The Banded Elm Bark Beetle, Scolytus schevyrewi Semenov (Coleoptera, Curculionidae, Scolytinae) in North America: a taxonomic review and modifications to the Wood (1982) key to the species of Scolytus Geoffroy in North and Central America

In 2003, an Asian bark beetle, Scolytus schevyrewi Semenov (Coleoptera: Curculionidae: Scolytinae), the banded elm bark beetle, was detected for the first time in North America. This paper modifies the Wood (1982) key to the species of Scolytus Geoffroy to enable identification of Scolytus schevyrewi in North and Central America. Variation of diagnostic characters in Scolytus schevyrewi is discussed.     

Scolytus stepheni sp. n. - a new species of bark-beetle (Coleoptera, Curculionidae, Scolytinae) from Northern India with a key to Indian Scolytus Geoffroy, 1762 species

A new species of bark-beetle from Kashmir, Scolytus stephenisp. n., dedicated to the late Professor Emeritus Stephen Lane Wood, is described and figured. Key to Indian Scolytus Geoffroy, 1762 species is provided.     

New data on Neotropical Scolytus Geoffroy, 1762 with description of five new species from Peru (Coleoptera, Curculionidae, Scolytinae)

Five new species of Scolytus Geoffroy, 1762 (Coleoptera: Curculionidae: Scolytinae) are described from Peru, namely Scolytus woodi, Scolytus carveli, Scolytus vagabundus, Scolytus lindemani, Scolytus mozolevskae .The following new synonym is established: Scolytus angustatus Browne, 1970 (= Scolytus facialis Schedl, 1973, syn. n.) New records of the Scolytus species in Loreto, Junin ,Cusco and Madre de Dios Provinces are given and the biology of the genus representatives is discussed.     

A Key to and Annotated List of the Species of the Bark-Beetle Genus Scolytus Geoffroy, 1762 (Coleoptera,Curculionidae: Scolytinae) from European Russia

Entomological Review - A key to and an annotated list of species of the genus Scolytus Geoffroy, 1762 from European Russia are given.     

Phoretic mites and nematode associates of Scolytus multistriatus and Scolytus pygmaeus (Coleoptera: Scolytidae) in Austria

Abstract 1 The species assemblages and abundance of phoretic mites and nematodes associated with the elm bark beetles, Scolytus multistriatus and Scolytus pygmaeus, were studied in Austria. 2 A total of 3922 individual mites were recorded from 144 adults of S. multistriatus and 178 adults of S. pygmaeus. The species spectrum was identical and the relative abundance of mites was very similar for both species of scolytids. Nine mite species, Pyemotes scolyti, Pseudotarsonemoides eccoptogasteri, Trichouropoda bipilis, Tarsonemus crassus, Proctolaelaps eccoptogasteris, Proctolaelaps scolyti, Chelacheles michalskii, nr. Eueremaeus sp. and Elattoma sp. were detected. Two of the nine species, nr. Eueremaeus sp. and Elattoma sp., are documented here as new associates of Scolytus spp. 3 Pyemotes scolyti was the most frequent mite species, and Ps. eccoptogasteri and T. bipilis were relatively common, whereas the other mites occurred occasionally or were rare. 4 The trophic roles of most of the mites associated with S. multistriatus and S. pygmaeus are poorly known, but they may include fungivores, parasitoids of bark beetle broods, predators of bark beetle broods and/or mites and/or nematodes. 5 Besides phoretic mites, two nematode associates were seen on the investigated insects. A species of Cryptaphelenchus occurred under the elytra of both scolytid species, whereas the adults of a Neoparasitylenchus sp. were present inside abdomens of S. multistriatus, but absent from S. pygmaeus.     

