A comparison of heat pulse velocity and lesion lengths for assessing the relative virulence of mountain pine beetle‐associated fungi on jack pine

The mountain pine beetle (MPB) vectors three blue‐stain fungi, Grosmannia clavigera, Ophiostoma montium and Leptographium longiclavatum, which contribute to the success of the beetles and the death of the trees. The utility of two methods, heat pulse velocity (HPV) and lesion length, for assessing the relative virulence of these fungi were compared on jack pine in central Alberta. The HPV monitoring apparatus failed to detect xylem sap flow in any of the trees and, thus, could not be used to assess fungal virulence. In contrast, measurement of lesion lengths was more sensitive and provided further evidence that G. clavigera and L. longiclavatum are more virulent than O. montium. The failure of the HPV apparatus to detect sap flow suggests that the study trees were moisture stressed, a factor likely to increase their susceptibility to MPB. Thus, this method is not appropriate for assessing the response of the most susceptible (i.e. drought stressed) trees to MPB and its associated fungi.     

Mountain pine beetle scarring of lodgepole pine in south-central Oregon

Three forest disturbance periods, 1973—present, 1922–1929, and 1827–1946 were determined by aging scars on stems of lodgepole pine trees. All of the scars from the 1970's and 1920's, and most of the scars from the 1820's–40's were determined to be caused by the mountain pine beetle. A few scars from the earliest period may be the result of fire. Diagnostic characteristics of beetle scars are: resemblance to fire scars, pitch tubes, beetle emergence holes, blue stain, beetle galleries, retained bark on the scar face, and an orange or red discoloration around healthy sapwood. Beetle attacks tend to have a northeastern aspect and extend approximately two-thirds around tree boles at breast height.By recognizing beetle scars it is possible to accurately age previous mountain pine beetle attacks. Many scars which had been thought to be of fire origin are actually caused by the mountain pine beetle.     

Monitoring the impacts of mountain pine beetle mitigation

Since 1999, the mountain pine beetle (Dendroctonus ponderosae Hopk. [Coleoptera: Scolytidae]) has impacted over 13 million hectares of pine forests in western Canada. Successful mitigation of the beetle depends on the accurate and timely identification of currently infested trees and on sustained control activities over several successive years. We monitored the success of mitigation activities in reducing damage caused by mountain pine beetle at two sites (A and B) on the leading edge of the current beetle epidemic in western Canada. Using three years of digital high spatial resolution aerial imagery (2006–2008) and one season of field measurements (2008), we estimated retrospective ratios of trees attacked by beetle in the current year (green attack) to trees attacked in the previous year (red attack), hereafter referred to as G:R. Our results indicate that mitigation activities slowed the rate of population growth, with G:R found to be decreasing or stable over sites A and B while mitigation was ongoing in 2005 and 2006 (site A 1.06:1; site B 0.32:1). When mitigation was discontinued over site A in 2007, the G:R increased markedly (1.94:1), while continued mitigation at site B in 2007 further reduced the G:R (0.22:1). Despite the cost associated with mitigation, its efficacy is rarely assessed and even more rarely documented. The approach presented herein enables a sample-based appraisal of mitigation efforts.     

Susceptibility of ponderosa pine, Pinus ponderosa (Dougl. ex Laws.), to mountain pine beetle, Dendroctonus ponderosae Hopkins,attack in uneven-aged stands in the Black Hills of South Dakota and Wyoming USA

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.     

Response of bark beetles and their natural enemies to fire and fire surrogate treatments in mixed-conifer forests in western Montana

