Primary attraction and kairomonal host discrimination in three species of Dendroctonus (Coleoptera: Scolytidae)

Abstract 1 Synthetic blends of bole and foliage volatiles of four sympatric species of conifers were released from pheromone‐baited multiple‐funnel traps to determine if three species of tree‐killing bark beetles (Coleoptera: Scolytidae): (i) exhibited primary attraction to volatiles of their hosts and (ii) discriminated among volatiles of four sympatric species of host and nonhost conifers. 2 Bole and foliage volatiles from Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco, increased the attraction of coastal and interior Douglas‐fir beetles, Dendroctonus pseudotsugae Hopkins, to pheromone‐baited traps. Primary attraction to bole volatiles was observed in interior D. pseudotsugae. Beetles were significantly less attracted to the pheromone bait when it was combined with volatiles of lodgepole pine, Pinus contorta var. latifolia Engelm. or interior fir, Abies lasiocarpa × bifolia. 3 The monoterpene myrcene synergized attraction of mountain pine beetles, Dendroctonus ponderosae Hopkins, to their aggregation pheromones, but there was no evidence of primary attraction to host volatiles or discrimination among volatiles from the four conifers. 4 There was significant primary attraction of the spruce beetle, Dendroctonus rufipennis Kirby, to bole and foliage volatiles of interior spruce, Picea engelmannii × glauca, but beetles did not discriminate among volatiles of four sympatric conifers when they were combined with pheromone baits. 5 Our results indicate that host volatiles act as kairomones to aid pioneer Douglas‐fir beetles and spruce beetles in host location by primary attraction, and that their role as synergists to aggregation pheromones is significant. For the mountain pine beetle, we conclude that random landing and close range acceptance or rejection of potential hosts would occur in the absence of aggregation pheromones emanating from a tree under attack.     

Dwarf mistletoe affects whole-tree water relations of Douglas fir and western larch primarily through changes in leaf to sapwood ratios

Dwarf mistletoes induce abnormal growth patterns and extreme changes in the biomass allocation of their hosts as well as directly parasitizing them for resources. Because biomass allocation can affect the resource use and efficiency of conifers, we studied the influences of dwarf mistletoe infection on above-ground biomass allocation of Douglas fir and western larch, and the consequences of such changes on whole-tree water use and water relations. Sap flow, tree water potentials, leaf:sapwood area ratios (A_L:A_S), leaf carbon isotope ratios, and nitrogen content were measured on Douglas fir and western larch trees with various degrees of mistletoe infection during the summer of 1996 in western Montana. Heavy dwarf mistletoe infection on Douglas fir and western larch was related to significant increases in A_L:A_S. Correspondingly, water transport dynamics were altered in infected trees, but responses were different for the two species. Higher A_L:A_S ratios in heavily infected Douglas firs were offset by increases in sapwood area-based sap flux densities (Q_SW) such that leaf area-based sap flux densities (Q_L) and predawn leaf water potentials at the end of the summer did not change significantly with mistletoe infection. Small (but statistically insignificant) decreases of Q_L for heavily infected Douglas firs were enough to offset increases in leaf area such that whole-tree water use was similar for uninfected and heavily infected trees. Increased A_L:A_S ratios of heavily infected western larch were not offset by increases of Q_SW. Consequently, Q_L was reduced, which corresponded with significant decreases of water potential at the end of the summer. Furthermore, mistletoe-infection-related changes in A_L:A_S as a function of tree size resulted in greater whole-tree water use for large infected larches than for large uninfected trees. Such changes may result in further depletion of limited soil water resources in mature infected stands late in the growing season. Foliage from infected trees of both species had lower water use efficiencies than non-infected trees. Our results demonstrate substantial changes of whole-tree processes related to mistletoe infection, and stress the importance of integrating whole-tree physiological and structural processes to fully understand the mechanisms by which pathogens suppress forest productivity.     

