Blue-stain Fungi Research Articles

Penetration of 3-iodo-2-propynyl butylcarbamate (IPBC) in coniferous wood pre-treated with Physisporinus vitreus

The permeability of Norway spruce wood can be reduced to 1–5% of that of green timber when dried, resulting in only slight radial penetration of chemical solutions. We investigated the penetration of the biocide 3-iodo-2-propynyl butylcarbamate, (IPBC) in Norway spruce and Scots pine sapwood when applied in a water-based coating system. Penetration of both untreated wood and specimens pretreated with the white-rot fungus Physisporinus vitreus was analyzed by the absence or presence of blue staining after incubation with Aureobasidiumpullulans and Sclerophoma pithyophila. The qualitative results were compared with quantitative data obtained by chemical analysis. It was assumed a pre-treatment with Physisporinus vitreus could make the surface of the substrate more porous and improve the penetration of fluid substances. All analytical investigations of the samples were done after an outdoor weathering period of 6 months. From a practical point of view the performance of the coated substrate is more relevant after a certain aging procedure then right after the application. The chemical measured uptake of IPBC for Scots pine was similar for all samples at the surface. The penetration depth was higher for those samples with a pre-treatment with Physisporinus vitreus. The colonization pattern of the samples by blue-stain fungi depended upon the pre-treatment but did not show a clear correlation between IPBC-content and staining. The cross-section of the samples with pre-treatment was completely stained, the cross-section of the samples without pre-treatment did show a distinctive blue stain-free zone. In Norway spruce, the chemical measured uptake of IPBC was similar for all samples at the surface independent of the pre-treatment. The penetration depth was higher for those samples with a pre-treatment with Physisporinus vitreus. But a clear visible colonization by blue-stain fungi was only observed for the samples with a pre-treatment with Physisporinus vitreus. The samples without pre-treatment were locally stained across the entire cross-section. As with the Scots pine, a clear correlation between IPBC-content and blue staining was not visible, following comparison of the samples with and without pre-treatment with Physisporinus vitreus. The results suggest that not only the presence of IPBC influences colonization by A.pullulans and S.pithyophila, but also a range of other factors in wood pre-treated with P. vitreus.

Automated image processing for quantification of blue-stain discolouration of Norway spruce wood

Bioincising is a promising method for enhancing liquid uptake (e.g. preservatives or wood-modification agents) in refractory wood. Incubation with the white-rot fungus, Physisporinus vitreus, which selectively degrades pit membranes, results in deeper and more homogeneous penetration of liquids. Conventional methods of assessing the degree of fungal discolouration of wood after treatment with preservatives (e.g. European standard EN 152) are partly based on a subjective rating scale, which gives a rough value of the surface colonisation by blue-stain fungi. Hence, an automated image processing (AIP) procedure was developed for standardised quantification of the segmentation thresholds of discolouration and tested against manual segmentation analysis. Using the red filter in the AIP method revealed high correlation (R 2 0.95) and allowed for more user friendly and objective determination of blue staining of wood.

Use of wax emulsions for improvement of wood durability and sorption properties

Waxes are used for treatment of wood surfaces for several decades predominately as surface treatments because they weakly penetrate into the wood. In order to overcome this issue, water emulsions were applied in the present experiment. Five water emulsions of various concentrations were used, namely montan wax, polyethylene, ethylene copolymer and oxidized polyethylene wax. Performance of wax treated beech (Fagus sylvatica) and Norway spruce (Picea abies) against white rot, brown rot and blue stain fungi was tested. In parallel, sorption properties of wax treated wood were determined. The treated specimens were more resistant to wood decay fungi. Polyethylene and oxidized polyethylene wax were found to be particularly efficient. Although this treatment does not improve resistance to blue stain fungi, it reduces the sorption of water.