Four treatments (control, burn-only, thin-only, and thin-and-burn) were evaluated for their effects on bark beetle-caused mortality in both the short-term (one to four years) and the long-term (seven years) in mixed-conifer forests in western Montana, USA. In addition to assessing bark beetle responses to these treatments, we also measured natural enemy landing rates and resin flow of ponderosa pine (Pinus ponderosa) the season fire treatments were implemented. All bark beetles were present at low population levels (non-outbreak) for the duration of the study. Post-treatment mortality of trees due to bark beetles was lowest in the thin-only and control units and highest in the units receiving burns. Three tree-killing bark beetle species responded positively to fire treatments: Douglas-fir beetle (Dendroctonus pseudotsugae), pine engraver (Ips pini), and western pine beetle (Dendroctonus brevicomis). Red turpentine beetle (Dendroctonus valens) responded positively to fire treatments, but never caused mortality. Three fire damage variables tested (height of crown scorch, percent circumference of the tree bole scorched, or degree of ground char) were significant factors in predicting beetle attack on trees. Douglas-fir beetle and pine engraver responded rapidly to increased availability of resources (fire-damaged trees); however, successful attacks dropped rapidly once these resources were depleted. Movement to green trees by pine engraver was not observed in plots receiving fire treatments, or in thinned plots where slash supported substantial reproduction by this beetle. The fourth tree-killing beetle present at the site, the mountain pine beetle, did not exhibit responses to any treatment. Natural enemies generally arrived at trees the same time as host bark beetles. However, the landing rates of only one, Medetera spp., was affected by treatment. This predator responded positively to thinning treatments. This insect was present in very high numbers indicating a regulatory effect on beetles, at least in the short-term, in thinned stands. Resin flow decreased from June to August. However, resin flow was significantly higher in trees in August than in June in fire treatments. Increased flow in burned trees later in the season did not affect beetle attack success. Overall, responses by beetles to treatments were short-term and limited to fire-damaged trees. Expansions into green trees did not occur. This lack of spread was likely due to a combination of high tree vigor in residual stands and low background populations of bark beetles.     

Logistics of supplying biomass from a mountain pine beetle-infested forest to a power plant in British Columbia

Abstract

The search for alternative energy sources has increased the interest in forest biomass. During the past few years, the severe infestation of the mountain pine beetle (MPB) within the forests of interior British Columbia (BC) has led to huge volumes of dead wood that exceed the capacity of the lumber industry. One way to make the most value of the surplus wood is to use it as the feedstock for bioenergy. The high costs associated with harvest and transport, and uncertainty in supply logistics are issues related to forest biomass utilization. This paper presents the development of a forest biomass supply logistics simulation model and its application to a case of supplying MPB-killed biomass from Quesnel timber supply area (one of the most infested areas in the interior BC) to a potential 300 MW power plant adjacent to the city of Quesnel. It provides values of quantity, cost and moisture content of biomass which are important factors in feasibility study of bioenergy projects. In the case of a conventional harvesting system, the biomass recovered from roadside residues in 1 year will meet only about 30% of the annual demand of the power plant with an estimated delivered cost of Can $45 per oven-dry tonne of woodchips. Sensitivity analyses were also performed.     

Recruitment limitation in forests: Lessons from an unprecedented mountain pine beetle epidemic

Since the mid-1990s the forests of central British Columbia have undergone an unprecedented Mountain Pine Beetle (Dendroctonus ponderosae Hopkins) (MPB) epidemic that has resulted in extensive mortality of canopy lodgepole pine (Pinus contorta var. latifolia Engelm.). This study investigated how seed-source availability, seedbed substrate, overstory structure, and time since MPB attack interact to affect post-MPB seedling recruitment of the dominant tree species of these forests. In addition to post-MPB recruitment, these forests may be regenerated by trees established in the understory prior to MPB disturbance. Accordingly, we examined abundance and patterns of all regeneration less than 130 cm tall. We found post-MPB recruitment was sparse. Subalpine fir (Abies laciocarpa (Hook.) Nutt.) comprised the majority of the post-MPB recruitment. It increased with local parent tree basal area and increased strongly with proximity to a major seed source. This resulted in a patchy distribution for subalpine fir post-MPB regeneration. Lodgepole pine post-MPB recruitment was limited by overstory shading. Recruitment of pine decreased as the total overstory basal area increased. Interior spruce (Picea glauca × engelmannii) post-MPB recruitment was similarly limited by total overstory basal area. Seedbed substrates were uniform and dominated by moss. Substrate type distribution did not change as time since MPB disturbance increased. The overall low post-MPB recruitment observed was likely due to a lack of disturbance to the moss-dominated forest floor. Moss is known to be a poor substrate in northern forests. The distribution of all regeneration less than 130 cm tall showed the same trends as the post-MPB regeneration. We believe the post-MPB seedling recruitment dynamics of these forests was not substantially changed from conditions prior to MPB disturbance. There was no pulse of regeneration up to 10 years post-MPB disturbance. Unless this changes, future stand structure will be dominated by the seedling bank established prior to the MPB epidemic. Subalpine fir dominated the seedling bank (68%) and post-MPB recruitment (94%). This suggests that MPB-disturbed forests are undergoing a substantial shift in landscape-level species composition.     

