Incidence of bark- and wood-boring insects in firewood: a survey at Michigan's Mackinac Bridge

Firewood is a major pathway for the inadvertent movement of bark- and wood-infesting insects. After discovery of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in southeastern Michigan in 2002, quarantines were enacted including prohibition of transporting firewood across the Mackinac Bridge between Michigan's Lower and Upper peninsulas. Drivers are required to surrender firewood before crossing the bridge. We surveyed recently surrendered firewood in April, July, and September 2008 and categorized it by genus, cross-sectional shape (whole, half, or quarter), approximate age (years since it was a live tree), presence of bark, and evidence of bark- and wood-boring insects. The 1045 pieces of firewood examined represented 21 tree genera: primarily Acer (30%), Quercus (18%), Fraxinus (15%), Ulmus (12%), Betula (5%), and Prunus (5%). Live borers (Bostrichoidea, Brentidae, Buprestidae, Cerambycidae, Cossidae, Curculionidae [Scolytinae and non-Scolytinae], and Siricidae) were found in 23% of the pieces and another 41% had evidence of previous borer infestation. Of the 152 Fraxinus firewood pieces, 13% had evidence of past A. planipennis infestation, but we found no live A. planipennis. We discuss national "don't move firewood" campaigns and U.S. imports of fuelwood. During 1996-2009, the United States imported fuelwood valued at > dollars U.S. 98 million from 34 countries.     

Effect of deadwood management on saproxylic beetle richness in the floodplain forests of northern Italy: some measures for deadwood sustainable use

Saproxylic beetles may act as bio-indicators of high-quality mature woodlands, and their conservation is strongly linked to the quality and quantity of deadwood in a biotope. We tested the effect of deadwood accumulation and habitat variables on saproxylic species richness by investigating six sampling sites under different deadwood management practices that belong to both alluvial and riparian mixed forests of the Po plain, Italy. We sampled 43 obligate saproxylic species. The main factor predicting saproxylic species richness was the amount of deadwood measured by both log diameter and volume. We found a threshold of 0.22 m diameter (confidence interval CI 0.18–0.37 m) and 32.04 m³/ha volume (CI 16.09–64.09 m³/ha) below which saproxylic beetle richness would be significantly reduced and a threshold of 35 m³/ha dead wood volume (CI 33–40 m³/ha) over which species richness increases by <5 %. The other deadwood and environmental components influenced saproxylic beetle richness to a lesser extent; some of them, however, should still be considered for proper management. Forest structure variables describing forest density such as large trees and basal areas have a negative effect on species richness. According to the results of our study, stumps and advanced decaying class are positively correlated, while small logs are negatively correlated to species richness. Thus, in extensively managed forests, the regular cutting of trees should be implemented to create artificial stumps, in order to assure a continuity of deadwood and, in the meantime, increase the number and width of openings in the forest. Moreover, prolonging rotation times can assure the presence of deadwood at intermediate/later stages of decay.     

Impacts of silvicultural thinning treatments on beetle trap captures and tree attacks during low bark beetle populations in ponderosa pine forests of northern Arizona

Our research used a combination of passive traps, funnel traps with lures, baited trees, and surveys of long-term thinning plots to assess the impacts of different levels of stand basal area (BA) on bark beetle tree attack and on trap captures of Ips spp., Dendroctonus spp., and their predators. The study occurred at two sites in ponderosa pine, Pinus ponderosa Dougl. ex Laws., forests, from 2004 to 2007 during low bark beetle populations. Residual stand BA ranged from 9.0 to 37.0 m2/ha. More predators and bark beetles were collected in passive traps in stands of lower BA than in stands of higher BA; however, significance varied by species and site, and total number of beetles collected was low. Height of the clear panel passive traps affected trap catches for some species at some sites and years. When pheromone lures were used with funnel traps [Ips pini (Say) lure: lanierone, +03/-97 ipsdienol], we found no significant difference in trap catches among basal area treatments for bark beetles and their predators. Similarly, when trees were baited (Dendroctonus brevicomis LeConte lure: myrcene, exo-brevicomin and frontalin), we found no significant difference for days to first bark beetle attack. Surveys of long-term thinning treatments found evidence of bark beetle attacks only in unthinned plots (approximately 37 m2/ha basal area). We discuss our results in terms of management implications for bark beetle trapping and control.     