Description of Longidorus fagi n. sp. (Nematoda, Dorylaimida) with an identification key to the species of the genus occurring in Bulgaria

Longidorus fagi n. sp. is described from Vitosha Mountain, Bulgaria, where it was found in soil around roots of Fagus sylvatica L. The new species is characterised by its medium size, narrow anteriorly rounded lip region which is offset from the body by a very slight depression, large amphidial pouches which are distinctly bilobed at the base, and a conoid-elongate tail which is ventrally curved with a narrow, rounded terminus. L. fagi resembles L. nirulai, L. distinctus, L. curvatus and L. fragilis, An identification key for species of the genus Longidorus present in Bulgaria is provided.     

The susceptibility of the elm bark beetle Scolytus scolytus to the DD-136 strain of Neoaplectana sp.

Adults and larve of Scolytus scolytus were highly susceptible to the DD-136 strain of Neoaplectana sp. in the laboratory.     

Behavioral responses of the smaller European elm bark beetle, Scolytus multistriatus, to extracts of non-host tree tissues

Crude benzene extracts of 6 non-host trees alone did not stimulate feeding responses by adults of Scolytus multistriatus (Marsh.). When combined equally with a stimulatory extract from Ulmus americana L., all of the crude non-host extracts reduced the amount of feeding which otherwise occurred. At least two of the non-hosts (Populus deltoides Bartr. and Aesculus octandra Marsh) contained positive short-range orientational stimuli, but their induction of a positive response by the insect was prevented in most treatments by associated deterrent chemicals. Thus, stimuli (deterrents and repellents) played the dominant role in eliciting the rejection of crude non-host extracts by the beetles.

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Zusammenfassung Benzol-Rohextrakte von 6 Nicht-Wirtsbäumen riefen allein bei erwachsenen Scolytus multistriatus (Marsh.) keine Fraßreaktionen hervor. Wurden sie zu gleichen Teilen mit einem stimulierenden Extrakt von Ulmus americanus L. kombiniert, so setzten alle Rohextrakte aus Nicht-Wirten die Fraßmenge herab, die sonst auftritt. Wenigstens zwei der Nicht-Wirte (Populus deltoides Bartr. und Aesculus octandra Marsh.) enthielten auf kurze Entfernung wirkende positive Reize, aber ihr Einfluß auf eine positive Reaktion des Insekts wurde bei den meisten Behandlungen durch Verbindung mit abweisenden (deterrent) Stoffen verhindert. So spielen bei der Auslösung der Ablehnung von Rohextrakten der Nicht-Wirte durch die Käfer Deterrent- und Repellent-Reize die Hauptrolle.

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Approved for publication by the Director of the Wisconsin Agricultural Experiment Station. This research was supported in part by a research grant (GB-6580) from the National Science Foundation; and from funds provided by the State of Wisconsin Department of Natural Resources.     

脐腹小蠹形态特征和生物学特性

脐腹小蠹Scolytus schevyrewi Seme.是榆树的一种重要蛀干害虫。本研究在宁夏盐池县通过室内观察和林间调查相结合,研究了脐腹小蠹的形态特征及其生活史、成虫寿命、习性、交尾行为等生物学特性。结果显示:脐腹小蠹虫在宁夏盐池县一年发生2代,以老熟幼虫或蛹越冬,老熟幼虫约占98.2%,蛹约占1.8%。越冬幼虫于5月上旬开始化蛹,5月中旬为化蛹盛期,5月下旬开始羽化,6月上旬为羽化盛期。第2代幼虫于6月底、7月初开始化蛹,7月下旬达羽化盛期,8月上旬羽化结束;脐腹小蠹雌成虫平均寿命为(27.14±3.74)d,雄成虫的平均寿命为(16.86±4.13)d,差异显著(P<0.05);此外,脐腹小蠹无滞育现象;脐腹小蠹的4种天敌,分别是榆小蠹长茧蜂Elachistocontrum sp.、虱形螨Pedieuloids ventricosus Newport、拟截斑郭公虫Thansimus sp.和蠼螋Labidura sp.。     