Effects of mountain pine beetle (Dendroctonus ponderosae Hopkins) infestations on forest stand structure in the southern Canadian Rocky Mountains

Forests in the montane and lower subalpine ecoregions of the southern Canadian Rocky Mountains may have been more open and structurally diverse at the beginning of the 20th Century than today. Today, the area of mature Pinus contorta subsp. latifolia Dougl. forest that is conducive to mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins) infestations, infrequent high severity fires, and herbivory appears to have increased in Banff and Kootenay National Parks. Based on a review of the literature, we hypothesised that MPB infestations increase forest stand structural diversity and tree species diversity. Stand structure parameters were investigated in mesic montane and lower subalpine stands approximately 15, 25, and 65 years after MPB outbreaks. Parameters measured were stand density (number of trees per ha), diameter at breast height, height class, species, age class distribution, and coarse woody debris mass. Influences of fire frequency, time since fire, and fire severity on these parameters were assessed to determine whether fire history had a confounding influence on stand structure. The Shannon–Wiener index indicated higher stand structural diversity 15 years but not 25 and 65 years after MPB infestations. MPB infestations led to general decreases within stands in the number of living trees, small diameter snags, and Pinus tree species and an increase within stands in the number of large diameter snags. Management that allows the occurrence of the natural fire regime of variable severity fires, in addition to some MPB infestations, would provide for more open and diverse stands. MPB infestations have some effects on stand structure that are similar to those of fire. Changes in stand structure resulting from recent declines in burning rates within Banff and Kootenay National Parks can be reversed to some extent by MPB infestations.     

Dielectric spectroscopy of Scots pine

Dielectric properties of Scots pine (42 trees) were compared with density, moisture content (MC), and resin acid content (RAC) (of heartwood). The samples were measured in frozen, green, conditioned and non-conditioned dry moisture states to evaluate the potential of dielectric spectroscopy in determining the wood characteristics at different stages of wood processing. Heartwood and sapwood parts of each sample were measured separately, and through-transmission measurement was conducted in longitudinal and tangential direction at frequencies from 1 MHz to 1 GHz. The MC and density correlated significantly with the dielectric parameters in both measurement directions but especially in longitudinal direction. The RAC of the heartwood correlated significantly with tanδ and ε″/(ε′ ? 1) of the green samples measured in the tangential direction at frequencies above 200 MHz. The correlation at 1 GHz was ?0.56 for green samples, ?0.66 for conditioned samples and ?0.61 for non-conditioned samples (P < 0.001, for all). The study suggests that the extractives also affect radio-frequency dielectric responses, which might be used for extractive analyses of pine heartwood.     

Mountain pine beetle‐associated blue‐stain fungi in lodgepole × jack pine hybrids near Grande Prairie,Alberta (Canada)

The mountain pine beetle (MPB), the most serious pest of lodgepole pine in mountainous western Canada, spread northeastward into lodgepole × jack pine hybrids in the boreal forest of Alberta in 2006. The MPB vectors three species of blue‐stain fungi, which contribute to the success of the beetles. These fungi were isolated from MPB larvae and galleries in several lodgepole × jack pine stands in the Grande Prairie region of northwestern Alberta in autumn 2006 and winter and spring 2007. Fungi were recovered from more than 95% of gallery systems. The three fungi were similarly prevalent but Ophiostoma montium was the most frequently isolated fungus at each sampling point, isolated from 72% to 90% of gallery systems compared with 63% to 78% for Grosmannia clavigera, and 61% to 86% for Leptographium longiclavatum. Ophiostoma montium and G. clavigera were isolated from more larvae than gallery samples, with the opposite true for L. longiclavatum. Most gallery systems contained multiple fungi with three fungi per gallery system being more common in autumn and winter and two fungi more common in the spring. The combination of G. clavigera and L. longiclavatum was less common among gallery systems with two fungi than either of the pairwise combinations containing O. montium. Fungal prevalence was the same above and below snow level. The prevalence of the three fungi did not differ significantly among stands sampled in the spring but stands with more G. clavigera tended to have less L. longiclavatum. The winter of 2006–2007 was colder than average throughout Alberta with temperatures below ?30°C in November, January and February, and all three fungi were present after the cold winter while most larvae had died, suggesting that overwintering mortality of the fungi will not limit persistence and spread of MPB in the boreal forest.     

