Isolation and virulence of entomopathogenic fungi against the great spruce bark beetle,Dendroctonus micans (Kugelann) (Coleoptera: Scolytidae)

Twelve fungal strains including Lecanicillium muscarium (Petch.) Zare and Gams, Isaria farinosa (Holmsk.) Fr., Fusarium sp., Beauveria bassiana Sensu Lato and Beauveria sp. were isolated from larvae and adults of D. micans. In addition, virulence of these isolates against this pest was determined. Conidia suspensions of 1×10⁶ conidia mL^–1 were applied to larvae and adults. The highest mortality and mycosis for larvae were obtained from isolate ARSEF 9271 (Beauveria bassiana) with 90% mortality and mycosis within 10 days. ARSEF 9271 also produced 93% mortality and mycosis in adults. On the other hand, the highest mortality and mycosis for adults were obtained with isolate ARSEF 9272 (Beauveria sp.), with 100% mortality and 80% mycosis within 10 days. These results indicate that isolates ARSEF 9271 and ARSEF 9272 seem to be the most promising potential fungal biocontrol agents against D. micans.     

Screening of entomopathogenic fungi against 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 destructive pests of oriental spruce (Picea orientalis L.). In order to find an effective biocontrol agent against this pest, we determined the effectiveness of entomopathogenic fungi against D. micans. Virulence of nine highly pathogenic strains including Beauveria bassiana (2), Beauveria cf. bassiana (2), Metarhizium anisopliae (2), Metarhizium sp. (1), Isaria fumosorosea (1) and Evlachovaea sp. (1) was evaluated on D. micans larvae and adults under laboratory conditions. Mortality values for both larvae and adults ranged from 83 to 100% and from 23 to 100%, respectively. Larvae were more susceptible to fungi than adults (P<0.05). Based on screening tests, B. cf. bassiana isolate KTU-53 was found the most effective isolate. LC₅₀ values were calculated as 1.77×10⁴ and 2.65×10⁴ conidia mL^?1 for isolate KTU-53 against larvae and adults, respectively. Consequently, B. cf. bassiana isolate KTU-53 appears to be the most promising microbial control agent for biocontrol of D. micans.     

Isolation and characterization of 16 microsatellite loci in the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae)

We isolated 16 polymorphic microsatellite loci in the mountain pine beetle (Dendroctonus ponderosae Hopkins) and developed conditions for amplifying these markers in four multiplex reactions. Three to 14 alleles were detected per locus across two sampled populations. Observed and expected heterozygosities ranged from 0.000 to 0.902 and from 0.100 to 0.830, respectively. Three loci deviated from Hardy-Weinberg equilibrium in one sampled population. One of these loci may be sex linked. These markers will be useful in the study of population structure in this important pest species.     

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.     

红脂大小蠹后肠挥发性物质的鉴定、触角电位和室内趋向实验

对外来松树害虫红脂大小蠹Dendroctonus valens LeConte的信息化学物质进行了研究。通过GC-MS测定,鉴定出红脂大小蠹后肠挥发性物质中除了含有松树挥发性物质α-蒎烯、β-蒎烯、3-蒈烯、月桂烯和柠檬烯外,还含有马鞭草烯醇和马鞭草烯酮;利用触角电位技术,对马鞭草烯醇、马鞭草烯酮以及在林间引诱效果最好的3-(+)-蒈烯进行了触角电生理测试;利用Y-型双向选择嗅觉仪对这些物质进行了室内趋向实验。实验结果表明: 1 μg的马鞭草烯醇、马鞭草烯酮和3-(+）-蒈烯引起雌雄触角的电位反应分别达416 μV/470 μV、597 μV/630 μV和926 μV/1 099 μV。浓度为1 μL/mL的马鞭草烯酮引起红脂大小蠹的正趋向反应,而在100 μL/mL浓度下引起红脂大小蠹的负趋向反应;在1 μL/mL的浓度下,3-(+ )-蒈烯引起了红脂大小蠹正趋向反应,而马鞭草烯醇则对红脂大小蠹具有驱避作用,说明这些物质在红脂大小蠹搜寻寄主和调节虫口密度方面起着重要作用。     

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.     