Lignin intermediates and simple phenolics as feeding stimulants for Scolytus multistriatus

Comparative stimulation of Scolytus multistriatus feeding by tested dihydroxybenzenes and benzaldehydes showed that molecules with 1,4 substitutions on the benzene ring were most active; 1,3 and 1,2 substitutions were progressively less active. Methoxyl substitution adjacent to the 4-hydroxyl group on benzaldehydes reduced feeding and replacement of a hydroxyl by a methoxyl group on 1,2 disubstituted phenols destroyed the feeding response. Methoxyl substitution on benzaldehydes increased volatility and short-range attraction, but reduced feeding activity in the laboratory bioassays.     

Biological control of Dutch elm disease: Bacillus thuringiensis as a potential control agent for Scolytus scolytus and S. multistriatus

J assim , H.K., F oster , H.A. & F airhurst , C.P. 1990. Biological control of Dutch elm disease: Bacillus thuringiensis as a potential control agent for Scolytus scolytus and S. multistriatus. Journal of Applied Bacteriology 69 , 563–568.
The effects of exposing fifth instar larvae of Scolytus scolytus and S. multistriatus to spore suspensions of Bacillus spp. were investigated. Bacillus thuringiensis ser 3a, 3b increased the mortality of larvae cultured on an artificial medium from approximately 20% in control cultures to over 80% in cultures exposed to the bacteria. The mortality was dose-dependent for S. multistriatus and the approximate LC₅₀ value was 2.2 times 10³ spores/ml. Different serotypes of B. thuringiensis caused different levels of mortality: H6 produced the highest mortality and H1 the lowest. Bacillus alvei and B. cereus were also pathogenic but B. megaterium was not. The results are discussed in relation to the mechanism of pathogenicity and the potential for the use of B. thuringiensis for the control of the vectors of Dutch elm disease.     

Ultrastructure of sensory receptors on the antennae of Scolytus multistriatus (Marsh.)

Summary The antennae of Scolytus multistriatus were examined with light and scanning and transmitting-electron microscopy to determine the distributions, types and structures of sense organs. Four types of sensilla were found: (1) sensilla chaetica, a singly-innervated receptor; (2) sensilla basiconica, Type A, a short, thin-walled, multiple-innervated receptor; (3) sensilla basiconica, Type B, a long, thin-walled multiple-innervated receptor; and (4) sensilla trichodea, short, thick-walled, multiple-innervated receptors. The positioning of dendrite(s) with regard to pore tubules is elaborated. Evidence for lack of sensory axon fusion is presented.Approved for publication by the Director of the Research Division, College of Agricultural and Life Sciences. This research was supported in part by a research grant (GB-8756) from the National Science Foundation, and by funds from the Elm Research Institute. The authors wish to thank Dr. G. A. deZoeten and Mr. G. A. Gaard for their assistance and encouragement.     

中国叶蚜亚科分类学研究(同翅目,蚜科)

中国叶蚜亚科Phyllaphidinae已知4属,迪叶蚜属Diphyllaphis Takahashi,1960,楠叶蚜属Machilaphis Takahashi,1960,叶蚜属Phyllaphis Koch,1856和群斑蚜属Thelazacallis Zhang,2000;4个种,栎迪叶蚜Diphyllaphis quercus (Takahashi,1960),楠叶蚜Machilaphis machili(Takahashi,1928),山毛榉叶蚜Phyllaphis fagi(Linnacus,1767)和毛茛群斑蚜Thelazacallis ranunculicola Qiao et Zhang,2000.其中叶蚜属和山毛榉叶蚜为中国新纪录.文中提供了分属检索表,各属提供了鉴别特征,所有分类单元提供了文献引证、寄主植物、地理分布和检视标本的记录.新纪录种有详细的形态记述和特征图.研究标本保存在中国科学院动物研究所动物标本馆.     