Response of Japanese red pine to inoculation with a blue stain fungus,Ceratocystis piceae

To confirm the pathogenicity of a blue stain fungus,Ceratocystis piceae (Münch) Bakshi to the Japanese red pine (Pinus densiflora Sieb. et Zucc.), the responses of healthy young pine trees and stressed trees which were girdled by the half-circumferential girdling technique were investigated by the fungal inoculation test. Although neither of the pine trees inoculated withC. piceae in the non-girdled treatment nor the controls died, mortality of the trees girdled and inoculated withC. piceae was 28.6%. In the pine trees inoculated withC. piceae, the mean area of the necrotic lesion of the sapwood was significantly larger than that of the controls, and the mean of the water pressure potential of the xylem decreased, regardless of the girdling treatment. TheC. piceae was reisolated from the wood pieces near the inoculation points on the inoculated trees, but not from the controls. These results suggest that under strongly stressed conditions, the Japanese red pine trees might have been killed by heavy infestations ofC. piceae carried by bark beetles. A part of this paper was presented at the 103rd Annual Meeting of the Japanese Forestry Society (1992).     

Influence of fire and mountain pine beetle on the dynamics of lodgepole pine stands in British Columbia,Canada

An outbreak of the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB), currently affecting over 10.1 million hectares of lodgepole pine forests (Pinus contorta Dougl.) in British Columbia, Canada, is the largest in recorded history. We examined the dynamics of even-aged lodgepole pine forests in southern British Columbia, which were undergoing this MPB outbreak. Using dendroecology and forest measurements we reconstructed the stand processes of stand initiation, stand disturbances, tree mortality, and regeneration, and explained the current stand structure and the potential MPB impacts in selected stands. Our results indicate that stand-replacing fires initiated even-aged seral lodgepole pine stands in this region. In the absence of fire in the 20th century, multiple MPB disturbances, which each resulted in partial canopy removal, modified the simple one-layer structure of the fire-origin stands by the initiation of post-MPB disturbance regeneration layers, transforming the stands into complex, multi-aged stands. Despite high overstory mortality due to the current MPB outbreak, regeneration layers, which are likely to survive the current outbreak, will provide important ecological legacies and will contribute to mid-term timber supply.     

The effects of mechanical fuel reduction treatments on the activity of bark beetles (Coleoptera: Scolytidae) infesting ponderosa pine

Selective logging, fire suppression, forest succession and climatic changes have resulted in high fire hazards over large areas of the western USA. Federal and state hazardous fuel reduction programs have increased accordingly to reduce the risk, extent and severity of these events, particularly in the wildland–urban interface. In this study, we examined the effects of mechanical fuel reduction treatments on the activity of bark beetles in ponderosa pine, Pinus ponderosa Dougl ex. Laws., forests located in Arizona and California, USA. Treatments were applied in both late spring (April–May) and late summer (August–September) and included: (1) thinned biomass chipped and randomly dispersed within each 0.4 ha plot; (2) thinned biomass chipped, randomly dispersed within each plot and raked 2 m from the base of residual trees; (3) thinned biomass lopped-and-scattered (thinned trees cut into 1–2 m lengths) within each plot; (4) an untreated control. The mean percentage of residual trees attacked by bark beetles ranged from 2.0% (untreated control) to 30.2% (plots thinned in spring with all biomass chipped). A three-fold increase in the percentage of trees attacked by bark beetles was observed in chipped versus lopped-and-scattered plots. Bark beetle colonization of residual trees was higher during spring treatments, which corresponded with peak adult beetle flight periods as measured by funnel trap captures. Raking chips away from the base of residual trees did not significantly affect attack rates. Several bark beetle species were present including the roundheaded pine beetle, Dendroctonus adjunctus Blandford (AZ), western pine beetle, D. brevicomis LeConte (AZ and CA), mountain pine beetle, D. ponderosae Hopkins (CA), red turpentine beetle, D. valens LeConte (AZ and CA), Arizona fivespined ips, Ips lecontei Swaine (AZ), California fivespined ips, I. paraconfusus Lanier (CA) and pine engraver, I. pini (Say) (AZ). Dendroctonus valens was the most common bark beetle infesting residual trees. A significant correlation was found between the number of trees chipped per plot and the percentage of residual trees with D. valens attacks. A significantly higher percentage of residual trees was attacked by D. brevicomis in plots that were chipped in spring compared to the untreated control. In lopped-and-scattered treatments, engraver beetles produced substantial broods in logging debris, but few attacks were observed on standing trees. At present, no significant difference in tree mortality exists among treatments. A few trees appeared to have died solely from D. valens attacks, as no other scolytids were observed in the upper bole. In a laboratory study conducted to provide an explanation for the bark beetle responses observed in this study, monoterpene elution rates from chip piles declined sharply over time, but were relatively constant in lopped-and-piled treatments. The quantities of β-pinene, 3-carene, -pinene and myrcene eluting from chips exceeded those from lopped-and-piled slash during each of 15 sample periods. These laboratory results may, in part, explain the bark beetle response observed in chipping treatments. The implications of these results to sustainable forest management are discussed.     