Glacial survival and local adaptation in an alpine leaf beetle

The challenge in defining conservation units so that they represent evolutionary entities has been to combine both genetic properties and ecological significance. Here we make use of the complexity of the European Alps, with their genetic landscape shaped by geographical barriers and postglacial colonization, to examine the correlation between ecological and genetic divergence. Montane species, because of the fragmentation of their present habitat, constitute extreme cases in which to test if genetically distinct subgroups based on neutral markers are also ecologically differentiated and show local adaptation. In the leaf beetle Oreina elongata, populations show variation in host plant use and a patchy distribution throughout the Alps and Apennines. We demonstrate that despite very strong genetic isolation (F(ST) = 0.381), variation in host plant use has led to differences in larval life-history traits between populations only as a secondary effect of host defence chemistry, and not through physiological adaptation to plant nutritional value. We also establish that populations that are more ecologically different in terms of larval performance are also more genetically divergent. In addition, morphological variation used to define subspecies appears to be mirrored in the population genetics of this species, resulting in almost perfect clustering based on microsatellite data. Finally, we argue from their strong genetic structure and congruent distribution that the subspecies of O. elongata were divided among the same glacial refugia within the Alps that have been proposed for alpine plants.     

First record of the family Bothrideridae (Coleoptera) in Korea represented by the wood-boring beetle ectoparasite,Dastarcus helophoroides

The ectoparasitic beetle, Dastarcus helophoroides (Fairmaire), was observed for the first time in Korea as a result of a study of the natural enemies of Monochamus alternatus Hope and M. saltuarius Gebler, the vector of the pine wood nematode (Bursaphelenchus xylophilus (Steiner & Buhner)). Diagnostic illustrations are provided and the biology and host range of D. helophoroides (Fairmaire) are reviewed.     

Induced terpene accumulation in Norway spruce inhibits bark beetle colonization in a dose-dependent manner

Background

Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization.

Methods

To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark.

Results

Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m⁻²) and 2.6% as much gallery length (0.029 m m⁻² vs. 1.11 m m⁻²) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of ∼100 mg terpene g⁻¹ dry phloem trees suffered only moderate beetle colonization, and above a high threshold of ∼200 mg terpene g⁻¹ dry phloem trees were virtually unattacked.

Conclusion/Significance

This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.     

Enhancing carrot somatic embryos survival during slow dehydration, by encapsulation and control of dehydration

In order to obtain dry artificial seeds, carrot somatic embryos were encapsulated and dehydrated. Encapsulation in some hydrogels delayed the dehydration and preserved the water content of carrot somatic embryos. In particular, a matrix made of alginate with gellan gum was found to be the most efficient in maintaining a high water activity (a_w) around somatic embryos. By delaying dehydration, and also rehydration, encapsulation seemed to protect somatic embryos against desiccation and imbibition damages, giving better germination and emergence of cotyledons. Matrices made of alginate mixed with kaolin or gellan gum were particularly adapted to protect the embryos during the dehydration. Apart from the matrix composition, the control of dehydration speed enhanced the survival and regeneration of encapsulated-dehydrated somatic embryos. Using a slow dehydration protocol (95-15% RH—relative humidity into the chamber—in 11.5 days), it was possible to exert different dehydration speeds. Slowing the dehydration between 70 and 45% RH stabilized the water activity (a_w) of the encapsulation matrix, and enhanced the survival and regeneration frequencies of encapsulated-dehydrated embryos. In the absence of any maturing pretreatment, alginate-gellan gum encapsulated carrot somatic embryos, dehydrated to 15% RH, and rehydrated in moistured air (90% RH), germinated up to 72.9%. Therefore, encapsulation in alginate-gellan gum, combined with a slow dehydration, leads to enhance the somatic embryos' desiccation tolerance.     