外来入侵害虫红脂大小蠹对寄主挥发物的反应

2002年,利用寄主挥发性物质(+)-α-蒎烯、(-)-β-蒎烯、3-蒈烯和(-)柠檬烯按不同配比制成诱芯,采用自行研制的挥发物释放装置,在山西省关帝山森林经营局西葫芦林场对危害油松Pinus tabulaeformis Carr.的重大外来入侵林业害虫红脂大小蠹Dendroctomus valens LeConte进行了引诱试验。结果表明,3蒈烯对红脂大小蠹的引诱作用最强,明显优于单独使用(+)-α-蒎烯和(-)-β-蒎烯的诱虫效果,也比北美应用的标准诱芯［(+)- α蒎烯(-)-β-蒎烯与3-蒈烯的比例为1∶1∶1］效果好;在标准诱芯中加入油松另一主要成分-(-)柠檬烯会明显降低诱虫效果。红脂大小蠹引诱剂最佳释放量为150 mg/d。该研究不仅对我国红脂大小蠹的监控具有实际应用意义,也从理论上探讨了红脂大小蠹与寄主油松协同进化的化学生态学过程。     

Cost-effectiveness analysis of options within an Integrated Crop Management regime against great spruce bark beetle, Dendroctonus micans, Kug. (Coleoptera: Scolytidae)

1 Great spruce bark beetle Dendroctonus micans (Kug.) (Coleoptera: Scolytidae) has been subject to an Integrated Crop Management (ICM) regime in Great Britain since its first discovery in 1982. The elements of the ICM approach are sanitation felling of the initial infestations, restriction on movement of potentially infested conifers to prevent spread to uninfested parts of the country and biological control through rearing and release of the specific predatory beetle Rhizophagus grandis Gyll. (Coleoptera: Rhizophagidae). Such a programme carries costs that have to be evaluated against the benefits to the ICM strategy. 2 This paper presents a cost-effectiveness analysis of three options – (i) continue with the current policy of restriction on movement of infested timber and use of the imported predator R. grandis, (ii) do nothing (i.e. drop all attempts to reduce the spread of D. micans), or, (iii) introduce a new east–west Dendroctonus Micans Control Area (DMCA) to define the management area. Assumptions on rates of mortality and natural spread were based on research into D. micans in Britain’s spruce forests. 3 Appraisal indicated that the current policy was the most cost-effective, even when subject to sensitivity analysis to test the limits of the assumptions included in the models. It is concluded that the current policy should remain in force.     

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.     

Metabolism and cold tolerance of Chinese white pine beetle Dendroctonus armandi (Coleoptera: Curculionidae: Scolytinae) during the overwintering period

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Feeding behaviour of the black pine beetle,Hylastes ater (Coleoptera: Scolytidae)

1 The feeding behaviour of Hylastes ater was investigated at 15 °C and 20 °C on a range of tree species. The role of an aggregation pheromone and the part played by olfactory cues in food selection was also investigated. 2 A distinct hierarchical preference at both 15 °C and 20 °C such that Pinus radiata > Pinus sylvestris > > Picea abies > > Rubus fruticosus=Betula pendula was shown. 3 Feeding on P. sylvestris led to the highest weight gain, closely followed by P. radiata and P. abies. Slightly elevated feeding was observed at 20 °C compared with 15 °C. 4 Reduced feeding in the presence of B. pendula suggests the possibility of an antifeedant effect and predamaged wood was found to be less nutritious, possibly due to greater plant defences. 5 The role of an aggregation pheromone was not supported. Olfactory cues enabled the detection of woody hosts, although differentiation between host was not observed. 6 These results are likely to be important in helping to design an effective integrated control approach against this pest.     

Effects of cold stress on metabolic regulation in the overwintering larvae of the Chinese white pine beetle,Dendroctonus armandi

The Chinese white pine beetle, Dendroctonus armandi Tsai & Li (Coleoptera: Curculionidae, Scolytinae), is considered the most destructive forest pest in the Qinling and Bashan Mountains of China. In recent years, winter temperature has dropped in these regions, and extremely low temperatures are hard to survive for insects. Cold hardiness becomes a crucial strategy because temperature change often leads to fluctuations in insect abundance, and the metabolism rate is a key index of resistance to cold in overwintering insects. Therefore, we investigated the relationship between the change in respiratory rate and the activity of metabolism-related mitochondrial enzymes in D. armandi larvae under cold conditions. We found that the respiratory rate decreased, and it was matched with the activity of glutamate dehydrogenase, aconitase, and lipase during overwintering. Among the various test times under cold conditions, the respiratory rate also decreased with decreasing temperature and increased under very low temperatures. At all cold stress periods, glutamate dehydrogenase and lipase showed increased activity at higher temperatures and decreased activity under lower temperatures, but the activity of NAD-malic enzyme, NADP-malic enzyme, mitochondrial isocitrate dehydrogenase, and aconitase were contrary. Under all low temperatures, the activity of enzymes – except for NADP-malic enzyme, glutamate dehydrogenase, and lipase – increased in short-term cold stress and decreased in long-term cold stress at 4, 0, −4, −6, −8, and −10 °C. However, at −2 °C, the activity of enzymes showed a decreasing trend in short-term treatments and an increasing trend in long-term treatments, except for mitochondrial isocitrate dehydrogenase. The results not only improve our understanding of the metabolic mechanism of cold adaptation in D. armandi, but also provide an important experimental basis for further study and biological pest control.     