Effect of nutrition of parasites with nectar of melliferous plants on parasitism of the elm bark beetles (Col., Scolytidae)

In the forest of Kljestevica, the elm is attacked by four species of elm bark beetles: Scolytus multistriatus (Marsh.), Scolytus scolytus (Fab.), Scolytus pygmaeus (Fab.) and Scolytus ensifer (Rich.) (Col., Scolytidae). Scolytus multistriatus and S. pygmaeus are the most numerous species. Elm bark beetle is parasitized by four species of parasites: Dendrosoter protuberans (Nees), Ecphylus silesiacus (Ratz.), Coeloides scolyticida (Wesm.) (Hym., Braconidae) and Entedon leucogramma (Ratz.) (Hym., Eulophidae). Ecphylus silesiacus and D. protuberans are the most numerous species. The nectar of mustard ( Sinapis alba L., Brassicaceae) flowers, sweet basil ( Stachys recta L., Lamiaceae) flowers and of wild carrot ( Daucus carota L., Umbelliferae), has an important effect on the number of parasites and on the parasitism of the elm bark beetles. Wild carrot is the most attractive plant to the parasites for additional nutrition, especially for D. protuberans . Mustard and sweet basil flowers are suitable for additional nutrition of E. silesiacus imagos. On meadow flowers growing spontaneously in forest clearings, the lowest number of parasite imagos was collected by an entomological catcher, and the lowest percentage of parasitized larvae and eggs of the elm bark beetle was recorded in elm control catch trunks that were not near the cultivated melliferous plants.     

Biological control of Dutch elm disease: Larvicidal activity of Trichoderma harzianum, T. polysporum and Scytalidium lignicola in Scolytus scolytus and S. multistriatus reared in artificial culture

A method is described for the culture of larvae of Scolytus multistriatus and Scolytus scolytus on an artificial medium following exposure to cultures of microorganisms. In control cultures, a natural mortality rate of 21.2% was found for S. multistriatus and 17.6% for S. scolytus. The effects of Trichoderma harzianum, T. polysporum and Scytalidium lignicola on fifth instar larvae of S. scolytus and S. multistriatus reared on the artificial medium were studied. The fungi were larvicidal and larval mortality was increased to more than 80% by inoculation of the larvae with the fungi. Another fungus, Phomopsis oblonga, had little effect on larvae of S. scolytus. The results are discussed in relation to mechanism of pathogenicity of the fungi and their potential use in the control of Dutch elm disease. It is proposed that with modifications, the method is applicable to other bark beetle pests.     

Significance of parasitoids in the reduction of oak bark beetle Scolytus intricatus Ratzeburg (Col., Scolytidae) in Serbia

Abstract:  As the vector of vascular fungi of the genus Ophiostoma the oak bark beetle, Scolytus intricatus , is one of the significant links in the chain of agents of oak forest decline in Serbia. It is known that the adults of this bark beetle, which develop under the bark of the trees infected by fungi of the genus Ophiostoma , transport the spores of these fungi. During the maturation feeding, the spores are transmitted to healthy tree crowns, where they germinate and cause infection. In period 1992–96 at 27 localities in Serbia, the significance of parasitoids in the reduction of this bark beetle was examined, as the intensity of spore transmission depends upon the number of oak bark beetle adults in nature. In the research of parasitoids of S. intricatus 20 species were identified in five families of Hymenoptera: Braconidae (six species), Eurytomidae (one), Pteromalidae (10), Eupelmidae (one) and Eulophidae (two). Among these parasitoids the greatest influence on the abundance of oak bark beetle was the species Ecphylus silesiacus . It was identified in 90.91% of study samples, its domination was 39.15% and the percentage of oak bark beetle parasitism was 5.66%. In addition, the species Entendon ergias , Dendrosoter protuberans and Cheiropachus quadrum were significant in reduction of S. intricatus . The average percentage of parasitism of oak bark beetle by E. ergias was 2.74%, by D. protuberans it was 2.63% and by Ch. quadrum 1.63%. The significance of other parasitoids in the reduction of oak bark beetles was low. In the study period the total parasitism of oak bark beetle varied between a minimum of 8.64% in 1992 and a maximum of 19.64% in 1996. The average for the whole study period was 14.49%.     