Host resistance in defoliated pine: effects of single and mass inoculations using bark beetle-associated blue-stain fungi

1 In 1996, 7000 ha of pine forests were defoliated by the pine looper Bupalus piniaria in south‐western Sweden. 2 The susceptibility of trees of different defoliation classes (0, 30, 60, 90 and 100% defoliation) to beetle‐vectored blue‐stain fungi was tested in inoculation experiments. Forty and 120‐year‐old Scots pine trees were inoculated with ‘single’, i.e. a few inoculations of Leptographium wingfieldii and Ophiostoma minus, two blue‐stain fungi associated with the pine shoot beetle Tomicus piniperda. The young trees were also ‘mass’ inoculated with L. wingfieldii at a density of 400 inoculation points per m² over a 60 cm stem belt. 3 Host tree symptoms indicated that only trees with 90–100% defoliation were susceptible to the mass inoculation. 4 Single inoculations did not result in any consistent differences in fungal performance between trees of different defoliation classes, regardless of inoculated species or tree age class. 5 Leptographium wingfieldii produced larger reaction zones than O. minus, and both species produced larger lesions in old than in young trees. 6 As beetle‐induced tree mortality in the study area occurred only in totally defoliated stands, mass inoculations seem to mimic beetle‐attacks fairly well, and thus seem to be a useful tool for assessing host resistance. 7 As even severely defoliated pine trees were quite resistant, host defence reactions in Scots pine seem to be less dependent on carbon allocation than predicted by carbon‐based defence hypotheses.     

Aphid-induced reduction of shoot and root growth in Douglas-fir seedlings

1. The short‐ and long‐term effects of photosynthate removal by sap‐sucking herbivores on plant growth were examined by experimentally manipulating densities of an aphid Cinara pseudotsugae (Wilson) on 2‐year‐old Douglas‐fir seedlings Pseudotsuga menziesii (Mirb.) Franco under greenhouse conditions. An 18‐week test was conducted to determine short‐term effects. Effects of long‐term aphid feeding were examined by exposing seedlings to aphid feeding for two consecutive growing seasons. A third experiment evaluated the extent of recovery during 1 year following a single season of aphid feeding. At least 35 seedlings were used in each test. 2. Volume and dry weight of both shoots and roots decreased significantly with increasing aphid feeding in all three experiments. 3. The most significant and severe aphid effect was reduced root tissue density, suggesting carbohydrate depletion due to translocation from roots to shoots. 4. There was no sign of recovery, of either root or shoot growth, during the year following one season of feeding. 5. The results of this study indicate that short‐term feeding by aphids can affect plant growth and structure for a relatively long time.     

Tree‐ring stable isotopes record the impact of a foliar fungal pathogen on CO2 assimilation and growth in Douglas‐fir

Swiss needle cast (SNC) is a fungal disease of Douglas‐fir (Pseudotsuga menziesii) that has recently become prevalent in coastal areas of the Pacific Northwest. We used growth measurements and stable isotopes of carbon and oxygen in tree‐rings of Douglas‐fir and a non‐susceptible reference species (western hemlock, Tsuga heterophylla) to evaluate their use as proxies for variation in past SNC infection, particularly in relation to potential explanatory climate factors. We sampled trees from an Oregon site where a fungicide trial took place from 1996 to 2000, which enabled the comparison of stable isotope values between trees with and without disease. Carbon stable isotope discrimination (Δ¹³C) of treated Douglas‐fir tree‐rings was greater than that of untreated Douglas‐fir tree‐rings during the fungicide treatment period. Both annual growth and tree‐ring Δ¹³C increased with treatment such that treated Douglas‐fir had values similar to co‐occurring western hemlock during the treatment period. There was no difference in the tree‐ring oxygen stable isotope ratio between treated and untreated Douglas‐fir. Tree‐ring Δ¹³C of diseased Douglas‐fir was negatively correlated with relative humidity during the two previous summers, consistent with increased leaf colonization by SNC under high humidity conditions that leads to greater disease severity in following years.     