Studies on a Blue Staining Fungus of Pinus luchuensis Mayr. Separated from Some Species of Pine Bark Beetles

Studies on a Blue Staining Fungus of Pinus luchuensis Mayr. Separated from Some Species of Pine Bark Beetles

Multilocus species identification and fungal DNA barcoding: insights from blue stain fungal symbionts of the mountain pine beetle

There is strong community-wide interest in applying molecular techniques to fungal species delimitation and identification, but selection of a standardized region or regions of the genome has not been finalized. A single marker, the ribosomal DNA internal transcribed spacer region, has frequently been suggested as the standard for fungi. We used a group of closely related blue stain fungi associated with the mountain pine beetle (Dendroctonus ponderosae Hopkins) to examine the success of such single-locus species identification, comparing the internal transcribed spacer with four other nuclear markers. We demonstrate that single loci varied in their utility for identifying the six fungal species examined, while use of multiple loci was consistently successful. In a literature survey of 21 similar studies, individual loci were also highly variable in their ability to provide consistent species identifications and were less successful than multilocus diagnostics. Accurate species identification is the essence of any molecular diagnostic system, and this consideration should be central to locus selection. Moreover, our study and the literature survey demonstrate the value of using closely related species as the proving ground for developing a molecular identification system. We advocate use of a multilocus barcode approach that is similar to the practice employed by the plant barcode community, rather than reliance on a single locus.

Ophiostomatoid fungi transported by Ips sexdentatus (Coleoptera; Scolytidae) in Pinus pinaster in NW Spain

Ips sexdentatus (Coleoptera; Scolytidae) is one of the main vectors of ophiostomatoid blue stain fungi that can cause mortality of healthy conifers. For this reason, our objective was to identify the fungal species carried by this bark beetle in Maritime pine (Pinus pinaster) in north-western Spain. We collected insects from naturally infected pines placed them on malt extract agar (MEA) and left to walk freely on culture plates. Plant tissues (phloem and xylem) from adult pines were cultivated in moist chambers and also on MEA. At the same time, we inoculated pine logs with living insects in the laboratory. Four ophiostomatoid fungi appeared: Ophiostoma ips, Ophiostoma brunneo-ciliatum, Ceratocystiopsis minuta and Ophiostoma sp., as well as Graphium and Sporothrix imperfect stages. Moreover there were seven saprophytic species: Penicillium sp., Trichoderma sp., Verticillium sp., Mucor sp., Aspergillus niger, Gliocladium viride and Scopulariopsis brevicaulis, and the pathogenic Ophiostoma ips. The fructification percentage of the ophiostomatoid species was low, however; its imperfect stage Sporothrix/Hyalorhinocladiella produced high quantity of conidiophores.

Biocontrol of decay in seasoning utility poles. I. Growth rate and colonizing ability of bluestain and decay fungi in vivo and in vitro

SummarySeasoning (air drying) of utility poles for 6–12 months is essential before preservative treatment can be achieved. However, during seasoning, pine sapwood is often colonized by decay fungi, thereby compromising the performance and service life of the poles. This study investigated the potential of bluestain fungi to act as short‐term biocontrol agents against decay during seasoning. An important attribute for biocontrol is rapid growth, so growth rates of common bluestain (Ceratocystis coerulescens, Ophiostoma minus, Ophiostoma piceae, Ophiostoma piliferum, Sphaeropsis sapinea) and decay fungi (Heterobasidion annosum, Phlebiopsis gigantea, Stereum sanguinolentum) were compared on agar medium and pine in logs at various temperatures. On agar, the growth temperature optimum of most bluestain fungi and all the decay fungi was ∼25°C, with little growth at ≤5°C or above 32.5°C. Overall, the fastest growing were S. sapinea and O. minus. In logs, the most effective colonizers were S. sapinea and O. minus with pathogenic abilities that made them well fitted to colonize the sapwood of freshly felled pine. Within these species, certain isolates produced much larger lesions in phloem and the sapwood tangential plane than all the decay fungi. Notably, there was significant variation in colonizing ability between different isolates within a species, emphasizing the need for testing a range of isolates when selecting a potential biocontrol agent.