The DD-136 strain of Neoaplectana sp. as a potential biological control agent for the European elm bark beetle,Scolytus scolytus

When logs infected with Scolytus scolytus were sprayed with the DD-136 strain of Neoaplectana sp. in solutions of either distilled water, glycerin, or P.B.I. wetting agent, the nematodes were efficiently dispersed and entered the logs through the insect entrance holes in the bark.Logs treated with Neoaplectana sp. were found to contain a significantly higher proportion of dead, nematode-infected insects. No difference was found between the various methods of nematode application. The results indicate that Neoaplectana sp. may have a possible role in the control of S. scolytus in elm logs.     

Some effects of freezing temperatures on overwintering larvae of the large elm bark beetle (Scolytus scolytus)

Overwintering final instar larvae of Scolytus scolytus were tested for coldhardiness by exposure to a range of sub-zero temperatures (–7°Cto –31 °C) in a frost-gradient apparatus for 7 days. The Lt₅₀ for larvae removed from the bark (– 20.5 °C) was significantly different (P < 0.01) from the Lt50 (–18.3 °C) for larvae insulated by the bark (thickness of 7 mm ± 2 mm). Larvae with food in their digestive tract were more susceptible to freezing than the overwintering final instars which had voided their stomach contents. Duration and intensity of cold did not cause any adverse long-term effects. Most of the larvae which survived the sub-zero treatments were able to pupate or reach the adult stage. The mean supercooling point of the overwintering larvae (–30.85 °C) confirmed their cold-hardiness.     

Feeding by Scolytus bark beetles to test for differently susceptible elm varieties

Dutch elm disease (DED), caused by the fungi Ophiostoma ulmi and O. novo‐ulmi, has reduced elm populations severely in Europe and North America. Breeding programmes are in action to find less susceptible elm varieties suitable for re‐establishing elm stands. Bark beetles, mainly Scolytus spp., are the only known natural vectors of DED. During twig feeding, beetles transfer Ophiostoma spores to healthy elms. Thus, less palatable elms should run a lower risk of DED infections. In feeding preference bioassays, we offered twigs from elms exhibiting different degree of susceptibility to O. novo‐ulmi, together with non‐host trees to Scolytus beetles. Scolytus multistriatus preferred wych elm, Ulmus glabra, to 100% in two‐choice tests, whereas S. laevis did not discriminate between a tolerant and a susceptible variety of field elm, U. minor. We suggest that the feeding assay is useful as a low‐tech method in breeding programmes for evaluating the suitability of promising elm genotypes to vector insects.     

Laboratory studies on the fungus Verticillium lecanii, a larval pathogen of the large elm bark beetle (Scolytus scolytus)

From 1972 to 1974, estimates of the natural larval mortality (> second instar) of elm bark beetles caused by pathogenic organisms were always below 7'5 % of the beetle population. The pathogenic fungus Verticillium lecanii was frequently isolated from field-collected dead larvae, and in the laboratory all larvae were killed in 5 days when exposed to spore concentrations of 4·5 × 10⁶ spores/ml. V. lecanii begins to lose its pathogenicity after prolonged culture on artificial media. The time taken for V. lecanii to kill Scolytus scolytus larvae when exposed to a logarithmic series of spore dilutions from 9·1 × 10⁷/ml to 9·1 × 10³/ml increased with decreasing amounts of inoculum. Even at spore concentrations as low as 9·1 × 10³/ml the mortality of treated larvae was greater than that of untreated individuals. At 100% r.h. all treated larvae were killed over a temperature range of 5–30 °C; those maintained at 25 °C were killed most rapidly and those kept at 5 °C the slowest.