Ophiostomatoid fungi associated withIps cembrae in Japan and their pathogenicity of Japanese larch

Six ophiostomatoid fungi, i.e.,Ceratocystiopsis minuta, Ceratocystis laricicola, Ophiostoma brunneo-ciliatum, O. laricis, O. piceae andOphiostoma sp., were isolated from the galleries ofIps cembrae on Japanese Iarch (Larix kaempferi) logs in central Honshu, Japan. Japanese larch trees approximately 30 yr old were inoculated with all six fungi.Ceratocystis laricicola produced the largest lesions on the inner bark around the inoculation point and the largest dry zone in the sapwood. Furthermore,C. laricicola was the only fungus associated withI. cembrae that had the ability to kill Japanese larch, death occurring in 30-yr-old trees within 3.5 mo after inoculation.     

Large Shift in Symbiont Assemblage in the Invasive Red Turpentine Beetle

Changes in symbiont assemblages can affect the success and impact of invasive species, and may provide knowledge regarding the invasion histories of their vectors. Bark beetle symbioses are ideal systems to study changes in symbiont assemblages resulting from invasions. The red turpentine beetle (Dendroctonus valens) is a bark beetle species that recently invaded China from its native range in North America. It is associated with ophiostomatalean fungi in both locations, although the fungi have previously been well-surveyed only in China. We surveyed the ophiostomatalean fungi associated with D. valens in eastern and western North America, and identified the fungal species using multi-gene phylogenies. From the 307 collected isolates (147 in eastern North America and 160 in western North America), we identified 20 species: 11 in eastern North America and 13 in western North America. Four species were shared between eastern North America and western North America, one species (Ophiostoma floccosum) was shared between western North America and China, and three species (Grosmannia koreana, Leptographium procerum, and Ophiostoma abietinum) were shared between eastern North America and China. Ophiostoma floccosum and O. abietinum have worldwide distributions, and were rarely isolated from D. valens. However, G. koreana and L. procerum are primarily limited to Asia and North America respectively. Leptographium procerum, which is thought to be native to North America, represented >45% of the symbionts of D. valens in eastern North America and China, suggesting D. valens may have been introduced to China from eastern North America. These results are surprising, as previous population genetics studies on D. valens based on the cytochrome oxidase I gene have suggested that the insect was introduced into China from western North America.     

Ophiostomatoid fungi associated with the northern spruce engraver, <Emphasis Type="Italic">Ips perturbatus</Emphasis>, in western Canada

A number of ophiostomatoid fungi were isolated from the spruce-infesting bark beetle, Ips perturbatus and its galleries collected from felled spruce trees and logs in northern BC and the Yukon Territory. Isolates were identified to species using morphological characteristics, nuclear ribosomal DNA and partial β-tubulin gene sequences. Thirteen morphological and phylogenetic species were identified among the isolates. Leptographium fruticetum, Leptographium abietinum, Ophiostoma bicolor, Ophiostoma manitobense, O. piceaperdum, and eight undescribed species of the genus Ophiostoma and the anamorph genera Leptographium, Hyalorhinocladiella, Ambrosiella and Graphium. A number of these species, i.e. L. fruticetum, Hyalorhinocladiella sp. 2, O. bicolor and O. manitobense, were isolated repeatedly from I. perturbatus, while others, i.e. Graphium sp. 1 and O. piceaperdum, seemed to be␣sporadic associates. Among all the isolates, L. fruticetum had the highest relative dominance in this survey. A high frequency of occurrence of this species with the beetle may indicate a specific relationship between the two partners.     