The temperature and moisture content in lumber during preheating and drying

Summary The time required to thoroughly preheat/presteam green 8/4 (51 mm) thick red pine and white birch lumber was determined. Thermocouples imbedded in the centre of samples were used to determine presteaming/preheating times for experimental material. These data were then compared to time determined by analytical methods (using formulae developed by Kollmann). No significant differences were found.During the subsequent drying period data were collected on interior wood temperature, mousture content and gradient. Results of the drying tests indicated: i) interior temperature increases in direct relation to elapsed time, ii) moisture content drops exponentially with elapsed time, and iii) an exponential relationship exists between average moisture content and the core temperature of the lumber.Results indicate that monitoring of the lumber drying process through measurements of interior wood temperature may be feasible.The first author was visiting Canada under the Chinese Scholar Program established by the Council of Ministers of Education, Canada. His research work was carried out at Forintek Canada Corp., Eastern Laboratory, OttawaThe authors would like to acknowledge the assistance and support of the following: Dr. M. Y. Cech, Manager, Lumber Manufacturing Technology, Forintek Canada Corp., Eastern Forest Products Laboratory-Senior Project Supervisor, and Mr. F. Pfaff, Research Scientist, Forintek Canada Corp     

Relationship between the incidence of pine wilt disease and the drainage area

We examined the relationship between the incidence of pine wilt disease and moisture conditions in the stand level ofPinus densiflora Sieb. et Zucc. forests in the warm-temperate zone of the western part of Japan. For this analysis, pine trees killed by pine wilt disease were distinguished from the suppressed trees by their position in the layer of the pine forest stand. The drainage area, which is small in the upper part and large in the lower part of the slope, was adopted for representing the moisture conditions in the soil of the slope. The percentage of the pine trees killed by pine wilt disease increased as the size of the drainage area increased. This result suggested that the incidence of pine wilt disease tended to be high in areas with moist conditions. Pine trees attacked by the pinewood nematode die from extensive water deficit due to tracheid cavitations. Pine wilt disease mainly emerges in the summer when the soil water conditions become especially severe, and the radical water stress is thought to accelerate the disease. It was assumed that pine trees in the plots with the small drainage area resisted the influence of the attack of the pinewood nematode because pine trees in the plots with the small drainage area encountered long-term water stress and acquired drought tolerance. Pine trees in the plots with the large drainage area were presumed to be well established in the moist conditions and not to have acquired drought tolerance. The drought tolerance of pine trees was thought to be an important factor in resistance to pine wilt disease.     

The Pine Shoot Beetle Tomicus piniperda as a Vector of Blue Stain Fungi to Windblown Pine

