Artificial diet and rearing methods for Thanasimus dubius (Coleoptera: Cleridae), a predator of bark beetles (Coleoptera: Scolytidae)

Clerid beetles are common natural enemies of bark beetles, and could potentially be used as biological control agents if they could be reared in sufficient numbers. We developed an artificial diet devoid of insect components for rearing Thanasimus dubius (Fabricius), a clerid that attacks several economically important bark beetles in eastern North America. We reared larvae of this predator using the artificial diet, and then used either natural or factitious prey to feed the adults so produced. Two different methods of presenting the diet were also examined. We then compared the performance of T. dubius reared on the artificial diet with newly-emerged wild individuals collected from the field. Our results suggest that adult predators reared on the diet are near in quality to wild ones, and high R₀ values can be obtained. No difference in prey preference was found between wild and diet-reared individuals after five generations in the laboratory. Sufficient numbers of predators could be generated using these techniques to permit limited field trials of augmentative biological control.     

Continuous population estimates forDendroctonus frontalis Zimm. (Coleoptera: Scolytidae) occurring in infestations

Infestations of Dendroctonus frontalisZimm. are often observed to enlarge continuously by the colonization of new hosts in a pattern similar to a forest fire. This pattern of infestation growth presents unique problems in quantitatively estimating populations of D. frontalis. Beetle populations on each infested tree in an infestation go through five processes: attack, oviposition, reemergence, survivorship, and emergence. These processes, which have been described mathematically in the literature, each take several days for completion. In order to follow the distribution and abundance of D. frontalis throughout the course of development of a spot, we need a daily estimate of the number of beetles involved in each process on every tree. Since it is not practical to sample each tree daily, we developed a procedure whereby quantitative estimation procedures for within-tree populations were used in combination with the mathematical models for the life processes to produce a daily record of the number of adults successfully attacking trees, the number of eggs oviposited, the number of beetles reemerging, number of beetles surviving within the trees, and the number of beetles emerging. These daily estimates were then summarized for all trees in the spot for the duration of the infestation. The daily record of populations of D. frontalis, used with information on infestation geometry, were suggested to be of value in describing and elucidating several important facets of population dynamics including dispersal patterns within infestations, between tree beetle loss (mortality), and time lags among the various population processes. The information reported can be used to develop simulation models of population dynamics or to validate existing models.     

Helicosporidium infection of the great European spruce bark beetle, Dendroctonus micans (Coleoptera: Scolytidae)

An infection of the great European spruce bark beetle Dendroctonus micans (from Turkey) by the parasitic green alga Helicosporidium is described. This is the first time that Helicosporidium has been found to infect a bark beetle (Scolytidae) and the first time that a naturally infected beetle has been reported for the Eurasian continent. The typical cysts of Helicosporidium contain three ovoid cells and one helical, filamentous cell. The morphological characteristics are revealed by light and electron microscopy. Distinct electron-dense inclusions with a peculiar ultrastructure may represent pyrenoids. Since D. micans is an important pest, the discovery of a natural pathogen may offer a chance for biological control.     

The first study on the bacterial flora of the european spruce bark beetle, Dendroctonus micans (Coleoptera: Scolytidae)

The European spruce bark beetle, Dendroctonus micans Kugelann (Coleoptera, Scolytidae), is one of the most serious pests of oriental spruce (Picea orientalis L.) in Turkey. In this study, we investigated bacterial flora of D. micans collected from different populations of the forests of Eastern Black Sea Region of Turkey from 2002 to 2004. Seven different bacteria were isolated from healthy, diseased and dead specimens based on the color of colony and morphology. According to morphological, physiological and biochemical properties, metobolic enyzme profile by BIOLOG microtiter plate system, and total cellular fatty acid profile by Microbial Identification System (MIS), isolates were identified as Micrococcus luteus, Bacillus thuringiensis subsp. morrisoni, Serratia grimesii, Enterobacter cloaceae, Enterobacter intermedius, Streptococcus sp. and Pseudomonas putida. This is the first study on the bacterial flora of D. micans.     