Efficacy of Two Systemic Insecticides Injected Into Loblolly Pine for Protection Against Southern Pine Bark Beetles (Coleoptera: Curculionidae)

We evaluated the efficacy of systemic insecticides emamectin benzoate and fipronil for preventing mortality of individual loblolly pines, Pinus taeda L., as a result of attacks by southern pine bark beetles (Coleoptera: Curculionidae, Scolytinae) for two consecutive years in Mississippi (2005-2006) and Alabama (2006-2007). Trees were injected once in the spring of 2005 (Mississippi) or 2006 (Alabama) and then were baited with species-specific bark beetle lures several weeks later. The southern pine beetle, Dendroctonus frontalis Zimmermann, was the target species but was changed to Ips spp. in Mississippi (but not Alabama) the second year because of few southern pine beetle attacks on baited trees. Single injections of emamectin benzoate were effective in reducing tree mortality caused by bark beetles compared with untreated checks. Although less effective overall, fipronil also significantly reduced tree mortality from southern pine beetle compared with the checks during the second year in Alabama. Tree mortality continued well after the lures had been removed. Evaluations of bolts taken from experimental trees killed in 2006 indicated that emamectin benzoate effectively prevented parent bark beetle gallery construction and that fipronil significantly reduced lengths of galleries constructed by adult beetles, brood development, and emergence, compared with checks. In contrast, neither insecticide treatment prevented the bark beetles from inoculating blue stain fungi, Ophiostoma spp., into treated trees.

Prediction and assessment of bark beetle-induced mortality of lodgepole pine using estimates of stand vigor derived from remotely sensed data

The current outbreak of mountain pine beetle ( Dendroctonus ponderosae Hopkins) in British Columbia (BC), Canada, has led forest managers to consider thinning as a means of decreasing residual tree susceptibility to attack and subsequent mortality. Previous research indicates that susceptibility to mountain pine beetle is a function of a tree's physiological vigor and the intensity of attack. Trees able to produce ≥ 80 g (g) of wood per m 2 of projected leaf area annually are highly resistant, because they are able to shift resource allocation locally from wood to resin production to isolate blue-stain fungi introduced by attacking beetles. Typically, the leaf area of susceptible stands must be reduced by two-thirds to permit most residual trees to increase their vigor to a safe level. We evaluate whether Landsat Thematic Mapper (TM) imagery (30 × 30 m) provides a means to assess the maximum leaf area index (LAI) of unthinned stands and the extent that thinning reduces LAI. The extent that residual trees in thinned stands may have increased their resistance to attack from mountain pine beetle is predicted from a non-linear relationship between % maximum LAI and mean tree vigor. We investigated the merits of this approach in the vicinity of Parson, British Columbia using four stands of lodgepole pine ( Pinus contorta Dougl.), two of which were heavily thinned (stands were spaced to 4 and 5 m, approximately 70% reduction in stand density). An analysis of archived Landsat TM imagery indicated that prior to thinning in 1993, all four stands had full canopy, which, for mature stands, would translate to mean tree vigor between 40 and 70 g of annual wood production per m 2 of foliage. By 1995, based on estimated changes in LAI derived from a second data of Landsat TM imagery, stand vigor in the unthinned stands had not changed; however, in the thinned stands, a nearly two third reduction in LAI resulted in a predicted increase in vigor to between 100 and 160 g wood m − 2 of leaf area. A subsequent assessment in 2001 indicated that stand vigor remained higher in the thinned stands relative to the control stands. Following an infestation of mountain pine beetle in the study area in 2002, mortality data indicated that the thinned stands experienced no mortality relative to the unthinned stands which experienced 5.5% mortality in the initial years of the attack. In the larger area surrounding the study site, a general relationship was found between predicted stand vigor and mountain pine beetle-induced mortality as estimated from aerial overview survey data ( r 2 = 0.43, p < 0.01).