Colour of larch heartwood and relationships to extractives and brown-rot decay resistance

Larch heartwood is appreciated for its good mechanical properties, its colour and its texture, and it is often used outdoors because of its natural durability (decay resistance). In this study the colour of larch heartwood was studied in relation to extractives and decay resistance, with the aim to estimate durability of larch heartwood from its colour. On a total of 293 trees colour in the CIE L*a*b* space (L* lightness, a* red/green axis, b* yellow/blue axis), extractives content (acetone and hot-water extractives, amount of phenolics) and the brown-rot decay resistance were determined. For calculating the relative decay resistance ( x), mass loss after inoculation for 16 weeks with two fungi [ Coniophora puteana (Schum.ex.Fr.) Karst., Poria placenta (Fr.) Cke, European standard EN 113] of larch heartwood samples was compared to Scots pine ( Pinus sylvestris L) sapwood reference samples (EN 350-1). Different species [Japanese larch ( Larix kaempferi Lamb.), Hybrid larch (Larix deciduax L. kaempferi) and European larch ( L. decidua Mill.)], provenances and age classes (38-year, >150-year) were included. Japanese larch heartwood turned out to be significantly more reddish (higher a*-values) compared to the European larch provenances. Reddishness of the hybrids was intermediate. The red hue (+a*) was strongly correlated with the amount of phenols ( r =0.84) and decay resistance ( r =0.63) and therefore suitable for prediction of both parameters. The results suggest that colour measurements of larch heartwood could be of benefit in tree breeding programs and for an optimised utilization of larch timber.     

Strong indirect interactions of Tarsonemus mites (Acarina: Tarsonemidae) and Dendroctonus frontalis (Coleoptera: Scolytidae)

Phoretic mites of bark beetles are classic examples of commensal ectosymbionts. However, many such mites appear to have mutualisms with fungi that could themselves interact with beetles. We tested for indirect effects of phoretic mites on Dendroctonus frontalis, which attacks and kills pine trees in North America. Tarsonemus mites are known to carry ascospores of Ophiostoma minus, which tends to outcompete the mutualistic fungi carried by D. frontalis. Experimental additions and removals of mites from beetles demonstrated that Tarsonemus propagate O. minus in beetle oviposition galleries. Furthermore, the abundance of Tarsonemus and O. minus tended to covary in nature. These results verified a strong mutualism between Tarsonemus and O. minus. Results also indicated that O. minus is an antagonist of D. frontalis: beetle larvae seldom survived in the presence of O. minus (compared to 83% survival elsewhere). Apparently, this is an indirect result of O. minus outcompeting the two species of mycangial fungi that are critical to beetle nutrition. Thus, Tarsonemus mites close a loop of species interactions that includes a commensalism (mites and beetles), a mutualism (mites and O. minus), asymmetric competition (O. minus and mycangial fungi), and another mutualism (mycangial fungi and beetles). This interaction system produces negative feedback that could contribute to the endogenous population dynamics of D. frontalis. Reproductive rate of Tarsonemus was more temperature‐sensitive than beetle generation time (which constrains the time for mite reproduction within a tree). This differential temperature sensitivity produces a narrow range of temperatures (centred at 27°C) in which mite reproduction per D. frontalis generation can attain its maximum of 100 mites/beetle. Consequently, seasonal oscillations in temperature are predicted to produce oscillations in the D. frontalis community, and climatic differences between regions could influence the community to dampen or exacerbate the cyclical outbreak dynamics of D. frontalis.     

Climate-related trends in sapwood biophysical properties in two conifers: avoidance of hydraulic dysfunction through coordinated adjustments in xylem efficiency, safety and capacitance

In the Pacific north‐west, the Cascade Mountain Range blocks much of the precipitation and maritime influence of the Pacific Ocean, resulting in distinct climates east and west of the mountains. The current study aimed to investigate relationships between water storage and transport properties in populations of Douglas‐fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) adapted to both climates. Sapwood thickness, capacitance, vulnerability to embolism, and axial and radial conductivity were measured on samples collected from trunks of mature trees. The sapwood of ponderosa pine was three to four times thicker than Douglas‐fir. Radial conductivity was higher in west‐side populations of both species, but axial conductivity was higher in the east‐side populations and in Douglas‐fir. Eastern populations of both species had sapwood that was more vulnerable to embolism than west‐side populations. Sapwood capacitance was similar between species, but was about twice as great in east‐side populations (580 kg m^?3 MPa^?1) as in west‐side populations (274 kg m^?3 MPa^?1). Capacitance was positively correlated with both mean embolism pressure and axial conductivity across species and populations, suggesting that coordinated adjustments in xylem efficiency, safety and water storage capacity may serve to avoid embolism along a gradient of increasing aridity.     