Kinetics of larval gregarious behavior in the bark beetleDendroctonus micans (Coleoptera: Scolytidae)

This paper provides a simple mathematical model of the aggregation behavior of the gregarious intracortical-feeding larvae of the bark beetle, Dendroctonus micans. The model's assumptions are that each individual produces pheromones at a constant rate and reacts positively to a pheromone gradient. These hypotheses have been tested by comparing experiments and simulations, both of which showed that (1) homogeneously distributed individuals aggregate rapidly at the center of the experimental or theoretical arena and (2) eccentric, preformed groups succeed in attracting dispersed individuals, provided that the initial size of these groups is sufficiently high. There is good agreement between most of the experimental and theoretical results, providing a link among chemical communication, density of larvae, and random events occurring during the development of a spatial structure.     

Mathematical description of within-tree distributions of the various developmental stages ofDendroctonus frontalis Zimm. (Coleoptera: Scolytidae)

Probability density functions for the various within-tree developmental life stages of D. frontalis are derived. The differences between some of these distributions are discussed. The possibility of the existence of a negative feed-back mechanism which enables the beetle to make optimum utilization of the available resources is proposed. In addition, the concept of an optimum location on the infested bole where the environmental (tree) conditions are such that maximum survivorship occurs is advanced.     

Climate and the northern distribution limits of Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae)

The southern pine beetle, Dendroctonus frontalis, is among the most important agents of ecological disturbance and economic loss in forests of the south-eastern United States. We combined physiological measurements of insect temperature responses with climatic analyses to test the role of temperature in determining the northern distribution limits of D. frontalis. Laboratory measurements of lower lethal temperatures and published records of mortality in wild populations indicated that air temperatures of ?16° should result in almost 100% mortality of D. frontalis. The distribution limits for D. frontalis approximate the isoline corresponding to an annual probability of 0.90 of reaching ≤?16 °C. Thus, D. frontalis have been found about as far north as they could possibly occur given winter temperature regimes. At latitudes from 39° N (southern Ohio) to 33° N (central Alabama), winter temperatures must exert high mortality on D. frontalis populations in at least one year out of ten. In contrast, we reject the hypotheses that summer temperatures or the distribution of host trees constrain the northern distribution of D. frontalis. Because of the short generation time of D. frontalis, its high dispersal abilities, and the cosmopolitan distribution of suitable host trees, changes in either the mean or variance of minimum annual temperatures could have almost immediate effects on regional patterns of beetle infestations. We estimate that an increase of 3 °C in minimum annual temperature could extend the northern distribution limits by 170 km. Increases or decreases in the variance of minimum annual temperatures would further relax climatic constraints on the northern distribution limits of D. frontalis. Results emphasize the ecological importance of spatial and temporal variability in minimum annual temperatures. The physiologically based models provide a tool for guiding land management decisions in forests and illustrate a general approach for predicting the regional effects of climatic patterns on the distribution of organisms.     

Partial age-specific life tables for Monochamus titillator in Dendroctonus frontalis infested loblolly pines

Partial age-specific life tables were constructed for Monochamus titillator(Fabricius) (Coleoptera: Cerambycidae) in Dendroctonus frontalisZimmermann (Coleoptera: Scolytidae) infested loblolly pine (Pinus taedaL.) trees. Successive life stages including egg, early larvae, mid-stage larvae, late larvae, and adult emergence were sampled within six sample trees. Generation mortality ranged from 60.94% to 98.61% in sample trees. Highest mortality typically occurred to eggs and mid-stage larvae. Possible mortality factors included resinosis, predaceous beetles, parasitoids, and woodpeckers. Dendroctonus frontalisbrood stages were determined for consecutive M. titillatorsampling. Monochamus titillatorand D. frontaliscoexisted and likely interacted in the phloem of host trees for at least 20 days.     

Estimatingdendroctonus frontalis (Coleoptera: Scolytidae) daily infestation dynamics

Summary Mathematical procedures are given to estimate infestation totals and daily life stage arrivals, departures, and mortality ofDendroctonus frontalis Zimmermann for an infested tree in the field. These estimates are based on minimal sample data and are designed to utilize all available information. Daily arrival estimates for larvae, pupae, and callow adults are obtained by indirect analysis without direct observation of these stages. The procedures are applied to 147 infested trees, and the results are transformed to a common time basis to obtain daily expectations by life stage for an “average” tree. These expectations suggest optimal times for field sampling or relative times of sampling when optimal times are missed. Expected daily arrival distributions by life stage for a single egg and a single attacking adult are given. Procedures are given for utilizing collateral information to obtain an infestation total and daily arrival estimates for a boundary life stage. The results of this study are applicable to anyD. frontalis field study, and the procedures given are applicable to any bark inhabiting insect having similar habits.     