The efficacy of commercial silicones against blue stain and mould fungi in wood

Scots pine (Pinus sylvestris L.) samples were vacuum pressure impregnated with quaternary ammonium (quat)-silicone micro-emulsion (<40 nm particle size), amino-silicone macro-emulsion (110 nm) and silicone macro-emulsion with alkyl modified side groups (740 nm). Quat-silicone micro-emulsion caused highest cell wall bulking (4.8%) and anti-swelling efficiency (21.8%) in wood when treated with 30% concentration of silicone in the treatment solution. All three formulations made wood hydrophobic which was evident from a capillary (longitudinal, tangential and radial) water uptake test. Amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in strong resistance to blue stain attack with both pre-weathered and not pre-weathered wood samples. Signs of blue staining were more evident on the pre-weathered samples. Treatment with amino-silicone macro-emulsion (10% silicone in treatment solution) resulted in a certain resistance to mould growth on wood surfaces, whereas wood treated with the same concentration of quat-silicone micro-emulsion and alkyl-modified silicone macro-emulsion exhibited comparatively lower resistance.

Biocontrol of Blue Stain in Pine Wood with Lyophilized Mycelium of Ophiostoma quercus Albino Strain

Mycelium of Ophiostoma quercus albino strain cultured in liquid culture media was harvested, lyophilized, and stored for examining biocontrol efficacy against wood discoloration by staining fungi in the laboratory and field conditions. Dry weight of mycelium grown in brown sugar yeast extract broth(BYB) showed 3.8 times higher than that grown in potato dextrose broth(PDB). The optimum culture period in BYB was 4 weeks. In vitality test of the albino strain, the lyophilized mycelium stored in liquid nitrogen(<TEX>$-196^{\circ}C$</TEX>) or in a refrigerator(<TEX>$4^{\circ}C$</TEX>) kept the vitality until 13 months after storage; however, the mycelium stored at room temperature lost the vitality completely after 13 months. The mycelium stored in liquid nitrogen or in a refrigerator protected wood chips from the discoloration by pretreating mycelial suspension on pine wood chips. The mycelium stored at room temperature for 7 months also showed complete protection. These results suggest that the lyophilized mycelium have a biocontrol efficacy only if it keeps the least vitality. In the field conditions, both albino strain and <TEX>$Woodguard^{(R)}$</TEX>(commercial chemical protectant) showed significant differences(p=0.05) in discoloration rate as compared to the non-treated control when these were treated on the wood logs of Pinus rigida. The albino strain showed better protection than <TEX>$Woodguard^{(R)}$</TEX>. Isolation frequency of blue stain fungi from the chips of wood logs treated with the albino strain was 0% at three months after treatment, while that treated with <TEX>$Woodguard^{(R)}$</TEX> was 76.7%. In another experiment, pre-treatment of mycelial suspension on the cut surface of wood logs also showed significant protection from wood discoloration. Spraying of both albino strain on the cut surface and insecticides on the bark also showed relatively good control effects as compared to insecticide alone on the bark or nontreated control.

Variation in pathogenicity of a mountain pine beetle–associated blue-stain fungus, Grosmannia clavigera, on young lodgepole pine in British Columbia