Phylogeography of the bark beetle Dendroctonus mexicanus Hopkins (Coleoptera: Curculionidae: Scolytinae)

Dendroctonus mexicanus is polyphagous within the Pinus genus and has a wide geographical distribution in Mexico and Guatemala. We examined the pattern of genetic variation across the range of this species to explore its demographic history and its phylogeographic pattern. Analysis of the mtDNA sequences of 173 individuals from 25 Mexican populations allowed to us identify 53 geographically structured haplotypes. High haplotype and low nucleotide diversities and Tajima’s D indicate that D. mexicanus experienced rapid population expansion during its dispersal across mountain systems within its current range. The nested clade phylogeographic analysis indicates that the phylogeographic pattern of D. mexicanus is explained by continuous dispersion among lineages from the Sierra Madre Occidental, the Sierra Madre Oriental and the Trans-Mexican Volcanic Belt. However, we also observed isolation events among haplotypes from the Cofre de Perote/Trans-Mexican Volcanic Belt/Sierra Madre Oriental and the Trans-Mexican Volcanic Belt/Sierra Madre del Sur, which is consistent with the present conformation of mountain systems in Mexico and the emergence of geographical barriers during the Pleistocene.     

华山松大小蠹及其伴生蓝变真菌对华山松木质部危害的解剖学特征

为揭示华山松大小蠹和伴生蓝变真菌引起秦岭华山松枯萎的机制,选择秦岭北坡沣峪林场境35年树龄的健康华山松Pinus armandi为研究对象,对接种华山松大小蠹Dendroctonus armandi及与其伴生的蓝变真菌Ceratocystis polonica引起的寄主树木木质部形态变化进行了解剖观察。结果表明：接种致病性蓝变真菌C. polonica 1周后的4株华山松 的木质部组织内,蓝变区域显著增加,4～6周后蓝变区域不再增加; 而在接种无菌琼脂的2株对照华山松的木质部组织内,没有检测到蓝变区域。研究结果提示蓝变真菌C. polonica是致死秦岭华山松的重要病原菌,该伴生菌随华山松大小蠹入侵健康寄主华山松木质部组织,在木质部定居并分解木质部,堵塞树脂道,致使寄主华山松树脂代谢和水分代谢紊乱。该研究结果表明,虽然华山松大小蠹长期以来被认为是致死华山松的毁灭性小蠹虫,但是其共生蓝变真菌C. polonica对成熟华山松的致害作用不应该被忽视。     

Development of an improved attractive lure for the pine shoot beetle, Tomicus piniperda (Coleoptera: Scolytidae)

Abstract 1 The pine shoot beetle, Tomicus piniperda (L.) (Coleoptera: Scolytidae), is an exotic pest of pine, Pinus spp., and was first discovered in North America in 1992. 2 Although primary attraction to host volatiles has been clearly demonstrated for T. piniperda, the existence and role of secondary attraction to insect‐produced pheromones have been widely debated. 3 Currently, commercial lures for T. piniperda include only the host volatiles α‐pinene in North America and α‐pinene, terpinolene and (+)‐3‐carene in Europe. Several potential pheromone candidates have been identified for T. piniperda. 4 We tested various combinations of host volatiles and pheromone candidates in Michigan, U.S.A., and Ontario, Canada, to determine an optimal blend. 5 Attraction of T. piniperda was significantly increased when trans‐verbenol (95% pure, 3.2%cis‐verbenol content) was added with or without myrtenol to α‐pinene or to blends of α‐pinene and other kairomones and pheromone candidates. 6 Our results, together with other research demonstrating that trans‐verbenol is produced by T. piniperda, support the designation of trans‐verbenol as a pheromone for T. piniperda. A simple operational lure consisting of α‐pinene and trans‐verbenol is recommended for optimal attraction of T. piniperda.     