Take-off capacity as a criterion for quality control in mass-produced predators,Rhizophagus grandis (Col.: Rhizophagidae) for the biocontrol of bark beetles,Dendroctonus micans (Col.: Scolytidae)

Time spent by adult beetles in cold storage at 3–7°C accounted for 81% of the loss of take-off capacity inRhizophagus grandis Gyllenhal in windtunnel experiments. At the age of three weeks, the insects were at their highest take-off capacity at about 80%. This was followed by a steady decrease, 7% of the insects failing to take-off each month. Changes in the fat reserves during cold storage could explain at least partly this reduction of flight capacity although there was no significant difference in fresh weight between insects that were able/unable to take-off. Sex had a significant influence on take-off rates, with an 8.7% higher take-off rate in females. Take-off capacity was further reduced when the insects were mass-produced in cultures using parent beetles submitted to a blend of synthetic oviposition stimulants instead of live prey larvae. Response to synthetic attractants by those insects which took-off, however, was not influenced by cold storage or by the use of synthetic stimulants in the culture medium.

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Résumé Le temps passé en conservation à basse température (3–7°C) depuis la métamorphose est intervenu pour 81% dans la perte de la capacité d'envol chez le coléoptère prédateurRhizophagus grandis Gyll. lors d'expériences en tunnel de vol. A l'age de trois semaines, les insectes sont à leur plus haut niveau d'envol (envol d'environ 80% des insectes). Par la suite, il y a un déclin constant de la capacité d'envol, à raison de 7% des insectes chaque mois. Des changements dans les réserves lipidiques peuvent partiellement expliquer cette réduction, bien qu'il n'y ait pas eu de différence entre le poids frais d'insectes capables de s'envoler et celui d'individus qui en étaient incapables. Le sexe a une influence sur le taux d'envol, avec un taux d'envol significativement plus élevé de 8.7% chez les femelles. La capacité d'envol est encore réduite chez des insectes qui ont été produits dans des élevages de masse où les parents étaient soumis à un mélange de stimuli de ponte de synthèse au lieu d'être mis en présence de larves deD. micans vivantes. Chez les insectes qui prennent leur vol, cependant, la réponse aux attractifs de synthèse est indépendante de l'age ainsi que des conditions d'élevage.

     

Description of Parasitorhabditis frontali n. sp. (Nemata: Rhabditida) from Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae)

A new Parasitorhabditis species with males and females was discovered from the southern pine beetle Dendroctonus frontalis and its galleries in loblolly pine, Pinus taeda, growing in Mississippi. Females of the new species have a cupola-shaped tail with a small spike; males possess a 2 + (3+2) + 3 ray pattern on the tail fan with ray 10 reaching the margin, and a distinctive stomatal tooth. Parasitorhabditis frontali n. sp. has some similarities to P. hylurgi Massey, 1974 from Hylurgops pinifex in New York, USA, P. terebranus Massey, 1974 from D. terebrans (Olivier, 1795) in Texas USA, P. ligniperdae Fuchs, 1915 from Hylergops ligniperda (Fabricius, 1787) and P. dendroctoni Rühm, 1956 from D. micans (Kugelann, 1794) in Europe, P. ateri Fuchs, 1915 isolated from the beetle Hylastes ater (Paykull, 1800) in Germany, and P. malii Devdariani and Kakulia,1970 from Scolytus mali (Bechstein, 1805) within the republic of Georgia. Morphometrics for 44 species of Parasitorhabditis are provided to update older keys. Parasitorhabditis frontali n. sp. was initially grown on Malt Extract (ME) agar with its own microbial contaminants that included a bacterium and fungus. The nematode also grew and reproduced after slices of ME agar with nematodes and microbial contaminants were transferred to water agar. It was killed by E. coli on NGM agar plates commonly used to raise other Rhabditida. Drawings of diagnostic anatomy and low-temperature SEM images of bodies, heads, and tails are provided for cultured specimens from pine beetle frass.     

Induced defenses of loblolly pine, Pinus taeda: potential impact on Dendroctonus frontalis within-tree mortality

Loblolly pine (Pinus taeda L.) produces an induced defensive hypersensitive response in inner bark colonized by the southern pine beetle, Dendroctonus frontalis Zimm. (Coleoptera: Scolytidae), and its associated fungi. Adult beetles forced to colonize the induced response tissue in a laboratory study constructed galleries that were the same length as adults boring in normal phloem. However, each female laid fewer eggs in the induced tissue. Larval and pupal mortality were also higher in this tissue when compared to surrounding phloem. Beetles colonizing trees in response to pheromone baits constructed less gallery and laid fewer eggs in induced tissue than in surrounding normal phloem. These results suggest that the lesions produced by the induced defense system in conifers may not only contain the growth of fungi inoculated into trees during the attack phase of beetle colonization, but may also affect survival of bark beetle progeny.