Grosmannia clavigera is the most pathogenic blue-staining fungal associate of the mountain pine beetle (Dendroctonus ponderosae). In contrast to its importance as a primary invader of lodgepole pine (Pinus contorta) sapwood, intraspecific variability in pathogenicity of G. clavigera on lodgepole pine, the predominant host of mountain pine beetles in British Columbia, has not been investigated in detail. The present work reports on pathogenicity indicators induced by five G. clavigera isolates inoculated into lodgepole pines and growth characteristics of the isolates on artificial media. Fungi were inoculated at 200 inoculations/m2 into young lodgepole pine trees. Phloem lesion length, sapwood occlusion area, and sapwood moisture content were measured after 7 or 48 weeks. Three isolates produced long lesions, occluded larger areas, and reduced more the moisture content after 48 weeks compared with the remaining two isolates. Isolate ATCC 18086 induced the strongest pathogenic symptoms after 7 weeks and grew the fastest up to 22.5 °C but grew the slowest at 27.5 °C. In a low-oxygen environment, most isolates grew faster than under ambient conditions. Significant intraspecific variation was observed among G. clavigera isolates for all parameters tested. Key words: Grosmannia clavigera, Ophiostoma clavigerum, mountain pine beetle, blue-stain fungus, intraspecific variation, pathogenicity. Grosmannia clavigera est le plus pathogénique des champignons du bleuissement associés au dendroctone du pin ponderosa (Dendroctonus ponderosae). Contrairement à son importance en tant qu’envahisseur primaire de l’aubier du pin tordu latifolié (Pinus contorta), la variabilité intraspécifique de la pathogénicité de G. clavigera envers ce dernier, hôte principal du dendroctone du pin ponderosa en Colombie-Britannique, n’a pas été étudiée en détail. Les présents travaux font état d’indicateurs de pathogénicité produits par cinq isolats de G. clavigera appliqués sur des pins tordus latifoliés ainsi que des caractéristiques de croissance de ces isolats cultivés en milieu artificiel. De jeunes pins tordus latifoliés ont été inoculés avec le champignon à raison de 200 inoculations/m2. Au bout de 7 ou 48 semaines, la longueur des lésions subies par le phloème, la surface d’occlusion de l’aubier ainsi que son degré d’humidité ont été mesurés. Au bout de 48 semaines, comparativement aux deux autres, trois des cinq isolats avaient produit de longues lésions, occlus de plus larges surfaces et avaient davantage réduit le degré d’humidité. Au bout de 7 semaines, l’isolat ATCC 18086 avait provoqué les symptômes pathogènes les plus aigus. Son taux de croissance avait également été le plus rapide, et ce, jusqu’à 22,5 °C, pour devenir le plus lent à 27,5 °C. La plupart des isolats ont crû plus rapidement dans un environnement faible en oxygène que dans les conditions de milieu ambiant. Une variation intraspécifique significative a été observée chez les isolats de G. clavigera, et ce, relativement à tous les paramètres analysés. Mots-clés : Grosmannia clavigera, Ophiostoma clavigerum, dendroctone du pin ponderosa, champignon du bleuissement, variation intraspécifique, pathogénicité.

Antifungal effect of bark extracts from some European tree species

The inhibitory effect of methanol bark extracts from six deciduous and three coniferous European tree species were bioassayed against eight fungi from the different damage categories, brown rot, white rot, canker and blue-stain. This is the first report providing data on the antifungal activity of several Europaen tree species against fungi within these damage categories. Generally the decay fungi were more inhibited by the bark extracts than the blue-stain fungi, while the lowest inhibition was found among the cancer fungi. The main pattern found between the fungal groups in relation to the bark extracts in this study is believed to be caused by the route of ingress. Acer platanoides bark extract proved to be the most efficient bark extract tested, significantly reducing the growth rate of all tested fungi. Betula pubescens bark extract generally gave the weakest reduction in growth rate. In this study, the conifer bark extracts were in general more active against the canker and blue stain ascomycete fungi than the deciduous trees extracts.

Diffusionsverhalten von IPBC in wasserbasierten Beschichtungssystemen auf Holzfassaden

Water based coating systems for wood are more prone to infection and colonization by mould and blue stain fungi than systems with organic solvents. The addition of fungicides in coatings inhibits fungal growth on the surface and in the wood. In Europe, IPBC (3-iodo-2-propynyl butylcarbamate) is currently one of the most important fungicides used for film protection. Diffusion analysis of IPBC with HPLC showed that the primer diffused evenly into the topcoat leading to a quite homogeneous distribution. However, it only slightly penetrated (250 µm) into the wood and showed a more inhomogeneous distribution in this area. Natural weathering experiments after three months indicate that the amount of IPBC decreased to only 30% of the original content.