Nonhost angiosperm volatiles and verbenone disrupt response of western pine beetle, Dendroctonus brevicomis (Coleoptera: Scolytidae), to attractant-baited traps

Nonhost angiosperm volatiles and verbenone were tested for their ability to disrupt the response of western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Scolytidae), to attractant-baited multiple funnel traps. Verbenone significantly reduced attraction; however, no difference was observed between 4 and 50 mg/24-h release rates. Combinations of six bark volatiles (benzyl alcohol, benzaldehyde, trans-conophthorin, guaiacol, nonanal, and salicylaldehyde), three green leaf volatiles [(E)-2-hexenal, (E)-2-hexen-1-ol, and (Z)-2-hexen-1-ol], and the nine compounds combined did not significantly reduce D. brevicomis response to attractant-baited traps. However, a significant effect was observed when the bark and green leaf volatiles were combined with verbenone. The nine nonhost angiosperm volatiles (NAVs) significantly augmented the effect of both release rates of verbenone, reducing trap catches to levels significantly below that of either release rate of verbenone alone. trans-Conophthorin, a compound reported to have behavioral activity in a number of other scolytids, was not critical to the efficacy of our NAV blend. Our results suggest that the addition of nonhost angiosperm volatiles to verbenone could be important for developing successful semiochemical-based management techniques for D. brevicomis.     

Reproductive isolation and environmental adaptation shape the phylogeography of mountain pine beetle (Dendroctonus ponderosae)

Chromosomal rearrangement can be an important mechanism driving population differentiation and incipient speciation. In the mountain pine beetle (MPB, Dendroctonus ponderosae), deletions on the Y chromosome that are polymorphic among populations are associated with reproductive incompatibility. Here, we used RAD sequencing across the entire MPB range in western North America to reveal the extent of the phylogeographic differences between Y haplotypes compared to autosomal and X‐linked loci. Clustering and geneflow analyses revealed three distinct Y haplogroups geographically positioned within and on either side of the Great Basin Desert. Despite close geographic proximity between populations on the boundaries of each Y haplogroup, there was extremely low Y haplogroup mixing among populations, and gene flow on the autosomes was reduced across Y haplogroup boundaries. These results are consistent with a previous study suggesting that independent degradation of a recently evolved neo‐Y chromosome in previously isolated populations causes male sterility or inviability among Y haplotype lineages. Phylogeographic results supported historic contraction of MPB into three separate Pleistocene glacial refugia followed by postglacial range expansion and secondary contact. Distinct sets of SNPs were statistically associated with environmental data among the most genetically distinct sets of geographic populations. This finding suggests that the process of adaptation to local climatic conditions is influenced by population genetic structure, with evidence for largely independent evolution in the most genetically isolated Y haplogroup.     

Attraction of the southern pine beetle, Dendroctonus frontalis, to pheromone components of the western pine beetle, Dendroctonus brevicomis (Coleoptera: Curculionidae: Scolytinae), in an allopatric zone

Subtle differences in pheromone components of sympatric species should be attractive only to the producing species and unattractive or repellent to the nonproducing species, and thereby maintain reproductive isolation and reduce competition between species. Bark beetles Dendroctonus brevicomis and D. frontalis (Coleoptera: Curculionidae) are known to have common pheromone components, except for exo-brevicomin, which is produced by D. brevicomis. We predicted that D. frontalis would not respond to exo-brevicomin outside of the zone of sympatry with D. brevicomis. We conducted a field experiment to determine the effect of exo-brevicomin on attraction of D. frontalis and associated species in Mississippi. We determined whether D. frontalis pheromone production differed inside and outside the sympatric zone and compared the pheromone profiles with D. brevicomis within the sympatric zone. Trapping studies revealed that D. frontalis can perceive and respond positively to exo-brevicomin, an aggregation pheromone of a sympatric congener (D. brevicomis), at locations hundreds of kilometers outside the sympatric zone. Qualitative pheromone profiles showed that both species emit similar pheromone components: frontalin, endo-brevicomin, exo-brevicomin, trans-verbenol, verbenone, and myrtenol. Although not previously reported, D. frontalis males from Arizona produced exo-brevicomin. The predator Thanasimus dubius did not discriminate traps baited with exo-brevicomin and was most attracted to traps with frontalin. Hylastes beetles were significantly attracted to traps baited with exo-brevicomin in combination with other compounds. Our results raise new practical and evolutionary questions on the role of exo-brevicomin in the behavioral ecology of D. frontalis. The addition of exo-brevicomin to the current lure might increase the efficiency of trapping programs in the southeastern United States.