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。     

外来入侵林业害虫强大小蠹的侵袭以及相关信息化学物质

强大小蠹是入侵我国并造成很大危害的鞘翅目棘胫小蠹科大小蠹属树皮低干森林害虫。它能侵害多种针叶树和松树 ,能被寄主挥发物和其它小蠹虫的外激素所引诱。该文综述了强大小蠹的侵袭习性以及寄主挥发物、其它小蠹虫的外激素对强大小蠹的引诱和驱避作用。     

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。     

7种松树挥发物分析及其主要萜烯类物质对红脂大小蠹行为选择的影响

入侵种红脂大小蠹在我国逐渐向北扩散至内蒙古和辽宁等地.同时在林间发现,相对于油松Pinus tabuliformis,其更偏好危害樟子松Pinus sylvestris var.mongolica.本文主要分析我国7种松树挥发性物质以及新发生地红脂大小蠹对其中主要物质的行为选择.本研究采用动态顶空采样法和气相色谱——质谱联用技术(GC-MS),对7种松树树干木段挥发性有机化合物(VOCs)进行采集和分析,包括油松、樟子松、华山松Pinus armandii、白皮松Pinus bungeana、马尾松 Pinus massoniana、红松 Pinus koraiensis和落叶松 Larix gmelinii.在此基础上参考以往研究中与红脂大小蠹行为相关的化合物,选择树种挥发物中7种主要烯烃类化合物:(1R)-(+)-α-蒎烯、(+)-3-蒈烯、(-)-β-蒎烯、月桂烯、(S)-(-)-柠檬烯,萜品油烯和莰烯,通过自制十通道行为仪器进行嗅觉反应试验,分析红脂大小蠹在不同浓度的化合物刺激下的行为选择反应.GC-MS结果表明,7种松树树干释放化合物中共包含烯烃类、醇类、酮类、醛类、酯类、酸类、烷烃和芳香烃8类化合物在内的54种化合物,其中烯烃类化合物相对含量最高.主成分分析及聚类分析结果表明,红脂大小蠹以往偏好寄主油松与新偏好寄主樟子松的挥发物相似度最高,(+)-3-蒈烯为其特有的挥发性物质,莰烯含量高于其他树种;4种受害寄主树种(油松、樟子松、白皮松和华山松)挥发性物质相似,均含有高比例的α-蒎烯,同时有β-蒎烯、柠檬烯、萜品油烯.选择上述6种化合物及月桂烯(华山松、白皮松中共有的萜烯类化合物)进行行为选择反应.结果显示,受害寄主树种中含有β-蒎烯以及油松、樟子松中的特征性挥发物质(+)-3-蒈烯对雌虫具有明显的吸引作用,低浓度(-)-柠檬烯(10-4mg/mL)对雄虫具有吸引作用;低浓度(10-4mg/mL)月桂烯对雌虫以及中浓度(10-2mg/mL)莰烯对雌雄成虫具有刺激性.综上所述,本研究证明了红脂大小蠹的寄主选择行为趋性与寄主树干挥发物的组成和含量有关.本试验结果将有助于理解植物挥发物对红脂大小蠹偏好寄主选择的影响,并进一步开发红脂大小蠹的引诱剂和趋避剂以应用于其防治.     