Biotic disturbance in expanding subarctic forests along the eastern coast of Hudson Bay

* The past and present occurrence of insect disturbance on white spruce (Picea glauca) trees was evaluated at their northern range limit on the eastern coast of Hudson Bay, and its effects on tree growth and population dynamics studied. * Three sites were sampled along an altitudinal gradient. Ring-width chronologies and stem analysis were used to evaluate tree growth. The occurrence of holes in the bark, of resin pockets and blue-stain fungi, and ring-width evidence for growth releases were used to assess the impact of bark beetle. * The white spruce population was established at these sites in the 17th century. Since their establishment, the spruce trees have developed a tree growth form, except at the uppermost site, where severe growth suppression occurred in the 19th century. Bark beetle and blue-stain fungi occurred with different timing and intensity. Their highest occurrence, associated with high mortality rates, was at the lowest site in the late 20th century. In the uppermost sites, biotic disturbance has occurred since the 18th century, associated with evidence for mechanical disturbance. * The simultaneous arrival of white spruce in the area resulted in a synchronous onset of spruce beetle activity driven by tree ageing. Unfavourable climatic conditions affected tree growth severely in the most exposed sites.

Evaluation of a mature lodgepole pine stand's resistance to the current mountain pine beetle infestation after nitrogen fertilization

Research is currently under way in the Southern Interior Forest Region to determine whether nitrogen fertilization can be used to increase mature lodgepole pine trees' natural defences against the mountain pine beetle (MPB) and thereby reduce the impact of the mpb infestation in pine stands. In fall 2006, three nitrogen fertilizer treatments (0, 200, and 400 kg N/ha) were applied randomly to each of 10 plots in a 140-year-old fire-regenerated stand of mixed lodgepole pine, spruce, and true fir. In 2007, the stand was inoculated with two isolates of blue stain fungus and with local beetle microflora. A forest health survey helped determine the level of MPB within the stand before the plot centres were baited with pheromones. Early results show that the 400 kg N/ha treatment significantly increased nitrogen levels in pine phloem and needles. No significant differences were apparent in lesion length related to nitrogen treatment levels within each of the three fungal isolates. Measurements in 2008 will show whether MPB attack success varies among nitrogen treatments.

1-Alkoxymethyl-X-dimethylaminopyridinium-base ionic liquids in wood preservation

Abstract The following pyridinium-based ionic liquids (ILs) have been successfully tested as components of potential wood preservatives: 1-alkoxymethyl-3-dimethylaminopyridinium chlorides, 1-alkoxymethyl-4-dimethylaminopyridinium chlorides, 1-alkoxymethyl-3-dimethylaminopyridinium acesulfamates and 1-alkoxymethyl-4-dimethylaminopyridinium acesulfamates. These ILs are new biocides that penetrate well into wood. The tested pyridinium ILs with an alkoxymethyl substituent, consisting of 8, 9 or 10 carbon atoms, exhibited fungicidal activity against the basidiomycetes Coniophora puteana and Trametes versicolor and the blue-stain fungus Sclerophoma pityophila. The effective and lethal doses were measured by the agar-plate method and the toxic values, before and after leaching according to EN 84, were determined based on the EN 113 block method. The doses and toxic values of tested 1-decyloxymethyl-4-dimethylaminopyridinium chloride and acesulfamate were comparable with benzalkonium chloride and didecyldimethylammonium chloride. The ILs tested were largely unleachable from wood by water. The mechanical properties of wood treated with the former two ILs were lower than natural wood. Wood treated with the chloride and acesulfamate was, however, characterized by lower absorption of free water than the control wood. Only in the case of treatment with acesulfamate was the hygroscopicity of treated wood distinctly lower than that of control wood. The durability of wood was increased by 1-decyloxymethyl-4-dimethylaminopyridinium chloride and acesulfamate.