Flight initiation and survival in the bark beetle Ips typographus (Coleoptera: Scolytidae) during the spring dispersal

Temperatures in the forest litter of Norway spruce Picea abies were recorded throughout the day to obtain environmental parameters that could be used to design realistic flight-activity experiments in the laboratory. Flight activity and survival were monitored electronically in plastic chambers where the conditions were controlled by an environmental chamber. Flight attempts of the bark beetle Ips typographus were initially lower in chambers with forest duff but were prolonged compared with those of beetles in chambers with a metal screen substrate. Small bark slabs and spruce twigs in the duff were utilized as food and extended the period of flight and survival. A thermal gradient in duff from 25° at the surface down to 13.8°C at a depth of 4 cm also slightly increased the survival of beetles compared with a constant 25°. A daily ambient temperature cycle as well as the duff thermal gradient increased the survival from about 3 d to more than 8 d. The latter length in the laboratory agreed with survival rates of caged beetles in a clearcut forest area, while beetles caged in the forest survival for more than 14 d. Temperatures were monitored at the duff surface of the caged beetles and compared with the catches of beetles that were attracted to a pheromone trap and collected with an electronic fraction collector. Information on flight and survival during the dispersal period is necessary to the design of ecologically sound management programs for control of bark beetles.     

Attraction of the bark beetle Tomicus piniperda and some other bark- and wood-living beetles to the host volatiles α-pinene and ethanol

The attraction of some bark- and ambrosia beetles as well as associated beetles to the host volatiles -pinene and ethanol was studied in field tests with flight barrier traps. Tomicus piniperda (L.) (Scolytidae), Thanasimus formicarius (L.) (Cleridae), and Rhizophagus ferrugineus (Payk.) (Rhizophagidae) were attracted by -pinene, while Hylurgops palliatus (Gyll.) and Trypodendron lineatum (Oliv.) (Scolytidae) were attracted by ethanol and Epuraea spp. (Nitidulidae) by both -pinene and ethanol. Combinations of -pinene and ethanol attracted high numbers of H. palliatus, T. lineatum, R. ferrugineus, Epuraea spp., and Glischrochilus spp. (Nitidulidae) and the catches increased with increasing release rates of ethanol. By contrast, lower numbers of T. piniperda were caught in traps baited with combinations of -pinene and ethanol than in traps baited with -pinene alone, and the catches of this species decreased with increasing release rates of ethanol. Traps baited with a combination of -pinene and ethanol or with -pinene alone caught similar numbers of T. formicarius. The results are discussed on the basis of species differences in preference for breeding substrate.

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Zusammenfassung Die Anlockung mehrerer Borkenkäfer und assoziierter Käferarten zu den flüchtigen Wirtsstoffen -Pinen und Äthanol wurde in Feldversuchen mit Flugbarrierenfallen studiert. Tomicus piniperda (L.) (Scolytidae), Thanasimus formicarius (L.) (Cleridae) und Rhizophagus ferrugineus (Payk.) (Rhizophagidae) wurden durch -Pinen angelockt, die Borkenkäfer Hylurgops palliatus (Gyll.) und Trypodendron lineatum (Oliv.) durch Äthanol und die Epuraea-Arten (Nitidulidae) durch sowohl -Pinen als auch Äthanol.Kombinationen von -Pinen und Äthanol lockten viele Individen von H. palliatus, T. lineatum, R. ferrugineus, Epuraea spp. und Glischrochilus spp. (Nitidulidae) an, und die Fänge nahmen mit zunehmender Äthanol-Abgabe zu. Umgekehrt wurden weniger T. piniperda in Fallen mit Kombinationen von -Pinen und Äthanol gefangen als in Fallen mit -Pinen allein, und die Waldgärtner-Fänge nahmen mit zunehmender Äthanol-Abgabe ab. Die Fänge von T. formicarius in Fallen mit einer Kombination von -Pinen und Äthanol unterschieden sich nicht von denen in Fallen mit nur -Pinen.Die Ergebnisse werden auf der Grundlage der Unterschiede zwischen den Arten in der Wahl des Brut-substrats besprochen.

     

Host selection and colonization strategies with evidence for a female-produced oviposition attractant in a longhorn beetle

In longhorn beetles and many other internally feeding insects, oviposition choice by females is critical to the survival of their offspring because their larvae are incapable of moving between hosts. Here we report on the complex host selection and colonization strategies of a longhorn beetle, Glenea cantor (F.) (Coleoptera: Cerambycidae), which is an important pest of kapok trees [Bombax ceiba L.=Gossampinus malabaricus (DC.) Merr.] in southern Asia. It attacks weakened trees, eventually killing them. The typical oviposition behavioral sequence in the laboratory includes the following: oviposition site search and recognition using antennae and palpi, oviposition slit preparation with mandibles, turning body direction 180°, egg deposition with the ovipositor, and oviposition wound covering with a jelly-like material from the ovipositor. Bark moisture content significantly increases from the upper to lower sections in kapok trees. In accordance with this variation female adults select the upper section of trees first for oviposition. As infestation continues and the host becomes more weakened, ovipositing females move further down the tree for oviposition. Consequently, the larvae kill the hosts from the top down. We show that the jelly-like material or eggs or both have an olfactory role in attracting females to oviposit nearby. Our findings are important in terms of increasing our understanding of host selection and colonization mechanisms of internally feeding insects, particularly cerambycids, and the development of environmentally friendly pest management measures.     