三种松树内生真菌的分离鉴定及其对红脂大小蠹伴生真菌的拮抗作用

【背景】松树的内生真菌会影响红脂大小蠹及其伴生真菌的生长及扩散,从而影响红脂大小蠹的入侵。【目的】掌握赤峰地区红脂大小蠹寄主树种内生真菌的物种多样性,筛选对其伴生菌有拮抗作用的菌株,为红脂大小蠹的生物防治提供资源。【方法】采用组织分离法、形态学鉴定和internal transcribed spacer (ITS)序列分析相结合的方法对红脂大小蠹寄主树种油松、樟子松和潜在寄主落叶松进行内生真菌多样性研究,并用两点对峙法进行拮抗菌株筛选。【结果】松树内生真菌鉴定为2门6纲10目18科19属,其中落叶松韧皮部分离到的内生真菌数量最多,为39株,隶属于9属12种,真菌检出率为43.33%;油松次之,为30株,隶属于7属8种,真菌检出率为33.33%;樟子松最少,为29株,隶属于10属13种,真菌检出率为32.22%。3个树种的内生真菌相似性较低,无共有的菌种,青霉属(Penicillium)和篮状菌属(Talaromyces)是唯二的共有菌属,且青霉属在3个树种中均为优势菌属。平板对峙结果表明90%以上的树木内生真菌均能够与伴生真菌形成稳定的对峙,抑制率在50%-86%之间,且Phialocephala sp.和Pochonia bulbillosa对伴生菌的抑制率能高达93.7%。【结论】松树韧皮部的内生真菌具有较高的生防潜力,Phialocephala sp.和P. bulbillosa对红脂大小蠹伴生菌有较好的抑制效果,可作为红脂大小蠹的生防资源。     

一种红脂大小蠹天敌切头郭公虫Clerus sp.生物学初探

红脂大小蠹Dendroctonus valens LeConte,原产于北美,于20世纪80年代随木材贸易传入我国山西,是一种危害油松、白皮松、华山松等松科植物的毁灭性入侵害虫。本文对红脂大小蠹天敌切头郭公甲虫Clerus sp.的基本生物学特征进行了初步探讨。野外诱捕发现,红脂大小蠹诱剂3-蒈烯能诱捕到切头郭公甲虫Clerus sp.,并观察到此郭公甲虫紧抱红脂大小蠹的捕食行为及红脂大小蠹头部被切下的残骸。诱捕动态监测表明切头郭公甲虫与红脂大小蠹的发生在时间和数量上具有跟随关系。室内测定结果显示切头郭公甲虫平均体重约15.5 mg且个体大小与捕食能力呈正相关。切头郭公虫平均存活时间约38 d,10 d内平均每头郭公虫捕食3头红脂大小蠹,最多达8头。行为嗅觉试验表明切头郭公虫Clerus sp.对红脂大小蠹诱芯反应敏感,红脂大小蠹信息素组分frontalin不能增加其对红脂大小蠹诱芯的敏感性。本研究初步探明了红脂大小蠹天敌切头郭公虫Clerus sp.生物学特征,其较长捕食周期和较强的捕食能力决定其可作为红脂大小蠹的生物防治因子具有一定的优势和较好的天敌应用前景。     

华山松大小蠹共生真菌对华山松木质部危害的解剖学研究

通过对野外和人工接种条件下,华山松大小蠹（Dendroctonus armandi)共生直菌（Leptographium terebrantis)对寄主华山松木质部危害的解剖学研究。结果表明,华山松大小蠹共生真菌随华山松大小蠹入侵健康寄主华山松木质部组织,真菌菌丝首先在其木质部树脂道内发育,分解木质部树脂道泌脂细胞,堵塞树脂道;通过菌丝在木质部交叉场薄壁细胞内及管胞细胞间和管胞细胞内的扩展,使寄主华山松树脂代谢,抗性物质代谢和水分代谢紊乱,木质部边材组织蓝变。     

外来入侵种红脂大小蠹COⅠ基因分化的研究

红脂大小蠹Dendroctonu svalens LeConte为近年来危害最为严重的外来入侵生物。本研究利用特异引物扩增出红脂大小蠹COⅠ基因序列(GenBank登录号:GQ495096-GQ495128),在160个位点中发现3个该种与大小蠹属其他种不同的特异位点;比较不同地理种群的红脂大小蠹,发现中国种群间遗传分化不明显,说明入侵种的瓶颈效应,而遗传变异是入侵种与环境长期互作的结果;基于COⅠ基因序列比对的研究发现,入侵中国的红脂大小蠹与该虫原发生地北美洲部分种群具有同源性。     