Resin and the Resistance of Conifers to Fomes annosus

Roots of young trees of different conifer species, Scots pine,Corsican pine, Sitka spruce, and Douglas fir were inoculatedwith Fomes annosus. In the pines, infection was negligible butin the other genera the central wood was extensively invaded.The process of infection was studied further in Sitka spruceby means of a root-severing technique in which an inoculum blockwas forced between the cut ends of a root. In most trees a centralrot developed which in some extended up into the butt: the meanextent of growth recorded was 30 cm in 14 months. In the severedroot portions infection also occurred but F. annosus was subsequentlyreplaced to a considerable extent by other micro-organisms,particularly in trees growing on a peat soil. A similar centralrot developed after inoculations of Norway spruce. The resistance of pine sapwood and the outer wood of spruceand Douglas fir can be explained at least partially by the structureand viability of the resin duct system. Larch, Douglas fir,spruce, and pine form a series showing increasing complexityand activity of the resin system. In addition, studies carriedout on the resin yields of pines growing under different conditionsshowed that the resistance of a tree to F. annosus is correlatedwith its ability to mobilize resin. Site factors, forest management,host age vigour, genetic constitution, and past history mayall influence resin mobilization.     

Constant association of ophiostomatoid fungi with the bark beetle <Emphasis Type="Italic">Ips subelongatus</Emphasis> invading Japanese larch logs

Ceratocystiopsis, Ceratocystis, Grosmannia, and Ophiostoma species were isolated from Ips subelongatus and beetle-infested Japanese larch logs collected at several areas in central and northern Honshu Island, Japan, to determine constant associates of I. subelongatus. Ceratocystiopsis minuta, two species of Ceratocystis, three species of Grosmannia, and four species of Ophiostoma were isolated. Of the fungi isolated in the present study, G. laricis, O. brunneociliatum, and O. piceae were constant associates of the beetles. Ceratocystis fujiensis, Ceratocystiopsis minuta, and Ophiostoma sp. F were occasionally isolated with high frequencies of occurrence but were not consistent associates. Ceratocystis fujiensis was most often isolated as the leading fungal invasion in the sapwood of Japanese larch logs invaded by I. subelongatus, confirming that the fungus acts as a primary invader of sapwood in beetle-attacked logs. Contribution No. 221, Laboratory of Plant Parasitic Mycology, Graduate School of Life and Environmental Sciences, University of Tsukuba     

Effect of associated fungi on the immunocompetence of red turpentine beetle larvae,Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae)

Abstract Dendroctonus–fungus symbioses are often considered as the ideal model systems to study the development and maintenance of ectosymbioses, and diverse interactions, including antagonism, commensalism and mutualism, have been documented between these organisms. The red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Curculionidae: Scolytinae) is a pine‐killing invasive beetle in northern China. Fungi species Ophiostoma minus, Leptographium sinoprocerum, L. terebrantis and L. procerum were associated with this bark beetle. Antagonistic interactions between D. valens and its associated fungi, such as O. minus and L. sinoprocerum, have been demonstrated, but the underlying causes of this phenomenon are unknown. Here, we first found the two tested fungi species retarded the net weight gain of D. valens larvae after completing 3‐day feeding on their media. Furthermore, we provide direct evidence indicating the effect of associated fungi on the immunocompetence of D. valens larvae to explain the documented antagonism. Our results showed that the activity of phenoloxidase and total phenoloxidase in D. valens larvae were significantly upregulated by two strains of associated fungi, O. minus and L. sinoprocerum as compared with the controls. The phenoloxidase ratio increased significantly in the larvae which had fed for 3 days on media inoculated with O. minus. Because insect immune defenses are costly to be deployed, these results could be explored as one of the underlying mechanisms of the documented antagonism.     