Tree leaf litter composition drives temporal variation in aquatic beetle colonization and assemblage structure in lentic systems

Tree leaf litter inputs to freshwater systems are a major resource and primary drivers of ecosystem processes and structure. Spatial variation in tree species distributions and forest composition control litter inputs across landscapes, but inputs to individual lentic habitat patches are determined by adjacent plant communities. In small, ephemeral, fishless ponds, resource quality and abundance can be the most important factor affecting habitat selection preferences of colonizing animals. We used a landscape of experimental mesocosms to assess how natural populations of aquatic beetles respond over time to variation in tree leaf litter composition (pine or hardwood). Patches with faster-decomposing hardwood leaf litter were initially colonized at higher rates than slower-decomposing pine pools by most species of Hydrophilidae, but this pattern reversed later in the experiment with higher colonization of pine pools by hydrophilids. Colonization did not differ between pine and hardwood for dytiscids and the small hydrophilid Paracymus, but there were distinct beetle assemblages between pine and hardwood patches both early and late in the experiment. Our data support the importance of patch quality and habitat selection as determinants of species abundances, richness, and community structure in freshwater aquatic systems, not only when new habitat patches are formed and initial conditions set, but as patches change due to interactions of processes such as decomposition with time.     

Enhancing stem cell survival in vivo for tissue repair

The ability to use progenitor cells for regenerative medicine remains an evolving but elusive clinical goal. A serious obstacle towards widespread use of stem cells for tissue regeneration is the challenges that face these cells when they are placed in vivo into a wound for therapy. These environments are hypoxic, acidic, and have an upregulation of inflammatory mediators creating a region that is hostile towards cellular survival. Within this environment, the majority of progenitor cells undergo apoptosis prior to participating in lineage differentiation and cellular integration. In order to maximize the clinical utility of stem cells, strategies must be employed to increase the cell's ability to survive in vivo through manipulation of both the stem cell and the surrounding environment. This review focuses on current advances and techniques being used to increase in vivo stem cell survival for the purpose of tissue regeneration.     

Symbiont survival and host-symbiont disequilibria under differential vertical transmission

Interspecific genetic interactions in host-symbiont systems raise intriguing coevolutionary questions and may influence the effectiveness of public health and management policies. Here we present an analytical and numerical investigation of the effects of host genetic heterogeneity in the rate of vertical transmission of a symbiont. We consider the baseline case with a monomorphic symbiont and a single diallelic locus in its diploid host, where vertical transmission is the sole force. Our analysis introduces interspecific disequilibria to quantify nonrandom associations between host genotypes and alleles and symbiont presence/absence. The transient and equilibrium behavior is examined in simulations with randomly generated initial conditions and transmission parameters. Compared to the case where vertical transmission rates are uniform across host genotypes, differential transmission (i) increases average symbiont survival from 50% to almost 60%, (ii) dramatically reduces the minimum average transmission rate for symbiont survival from 0.5 to 0.008, and (iii) readily creates permanent host-symbiont disequilibria de novo, whereas uniform transmission can neither create nor maintain such associations. On average, heterozygotes are slightly more likely to carry and maintain the symbiont in the population and are more randomly associated with the symbiont. Results show that simple evolutionary forces can create substantial nonrandom associations between two species.     

Glycerol and glucose accumulation during diapause in a tropical beetle

Abstract. Carbohydrate changes were measured during the 10-month adult diapause in the neotropical beetle, Stenotarsus rotundus Arrow (Endomychidae, Coleoptera) to test the hypothesis that metabolic suppression causes the accumulation of polyols in the absence of the need for cold tolerance. Glycerol and glucose both accumulate during the first 3 months from June to September, but decline in October, accumulate again in December-January and finally decline after January and stay low until the adults leave their diapause site in April. Any adaptive significance for this pattern is unknown but its coincidence with previously measured metabolic suppression suggests that glycerol and glucose accumulate as a result of metabolic adjustments during diapause. The relevance of these results to the evolution of polyol accumulation for cryoprotection in temperate insects in discussed.     