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Résumé Une réaction hypersensible de défense a été induite dans les couches profondes de l'écorce de P. taeda colonisée par D. frontalis et le champignon qui lui est associé. Au laboratoire, des adultes, contraints de coloniser les tissus où une réaction hypersensible e été induite, ont foré des galeries de même longueur que celles creusées dans du phloème sain. Cependant les femelles ont pondu moins d'oeufs dans les tissus induits; les mortalités larvaires et nymphales étaient aussi plus fortes dans ce tissu que dans le phloème voisin. Les scolytes, ayant colonisé les arbres après attraction par des pièges à phéromones, forent moins de galeries et pondent moins d'oeufs dans le tissu induit que dans le phloème sain voisin. Ces résultats suggèrent que les lésions, provoquées par le système de défense induit des conifères, peuvent non seulement limiter la croissance du champignon inoculé dans l'arbre au cours de la colonisation des scolytes, mais aussi affecter la survie des descendants dans l'écorce.

     

Biochemical approach to the control ofXyleborus fornicatus (Coleoptera: Scolytidae)

Summary The addition of small quantity of potassium acetate to the fertilizer applied to tea bushes was an effective method of reducing infestation by the beetle pest,Xyleborus fornicatus. The mechanism of action of potassium acetate is discussed as being due to its conversion to saponins and/or sterol analogues which interfere with pupation of the beetle larvae.     

Gallery construction and oviposition of the bark beetle Ips typographus (Coleoptera: Scolytidae) at different breeding densities

Abstract. 1. The bole of a Norway spruce, Picea abies (L.) Karst., was cut in 25 cm sections and infested in the laboratory with 2 or 8 females/dm² of Ips typographus (L.) and an equal number of males.
2. One log of each beetle density was dissected every second day, beginning 2 days after female introduction.
3. The oviposition rate was highest at the beginning of the breeding period for both densities and then declined, especially at the high density. Residence time is a useful approximation for the number of laid eggs in the beginning of the oviposition period or when the density is low.
4. Final gallery length and egg number per gallery were on average significantly smaller at density 8 than at density 2.
5. Linear relationships between total gallery length and number of egg niches were found to be similar for the two densities.
6. An estimate of the egg to adult mortality at different densities was found by using data from a field study that related gallery length to breeding density in attacked living trees, together with published relationships between density and egg niches or emergence of new adults.
7. It was concluded that both decreased oviposition rate and earlier re-emergence at higher densities contribute to a declining oviposition with increasing density. The final offspring production is futher reduced by lower survival due to larval competition as density increases.     

Fungi associated with the southern pine beetle: avoidance of induced defense response in loblolly pine

Summary Loblolly pines (Pinus taeda) are rapidly killed by colonizing southern pine beetle (Dendroctonus frontalis). The female beetles carry two species of fungi (Ceratocystis minor var. barrasii and an unnamed basidiomycete) within a mycangium. The insects are also frequently associated with a blue-staining form of C. minor. These fungi are inoculated into the tree during colonization. The tree has an induced defensive response that involves resin soaking and necrosis of affected tissue isolating the invading organlsms. The blue-staining fungus stimulates formation of this response in the tree, but the two mycangial fungi do not. These results suggest that the beetles are closely associated with two highly pathogenic fungi that do not stimulate one of the critical components of tree defense.     

Characterization of five microsatellite loci in the pine shoot beetle Tomicus piniperda (Coleoptera: Scolytidae)

Tomicus piniperda is a bark beetle that causes damage to various pine species across a wide geographical range. We developed five microsatellite polymorphic markers using an enrichment protocol. All loci could be successfully amplified with no evidence of null alleles and will be useful for population genetic studies. Cross‐species amplifications show that at least some of the markers could be useful in four other Tomicus species.     