黑里河地区红脂大小蠹出孔与降落位置的研究

【目的】明确红脂大小蠹Dendroctonus valens羽化出孔位置及受吸引时的降落位置,为监测和诱捕等防治技术提供理论依据。【方法】在内蒙古自治区黑里河国家级自然保护区,通过对受害油松的干基部及周边地面进行分区采集,统计红脂大小蠹的出孔位置;统计扬飞期受引诱剂吸引的红脂大小蠹的降落位置。【结果】红脂大小蠹多在寄主树木根部越冬,成虫出蛰伏后咬破根皮向上挖穿土层到达地表;受害树干基及周围地表不同区域出孔的红脂大小蠹比例存在极显著差异（P<0.001）。在距受害树干基0-50 cm的地表区域内捕获的红脂大小蠹最多,占79.90%±16.99%,其次为距受害树干基50-100 cm的区域,捕获比例为17.77%±14.12%,在树干上捕获的红脂大小蠹的比例较低。明确了红脂大小蠹寻找寄主时的降落位置,在不同区域的降落比例具有极显著差异（P<0.001）。在树干距地表0-50 cm高处降落的红脂大小蠹最多,占比为41.09%±4.25%,其次是树干50-100 cm的区域,占27.47%±4.31%,此外树干100-150 cm的区域、地面距干基0-150 cm范围内也均有红脂大小蠹降落。【结论】在黑里河地区,红脂大小蠹多在根部越冬,翌年多在距干基0-50 cm的地表区域内出孔并扩散。在使用熏蒸法防治时,建议以受害树为中心覆盖50 cm的地面,如有条件可覆盖到距干基100 cm;红脂大小蠹在寻找寄主时,多降落在树干距地面0-50 cm的高度,建议在较低的高度悬挂诱捕器。     

外来入侵种入侵机制研究取得的新进展

<正>入侵种的入侵机制是入侵生物学的核心科学问题。已有假说主要从天敌、资源和生态位几方面阐述了入侵种的入侵性。但是现有的入侵理论只能解释部分入侵物种的入侵性,所以新的入侵理论令人期待。2006年至今,动物研究所孙江华研究员领导的森林害虫化学生态研究组以红脂大小蠹-伴生真菌为研究模型,以多物种协同作用为切入点,开展了红脂大小蠹入侵机制的研究,继2007年     

红脂大小蠹传入中国危害特性的变化

通过对山西省灵空山林场与北京小龙门林场的红脂大小蠹危害情况进行详细调查,运用生态位理论对红脂大小蠹选择入侵不同树势油松进行分析,同时查阅陕西、山西、河北、北京等地红脂大小蠹危害的多年历史资料,以此来探讨红脂大小蠹传入中国后危害特性的变化。结果表明：红脂大小蠹传入中国后已由最初危害衰弱木和受伤木的次期性害虫变异为主要危害健康木和轻度衰弱木的初期性害虫,从而为揭示其种群扩张过程、灾害发生机制以及采取相应的控制措施提供了重要的理论依据。     

Mutual interactions between an invasive bark beetle and its associated fungi

Interactions between invasive insects and their fungal associates have important effects on the behavior, reproductive success, population dynamics and evolution of the organisms involved. The red turpentine beetle (RTB), Dendroctonus valens LeConte (Coleoptera: Scolytinae), an invasive forest pest in China, is closely associated with fungi. By carrying fungi on specialized structures in the exoskeleton, RTB inoculates fungi in the phloem of pines (when females dig galleries for egg laying and when males join them for mating). After eggs hatch, larvae gregariously feed on the phloem colonized by the fungi. We examined the effects of five isolates of RTB associated fungi (two from North America, Leptographium terebrantis and L. procerum, and three from China, Ophiostoma minus, L. sinoprocerum and L. procerum) on larval feeding activity, development and mortality. We also studied the effects of volatile chemicals produced in the beetle hindgut on fungal growth. Ophiostoma minus impaired feeding activity and reduced weight in RTB larvae. Leptographium sinoprocerum, L. terebrantis and L. procerum did not dramatically influence larval feeding and development compared to fungi-free controls. Larval mortality was not influenced by any of the tested fungi. Hindgut volatiles of RTB larvae, verbenol, myrtenol and myrtenal, inhibited growth rate of all the fungi. Our results not only show that D. valens associated fungus, O. minus, can be detrimental to its larvae; but, most importantly, they also show that these notorious beetles have an outstanding adaptive response evidenced by the ability to produce volatiles that inhibit growth of harmful fungus.     