The role of beetle and host volatiles in host colonization in the European oak bark beetle, Scolytus intricatus (Ratzeburg) (Col., Scolytidae)

Abstract:  To understand the role of chemical signals involved in Scolytus intricatus (Ratzeburg) (Col., Scolytidae) host colonization, the attractiveness of intact and beetle colonized host material was investigated in the field and in the laboratory. In the field, chemical signals operating at long range were investigated by means of sticky traps. In the laboratory, close-range chemical interactions were investigated with an arena olfactometer. Field experiments showed no differences in the attractiveness between infested and non-infested host material. On the contrary, laboratory experiments revealed higher attractiveness of infested host and beetle-produced frass in comparison with intact host and mechanically produced sawdust respectively. Laboratory data also disclosed the attractiveness of beetle extracts of both sexes. Our data show that: (1) host kairomones play an important role during host colonization, and that (2) S. intricatus does not use a sex-specific secondary attractant system. Differences between results of field and laboratory trials are discussed.     

A reproductive tradeoff in an herbivorous lady beetle: egg resorption and female survival

A reproductive tradeoff between current egg production and subsequent survival in a lady beetle, Epilachna niponica, a specialist herbivore on a thistle, Cirsium kagamontanum, was investigated at the two study sites, A and F. Survival of reproductive females decreased consistently from early May until mid-June, but apparently increased thereafter. In contrast, males showed a consistent decrease in survival throughout the reproductive season, without any sign of recovery. Dissection of ovaries of sampled females revealed that egg resorption increased late in the reproductive season, coincident with increased female survival. Reproductive females stopped oviposition immediately after a large flood in 1979 at site F. Two weeks after the habitat perturbation, females resumed oviposition in response to a flush of new leaves on damaged plants. Female survival sharply increased during the nonoviposition period, and declined when egg-laying resumed. Approximately 40% of long-lived reproductive females at site F survived up to the following reproductive season in the next year. Also, some of these long-lived females were observed ovipositing in the following reproductive season. The long-lived reproductive females which had previously invested in reproduction survived equally well as newly emerged females which had not reproduced in summer. These results suggest that there is a reproductive tradeoff between current egg production and subsequent survival. Egg resorption may be an adaptive ovipositional response to habitat perturbation such as flooding, which considerably reduces offspring fitness due to absolute shortage of food. Also, increased female survival accompanied by egg resorption enhances the likelihood of the future oviposition in the second reproductive season, thereby increasing a female's lifetime reproductive success.     

Competition during colonization vs competition after colonization in disturbed environments: A metapopulation approach

How two species interact during and after colonization influences which of them will be present in each stage of succession. In the tolerance model of ecological succession in a patchy environment, empty patches can be colonized by any species, but the ability to tolerate reduced resource levels determines which species will exclude the other. Here, we analyze a meta-population model of the possible roles of competition in colonization and succession, using non-linear Markov chains as a mathematical framework. Different kinds of competition affect the final equilibrial, abundances of the species involved in qualitatively different ways. An explicit criterion is given to determine which interactions have stronger effects on the final equilibrial levels of the weaker, species. Precise conditions are stated for the co-existence of both species. Both species are more likely to co-exist in the presence of an intermediate disturbance frequency.     

Consequences of adult size for survival and reproductive performance in a herbivorous ladybird beetle

Abstract.

• 1 A univoltine herbivorous ladybird beetle Epilachna niponica (Coleoptera: Coccinellidae) shows a large variation in adult size within a population.
• 2 Large adults had higher survival from emergence to the reproductive season, and the size-dependent adult survival was most apparent during hibernation. On the other hand, adult survival during pre-hibernation contributed little to size-dependent overall survival.
• 3 Neither reproductive lifespan nor lifetime fecundity were a function of adult size, though large females produced larger size of egg batches.
• 4 Size of adult beetles was significantly reduced by leaf damage to plants on which they grew up on larval stage. Since leaf herbivory increases through the season, late emerged adults that were subjected to food deterioration during the larval period were smaller than early-emerged individuals.