Interactions betweenAulonium ruficorne [Coleoptera: Colydiidae] and other natural enemies of bark beetles [Coleoptera: Scolytidae]

The within tree distribution of some common natural enemies of bark beetles in pine plantations in Israel and some aspects of their feeding habits were studied with special emphasis on the potential impact on the predatorAulonium ruficorne Olivier. A total of 12 predators and 2 parasite species were found associated withA. ruficorne in the natural enemy complex of bark beetles on pines. No secondary parasites were detected. The anthocoridScoloposcelis pulchella (Zetterstedt) and the dipteranMedetera striata Parent were observed feeding on immature stages ofA. ruficorne in the absence of scolytids. The associated Coleoptea:Nemosema elongatum F.,Rhizophagus bipustulatus L.,Corticeus spp.,Plastysoma spp. andPlegaderus discisus Erickson are thought to compete withA. ruficorne on larvae and pupae of bark beetles when the latter are in limited quantities (especially in the lower section of the tree). The parasites, mainlyMetacolus unifasciatuss Forster andDendrosoter caenopachoides Ruschka are assumed to compete withA. ruficorne during the larval period in the smooth bark section of the stem. Competition might occur mainly during spring and fall. Deutonymphs of the miteIpiduropoda sellnicki were detected on the abdomen ofA. ruficorne adults. Larvae of the predator were rarely infected in the field by the bacteriaSerratia sp. while laboratory cultures suffered high rate of mortality caused by this pathogen.      

Ultrastructural study of the microsporidian chytridiopsis typographi (Chytridiopsida: Microspora) infecting the bark beetle,Ips typographus (Scolytidae: Coleoptera), with new data on spore dimorphism

Two types of sporogony of the microsporidian Chytridiopsis typographi in the midgut of adult bark beetle, Ips typographus, have been examined by means of light and electron microscopy. New data are reported on spore dimorphism and on the formation of pansporoblasts in two types of sporogony. Thin-walled spores, larger in size, are formed in a parasitophorous vacuole in the host columnar cells. Thick-walled spores are formed in a minimal vacuole in the host. The ultrastructure of the spore walls and the cyst wall are different from the organization in other microsporidia. Both spore types have identical internal structures and viable spores.     

红脂大小蠹 Dendroctonus valens （ Coleoptera, Scolytidae ）和大唼蜡甲Rhizophagus grandis （Coleoptera, Rhizophagidae）的耐寒性

红脂大小蠹 Dendroctonus valens LeConte (Red turpentine beetle,RTB)是近年来在中国爆发的入侵生物,在我国主要以老熟幼虫在油松伐桩和立木的根部越冬.室内测定昆虫的过冷却点(SCP)和短时间致死低温(LLT)是评价昆虫耐寒能力的重要方法.实验结果显示,红脂大小蠹越冬幼虫的平均过冷却点为一11.98±2.55℃,是一种耐冰冻的昆虫.红脂大小蠹的过冷却点在不同地理分布区的种群问有明显差异,老熟幼虫的过冷却点明显低于低龄幼虫,在越冬前和越冬后的幼虫问没有明显差异.红脂大小蠹幼虫在冬季至少町以忍受-23.5℃的大气温度安全越冬.从2001年开始引入我国的云杉大小蠹的捕食者大唼蜡甲(Rhizophagus grandis cyll.)幼虫的过冷却点为-18.05±2.76℃,低于红脂大小蠹所有虫态的过冷却点,说明比红脂大小蠹有更强的耐寒能力.     

Pathogenicity to western larch (Larix occidentalis) of two fungi, Ophiostoma pseudotsugae and Leptographium abietinum, associated with the Douglas fir beetle (Coleoptera: Scolytidae)

1 Pole-sized, live western larch Larix occidentalis Nutt. were mass-inoculated with Ophiostoma pseudotsugae (Romb.) von Arx or Leptographium abietinum (Peck) Wingf., two blue-stain fungi associated with the Douglas fir beetle Dendroctonus pseudotsugae Hopkins, to assess their pathogenicity. 2 Inoculation with O. pseudotsugae resulted in significantly greater percentages of necrotic phloem compared with L. abietinum inoculations. 3 The percentage of occluded sapwood was significantly greater after L. abietinum inoculations compared with O. pseudotsugae inoculations. 4 Within the inoculation band, all trees had more than 60% functional sapwood 4 months after treatment. 5 The results suggest that western larch can successfully limit colonization by O. pseudotsugae and L. abietinum. 6 The inability of the fungi to thrive in live western larch may be a factor in the consistent failure of Douglas fir beetle broods in this host tree species.