Evidence for multiple ecological roles of Leptographium abietinum,a symbiotic fungus associated with the North American spruce beetle

The ophiostomatoid fungus Leptographium abietinum is symbiotic with the North American spruce beetle Dendroctonus rufipennis; however, the ecology of these interactions are not understood. Multiple functional hypotheses regarding beetle-symbiont interactions pervade the literature, especially the view that symbionts may provide nutrition, competitively exclude antagonistic microbes, or detoxify host plant compounds. Here, these three hypotheses are tested in an effort to discern whether the ecological profile of L. abietinum is consistent with bark beetle-fungus mutualisms. Three important findings emerged: (1) by comparison with conifer phloem, L. abietinum mycelia contained considerable quantities of N, P, and protein; (2) L. abietinum outcompetes a ubiquitous entomopathogen for growing space in a resource-limited environment and can maintain captured space; and (3) inoculation with L. abietinum significantly reduced concentrations of a tree defensive compound, (+)-3-carene, in growth media. Collectively, these findings indicate that L. abietinum fulfills multiple ecological functions that are potentially consistent with bark beetle-fungus mutualism.     

Carabid beetles (Coleoptera: Carabidae) in coniferous plantations in Hokkaido,Japan: effects of tree species and environmental factors

The distribution, species composition and abundance of carabid beetles in monospecific plantations of three different coniferous tree species (Japanese spruce, Sakhalin fir and larch) were investigated by baited pitfall traps in Hokkaido, Japan. In total, 16 150 carabid beetles consisting of 31 species in 13 genera were collected in 2011 and 2012. The most predominant species was Pterostichus thunbergii Morawitz, followed by Synuchus melantho (Bates) and Carabus opaculus (Putzeys). Average numbers of beetles per trap were significantly reduced in larch. Large‐sized Carabus species (C. arboreus arboreus Lewis and C. opaculus) were collected in large numbers in Japanese spruce. There was no significant difference in diversity and equitability among the three kinds of plantation. The ordination of redundancy analysis showed that medium‐sized forest generalists, Pterosticus subovatus (Motschulsky) and P. thunbergii, were highly associated with Japanese spruce and Sakhalin fir, and the forest specialist Synuchus nitidus (Motschulsky) was with Sakhalin fir. In contrast, in larch there was no such associated forest species, and some species of Carabus, Pterostichus and Synuchus were considerably reduced in number, suggesting that larch has unfavorable effects on some forest species. The most important environmental variables influencing carabid assemblages were soil moisture and foliage layer cover. Practices in forest management to minimize the effects of plantations on carabid assemblages are discussed.     

What explains landscape patterns of tree mortality caused by bark beetle outbreaks in Greater Yellowstone?

Aim Bark beetle outbreaks have recently affected extensive areas of western North American forests, and factors explaining landscape patterns of tree mortality are poorly understood. The objective of this study was to determine the relative importance of stand structure, topography, soil characteristics, landscape context (the characteristics of the landscape surrounding the focal stand) and beetle pressure (the abundance of local beetle population eruptions around the focal stand a few years before the outbreak) to explain landscape patterns of tree mortality during outbreaks of three species: the mountain pine beetle, which attacks lodgepole pine and whitebark pine; the spruce beetle, which feeds on Engelmann spruce; and the Douglas‐fir beetle, which attacks Douglas‐fir. A second objective was to identify common variables that explain tree mortality among beetle–tree host pairings during outbreaks. Location Greater Yellowstone ecosystem, Wyoming, USA. Methods We used field surveys to quantify stand structure, soil characteristics and topography at the plot level in susceptible stands of each forest type showing different severities of infestation (0–98% mortality; n= 129 plots). We then used forest cover and beetle infestation maps derived from remote sensing to develop landscape context and beetle pressure metrics at different spatial scales. Plot‐level and landscape‐level variables were used to explain outbreak severity. Results Engelmann spruce and Douglas‐fir mortality were best predicted using landscape‐level variables alone. Lodgepole pine mortality was best predicted by both landscape‐level and plot‐level variables. Whitebark pine mortality was best – although poorly – predicted by plot‐level variables. Models including landscape context and beetle pressure were much better at predicting outbreak severity than models that only included plot‐level measures, except for whitebark pine. Main conclusions Landscape‐level variables, particularly beetle pressure, were the most consistent predictors of subsequent outbreak severity within susceptible stands of all four host species. These results may help forest managers identify vulnerable locations during ongoing outbreaks.     