Environmentally friendly temporary anti-mould treatment of packaging material before drying

According to FAO – ISPM No 15, in international trade wood packaging material on the basis of sawn timber requires to be heat-treated to avoid spreading of harmful organisms. “Heat-treatment” means a minimum core temperature of the wood of 56° C for a minimum of 30 minutes. ISPM No 15 does not defi ne moisture content and therefore does not include rules for the drying process. Practitioners report that fresh sapwood, after having undergone a pure heat treatment without any kind of drying, shows a great affi nity to fungi (mould and blue stain). Even though the infestation does not affect the strength properties of the wood, it must be considered as an optical and a sanitary problem. An environmentally friendly, cheap and easy to use technique for temporary anti-mould protection of heattreated wood is needed to bridge the time span between sawing, heat treatment and air or kiln drying. Results derived from laboratory experiments have shown that the heat-treatment affects the elution of the lipid components within pine sapwood. While searching for alternatives to conventional preservation methods, different environmentally compliant agents (particularly aqueous solutions containing sodiumand potassium carbonate) were found to inhibit the germination of mould and blue stain fungi spores on wood packaging material surfaces in a temporary manner. Besides their effectiveness, the usage of these agents to achieving the temporary protection (e.g. for a couple of weeks) is economically feasible and easily applicable in industrial practice. However, drying (either naturally or technically) is indispensable to avoid fungal hazard on the long run. A combination of temporary treatment immediately after sawing followed by a drying-process (long lasting protection) seems to be the most effective method to protect ISPM No 15 treated wood packaging material against mould.

Methyl jasmonate and oxalic acid treatment of Norway spruce: anatomically based defense responses and increased resistance against fungal infection

To study the effect of chemical pretreatment on conifer resistance, 13-year-old Norway spruce (Picea abies (L.) Karst.) trees were treated with methyl jasmonate (MJ) or oxalic acid (OxA) on the outer bark and inoculated with the pathogenic blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau 4 weeks later. Both chemicals significantly reduced symptoms of fungal infection, but MJ was more effective than OxA (51 versus 18% reduction in length of necrotic lesions in the phloem relative to untreated control trees). Anatomical examination of treated stem tissues showed that MJ induced extensive formation of traumatic resin ducts in the xylem and extra polyphenolic parenchyma (PP) cells in the secondary phloem between the cambium and the regular annual PP cell layer. No traumatic resin ducts were formed after treatment with OxA, and the coverage of extra PP cells in OxA-treated tissues was not significantly higher than in the controls. The anatomically based defense reactions induced by MJ were similar to the reactions observed after pathogen infection, mechanical wounding and bark beetle attack. Neither MJ nor OxA had apparent phytotoxic effects on Norway spruce at the concentrations used, with needle and stem tissues of all trees appearing normal without visible symptoms of toxicity. However, trees treated with MJ had 30% less radial sapwood growth than control trees. In conclusion, MJ treatment of Norway spruce appears to have practical potential as a tool for increasing plant resistance to fungal infection, but with a modest reduction in sapwood growth.

Spatial and Temporal Dynamics of Bark Beetles in Chinese White Pine in Qinling Mountains of Shaanxi Province, China

Spatial and temporal dynamics of bark beetles in single tree trunks of Pinus armandi were studied in Qinling Mountains, Shaanxi Province, China. Ten species of engraver bark beetles attacked from healthy to withered Chinese white pines, but seven species were commonly detected every year in Qinling forest ecosystem. Dendroctonus armandi and Hylurgops longipilis were common species at the lower of trunks, and Ips acuminatus, Polygraphus sinensis, and Pityogenes japonicus primary distributed in the middle of trunks, whereas population densities of Cryphalus lipingensis and C. chinlingensis centralized at the upper trunks and branches of Chinese white pines. On the time series, D. armandi, as a dominant species in Chinese white pines of Qinling forest ecosystem, mainly attacked healthy and weakened trees and cooperated with blue stain fungus that resulted in the declining abruptly resistance and triggered the secondary bark beetles to attack the infected or withered host trees. Attacking and colonizing phenology of bark beetles in Qinling forest ecosystem are caused by complex interactions among spatial and trophic competition and cooperation and exhibit particular spatial and temporal patterns. Our results support the view that competition and cooperation within bark beetles are a critical factor to influence bark beetles spatial and temporal distribution, and stability of bark beetles’ ecosystem, D. armandi, I. acuminatus, P. japonicus, P. sinensis, C. lipingensis, C. chinlingensis, and H. longipilis in Chinese white pine of Qinling forest ecosystem.