versus unstained southern yellow pine sapwood. Three separate colonies of Formosan subterranean termites consumed on average twice as much air-dried blue-stained southern yellow pine sapwood over unstained air-dried controls. Additionally, Formosan subterranean termites consumed over five-times more kiln-dried blue-stained sapwood than unstained kiln-dried control wafers. The implications of these results are particularly relevant to pine forest ecology, nutrient cycling, and the utilization of blue-stained southern pine building products in the southeastern United States, where Formosan subterranean termites have become established.

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

AbstractThe identification and description of the chemical signals involved in the aggregation of bark beetles may lead to the development of integrated pest management strategies using synthetic pheromones. Ips sexdentatus Boern. (Col.: Scolytinae) colonizes trees of the Pinus genus across Europe, causing severe damage in occasions. The effect of cis‐verbenol, ipsenol, 2‐methyl‐3‐buten‐2‐ol (MB) and myrtenol in relation to the major pheromonal compound ipsdienol on the aggregation behaviour of I. sexdentatus was studied on four field bioassays. The ternary blend of racemic ipsdienol, cis‐verbenol and racemic ipsenol consistently caught the highest number of bark beetles, resulting in large standardized mean differences (dunbiased > 0.8). The binary blends between ipsdienol and ipsenol, and ipsdienol and cis‐verbenol also improved the performance of ipsdienol, although only ipsenol did it significantly. On the other hand, catches were reduced (dunbiased = −0.96) when MB was released along ipsdienol, although the effect was found to be non‐significant. On a third bioassay, the relative release rates between ipsdienol, ipsenol and cis‐verbenol were studied. Although no differences were found between the ternary blends, a ratio of 1 : 0.25 : 0.5 for ipsdienol, ipsenol and cis‐verbenol, respectively, scored the strongest effect size (dunbiased = 1.17). A fourth bioassay studied the behavioural effects of myrtenol and found no significant modifications to previously established findings. Myrtenol on its own attracted almost no individuals of I. sexdentatus. High numbers of bark beetle predators Thanasimus formicarius L. and Temnochila caerulea Olivier were trapped during the trials. The binary blend between ipsdienol and ipsdienol was shown to catch the highest significant amount of T. formicarius, whereas numbers of T. caerulea caught were highest on the binary blend between cis‐verbenol and ipsdienol. Presented results establish the ternary blend between ipsdienol, ipsenol and cis‐verbenol as a reference functional aggregative lure ready to be used on the management of I. sexdentatus.

Life-history traits promoting outbreaks of the pine bark beetle Ips acuminatus (Coleoptera: Curculionidae, Scolytinae) in the south-eastern Alps

The pine bark beetle Ips acuminatus has recently increased frequency and intensity of outbreaks in Pinus sylvestris stands in the Alps. During a 3-year period, we investigated life-history traits of the species that may have adaptive value. In the south-eastern Alps, I. acuminatus becomes active in early spring when the air temperature reaches 14°C, suggesting the presence of a local population adapted to low temperature. Such an early emergence allows the complete development of a second generation, even if only a portion of the population is truly bivoltine. As a consequence, there are two main attack periods, the first in early spring and the second in summer, resulting in different trees being colonised each time. Irrespective of the generation, a large part of the beetles leaves the breeding substrate before hibernation, and this is interpreted as an escape from natural enemies associated with the bark. These findings suggest that the populations of I. acuminatus of the south-eastern Alps may benefit from climate warming as they have more opportunities to complete the second generation and to escape from mortality factors associated with a long permanence in the bark. In addition, the extended period of tree colonisation offers more possibilities to locate suitable hosts and to build up outbreak densities.

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

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.