After the great gale of 1987, the role of the pine shoot beetle,Tomicus piniperda, as a vector of blue stain fungi to windblownpine in southern England was examined by macerating adult beetlesand culturing the macerate on various agar media. Isolationswere also made from pine tissue associated with beetle galleriesand tunnels. Using data from between three and nine sites, it was found that17 per cent of the overwintered adult beetles were carryingfast-growing Leptographium spp. as they began to construct breedinggalleries in spring 1988. More than half the new generationof adult beetles were contaminated with these fungi when theyemerged in June-July 1988, but this proportion dropped as thelife cycle of shoot-feeding and overwintering progressed. Itaveraged 26 per cent at the time of brood gallery constructionin spring 1989. Isolations made from pine tissue around the galleries also showedchanges in the frequency of blue stain fungi. Of early broodgalleries 25 per cent yielded Leptographium, while the figurefor late galleries was 51 per cent. These results were consistentwith the direct introduction of Leptographium by the parentbeetles into some galleries, and the subsequent rapid hyphalgrowth of the fungus within the tree to colonize tissue adjacentto other galleries. The principal species identified was L. wingfieldii. However,L. lundbergii, L. huntii, L. procerum and an unidentified Leptographiumspecies were occasionally recorded, both on the beetles andin the trees. Graphium species were quite common also. In addition,the black yeasts, Hormonema dematioides and Aureobasidium pullulans,were frequently present, particularly in the pine shoot samples.     

Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood

Scots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168?h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18?months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks.     

Prescribed fire effects on bark beetle activity and tree mortality in southwestern ponderosa pine forests

Prescribed fire is an important tool in the management of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests, yet effects on bark beetle (Coleoptera: Curculionidae, Scolytinae) activity and tree mortality are poorly understood in the southwestern U.S. We compared bark beetle attacks and tree mortality between paired prescribed-burned and unburned stands at each of four sites in Arizona and New Mexico for three growing seasons after burning (2004–2006). Prescribed burns increased bark beetle attacks on ponderosa pine over the first three post-fire years from 1.5 to 13% of all trees, increased successful, lethal attacks on ponderosa pine from 0.4 to 7.6%, increased mortality of ponderosa pine from all causes from 0.6 to 8.4%, and increased mortality of all tree species with diameter at breast height >13 cm from 0.6 to 9.6%. On a per year basis, prescribed burns increased ponderosa pine mortality from 0.2% per year in unburned stands to 2.8% per year in burned stands. Mortality of ponderosa pine 3 years after burning was best described by a logistic regression model with total crown damage (crown scorch + crown consumption) and bark beetle attack rating (no, partial, or mass attack by bark beetles) as independent variables. Attacks by Dendroctonus spp. did not differ significantly over bole heights, whereas attacks by Ips spp. were greater on the upper bole compared with the lower bole. Three previously published logistic regression models of tree mortality, developed from fires in 1995–1996 in northern Arizona, were moderately successful in predicting broad patterns of tree mortality in our data. The influence of bark beetle attack rating on tree mortality was stronger for our data than for data from the 1995–1996 fires. Our results highlight canopy damage from fire as a strong and consistent predictor of post-fire mortality of ponderosa pine, and bark beetle attacks and bole char rating as less consistent predictors because of temporal variability in their relationship to mortality. The small increase in tree mortality and bark beetle attacks caused by prescribed burning should be acceptable to many forest managers and the public given the resulting reduction in surface fuel and risk of severe wildfire.     

Pine bark beetle problem in Japan,referring to the discovery of the pine wood nematode,Bursaphelenchus lignicolus (Mamiya & Kiyohara)

Heavy loss of pine trees has been occurring for several decades throughout central to southwestern districts of Japan. In spite of beetles abundantly found under bark of dead trees, entomologists were inclined to the assumption that some other agents had already infected healthy trees before beetle attack based on various findings. It has been proved recently that the causative agent was the pine wood nematode (Bursaphelenchus lignicolus) newly discovered by pathologists and its transmitter was the Japanese pine sawyer (Monochamus alternatus). Aerial application of insecticides against the sawyer is now employed as a tentative measure of control.     

Douglas-fir and western larch: chemical and physical properties in relation to Douglas-fir bark beetle attack

Frequency of Douglas-fir bark beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae), attack on western larch (Lark occidentalis Nutt.) was negatively correlated with 3-carene content of the xylem oleoresin. Concentrations of all oleoresin volatiles from stem cores of standing trees were higher in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) than in western larch with the single exception of 3-carene. Successful brood production by the Douglas-fir bark beetle in standing trees of Douglas-fir but not western larch may therefore be explained, at least in part, by the high 3-carene content of western larch. Other differences between the species that might affect susceptibility to beetle attack include thinner phloem, higher phloem moisture content and larger diameter vertical resin ducts in western larch compared with Douglas-fir. Live standing western larch had no oleoresin exudation pressure, suggesting that this trait is not associated with resistance to attack by the Douglas-fir bark beetle in this species.