The possibility of using cyanobacterial bloom materials as a medium for white rot fungi

Aims: The present study was conducted to evaluate the possibility of using cyanobacterial bloom materials as a medium for white rot fungi and the capability of white rot fungi, Trichaptum abietinum 1302BG and Lopharia spadicea to biodegrade dried cyanobacterial bloom material taken from Taihu Lake. Methods and Results: The results showed T. abietinum 1302BG and L. spadicea could use the cyanobacterial bloom materials taken from Taihu Lake for growth to measure the mycelial plaque and dry‐weight mycelial pellicles of fungi. The removal rate of dried cyanobacterial bloom materials incubated with white rot fungi is approximately 100%. Conclusions: The cyanobacterial bloom material can be used as a glucose substitute in white rot fungi medium. The white rot fungi, T. abietinum 1302BG and L. spadicea, can also directly decrease the biomass of cyanobacterial bloom material taken from Taihu Lake. Significance and Impact of the Study: Cyanobacterial bloom thrives in eutrophic fresh waters all over the world. Micro‐organisms, particularly fungi, have attracted attention as possible agents for the degradation of phytoplankton species. Dealing with cyanobacterial bloom material as a medium for fungi instead of directly discharging them as organic fertilizers is a new, safe and environmentally friendly approach.     

Non-pesticide alternatives for reducing feeding damage caused by the large pine weevil (Hylobius abietis L.)

The large pine weevil (Hylobius abietis L.) is an important pest of young forest stands in Europe. Larvae develop under the bark of freshly cut pine and spruce stumps, but maturing weevils feed on the bark of coniferous seedlings. Such seedlings frequently die because of bark consumption near the root collar. We tested the effect of three treatments (the insecticide alpha cypermethrin, a wax coating and a glue coating) on the feeding damage caused by H. abietis on Douglas fir (Pseudotsuga menziesii) and Norway spruce (Picea abies) seedlings under semi-natural conditions. In two experiments (one in 2016 and another in 2017) seedlings in cages were subjected to pine weevil feeding for 16 weeks under shaded outdoor conditions. The experiment in 2016 compared insecticide and wax treatments and an untreated control on Douglas fir and Norway spruce, and the experiment in 2017 compared insecticide, wax and glue treatments and an untreated control on Norway spruce. In both experiments, all treatments significantly reduced H. abietis feeding damage at week 8 at the end of both experiments (week 16); the effect of treatments was significant only on spruce seedlings. The damages on Douglas fir seedlings was less on treated seedlings than on untreated control seedlings but differences were not significant. Coating stems with glue and especially with wax was generally effective at reducing weevil damage and in most cases provided control that was not significantly different from that provided by insecticide treatment. Our results suggest that a wax coating has the potential to replace the protection of seedlings provided by insecticides.     

The impact of host plant species on the larval development of the large pine weevil Hylobius abietis L.

• 1 The developmental performance of the large pine weevil Hylobius abietis was studied in the laboratory on four species of conifer, Corsican pine Pinus nigra var. maritima, Sitka spruce Picea sitchensis, Douglas‐fir Pseudotsuga menziesii and Japanese larch Larix kaempferi.
• 2 All species supported development, but, there was considerable variation in larval mortality, development time and weight of adults on emergence between host species.
• 3 Levels of mortality were highest in Japanese larch (77%) and lowest in Corsican pine (8.2%), and the heaviest adults emerged from Corsican pine (130 mg) and the smallest from Douglas‐fir (74 mg).
• 4 A constitutive plant defence chemical, lignin, found to vary within a northern provenance of Sitka spruce, also strongly affected larval development.
• 5 The significance of these findings is discussed in relation to the management of H. abietis.