Effectiveness of Cedar Oil Products for Preventing Host Use by Ips avulsus (Eichhoff) (Coleoptera: Curculionidae) in a Modified Small-Bolt Assay

Insecticide products based on cedar oil are readily available, but evaluations against pine bark beetles (Coleoptera: Curculionidae: Scolytinae) are lacking. In the southeastern U.S., the southern pine beetle, Dendroctonus frontalis Zimm, is the major bark beetle pest for which tree protectants are applied. However, Ips avulsus (Eichhoff) are more consistently available, are easily trapped and can attain pest status at times, making them an attractive option for the evaluation of certain tree protection products. In this study, we evaluated 2 commercial cedar oil products for their ability to prevent attack by I. avulsus on loblolly pine (Pinus taeda L.) bolts. The field method we deployed was an extension of a previously developed laboratory method in which small-bolts are treated with the product and provided a challenge by adult beetles. The new method used multiple-funnel traps baited with synthetic attractants to direct I. avulsus to test bolts. The method was successful in providing a challenge to treatments with I. avulsus, and resulted in neither product being consistently effective for preventing bolt utilization by this beetle. Although not considered effective in the majority of our trials, full-strength (neat) application of cedar oil product reduced bolt utilization by I. avulsus during winter trials (November and February), perhaps due to lower attack pressure from beetles. Evaluations at other times of the year (March through May), or that began > 0 days post-application, resulted in the products consistently failing to meet either of our efficacy criteria. Compared with competing insecticide products (e.g., those based on bifenthrin), the cedar oil products appear to be less effective, require more frequent reapplication and be more expensive.

Pinus pinaster Ait. tree mortality following wildfire in Spain

Maritime pine ( Pinus pinaster Ait.) is the tree species most affected by wildfire in the Iberian Peninsula. Prediction of the probability of fire-injured tree mortality is critical for management of burned areas, evaluation of the ecological and economic impact of wildfire and prescribed fire planning and application. Pine bark beetles (Scolytidae) frequently attack burned maritime pine stands and cause extensive post-fire mortality throughout the Iberian Peninsula. In the present study, maritime pine trees were monitored for three years following 14 wildfires in four ecotypes in Spain (11 fires in Galicia (Galician ecotype – NW Spain), one fire in Portillo (Meseta-Castellana ecotype – Central Spain), one fire in Rodenal (Rodenal ecotype – Central Spain), and one fire in Genalguacil (Sierra Bermeja ecotype – SW Spain)). Data on tree attributes, crown and bole injury, ground fire severity, Ips sp. presence and tree survival were obtained by examining 3085 trees. Logistic regression models for predicting the probability of delayed maritime pine mortality were developed by use of generalized estimated equations (GEE). An ample range of response to fire damage in mortality was evident among the four ecotypes and different models were fitted for each. The most important variables for predicting tree mortality were total crown volume damaged, presence of Ips sp. attack and cambium kill rating. The results highlight the extensive presence of Ips sp. in burned maritime pine forests and its importance in tree mortality process, the ample range of response of P. pinaster, in terms of post-fire mortality, as well as the need to develop site specific mortality models for the different ecotypes of this species following fire.

Woodpeckers increase in abundance but maintain fecundity in response to an outbreak of mountain pine bark beetles

Many temperate woodpecker species are thought to be highly conservative in their fecundity with little response to fluctuations in availability of resources. In a 15-year field study in interior British Columbia, we evaluated responses in abundance and fecundity of six species of resident and migrant woodpeckers (downy woodpecker [ Picoides pubescens], hairy woodpecker [ Picoides villosus], American three-toed woodpecker [ Picoides dorsalis], pileated woodpecker [ Drycopus pileatus], northern flicker [ Colaptes auratus], and red-naped sapsucker [ Sphyrapicus nuchalis]) to a large-scale outbreak of mountain pine bark beetles that resulted in a strong positive pulse in food supply. Population densities of woodpecker species increased during outbreak years. Despite the year-round multi-annual increase in food resources, and in contrast to the strong increases in fecundity shown by nuthatches and chickadees, annual fecundity (as indicated by clutch size and number of nestlings that fledged) did not change for any woodpecker species over the study. Similarly, we found no changes in fecundity in response to selective forest harvesting despite numerical increases for woodpeckers at these sites. Our study confirms that these woodpecker species are conservative in their reproductive investment patterns even during strong multi-annual increases in food. Our findings indicate woodpecker populations are regulated numerically through variable survival and/or greater immigration rates, which can result in higher breeding densities temporarily during resource pulses.