The red turpentine beetle, <Emphasis Type="Italic">Dendroctonus valens</Emphasis> LeConte (Scolytidae): an exotic invasive pest of pine in China

An exotic invasive pest of pines, the red turpentine beetle, Dendroctonus valens LeConte (Scolytidae) (RTB), was first detected in Shanxi Province, northern China, in 1998 and started causing widespread tree mortality there in 1999. This outbreak continues and has spread to three adjacent provinces, causing unprecedented tree mortality. Although it is considered a minor pest of pines in North America, RTB has proven to be an aggressive and destructive pest of Pinus tabuliformis, China’s most widely planted pine species. The bionomics and occurrence, distribution, response to host volatiles, and host preference of this pine beetle in China are compared with what is known of the beetle in its native range in North America. Factors likely contributing to D. valens success in China and control of the beetle outbreak are discussed. (−)-β-pinene was shown to be the most attractive host volatile for D. valens from the Sierra Nevada of California, whereas 3-(+)-carene is the most attractive host volatile for beetles in China. Monocultures of Pinus tabuliformis, several consecutive years of drought conditions and warm winters have apparently factored D. valens invasion and establishment in China.     

Host tree resistance influencing pheromone production in Ips typographus (Coleoptera: Scolytidae)

Analyses of volatiles in hindguts of Ips typgraphus males from different spruce trees and attack phases are reviewed. The composition of monoterpenes, and the chirality of α-pinene, have been determined in phloem samples. Relationships between compounds emanating from spruce trees and bark beetles, respectively, have been studied. Male beetles depend on their host tree for the production of pinene alcohols. The ratio between the pinene alcohols is almost constant in males boring in the same tree but can vary widely between males from different spruce trees. Very good correlations were found between some host tree monoterpene hydrocarbons and bark beetle produced pinene alcohols. The production of the essential pheromone component 2-methyl-3-buten-2-ol, was not correlated with the monoterpene content in the host trees, while the production of the other essential pheromone component, cis-verbenol, depends on the amount of the precursor, (−)-α-pinene in the phloem. Male beetles boring in a resistant spruce tree will continue to produce the pinene alcohols, including cis -verbenol, as long as the tree defends itself with resin.     

Population genetics and symbiont assemblages support opposing invasion scenarios for the red turpentine beetle (Dendroctonus valens)

Exotic forest insects and their symbionts pose an increasing threat to forest health. This is apparently true for the red turpentine beetle (Dendroctonus valens), which was unintentionally introduced to China, where the beetle has killed millions of healthy native pine trees. Previous population genetics studies that used cytochrome oxidase I as a marker concluded that the source of D. valens in China was western North America. In contrast, surveys of fungi associated with D. valens demonstrated that more fungal species are shared between China and eastern North America than between China and western North America, suggesting that the source population of D. valens could be eastern North America. In this study, we used microsatellite markers to determine population structure of D. valens in North America as well as the source population of the beetle in China. The analyses revealed that four genetically distinct populations (herein named the West, Central, Northeast and Mexico) represent the native range of D. valens. Clustering analyses and a simulation‐based approximate Bayesian computation (ABC) approach supported the hypothesis that western North America is the source of the invasive D. valens population. This study provides a demonstration of non‐congruence between patterns inferred by studies on population genetics and symbiont assemblages in an invasive bark beetle.     

The effects of α‐pinene on the feeding performance and pheromone production of Dendroctonus valens

Herbivorous insects exploit multiple plant cues to detect and orient toward suitable hosts and, accordingly, hosts have evolved complex constitutive and inducible defenses in response. In China, the red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Curculionidae: Scolytinae), an invasive bark beetle from North America, attacks mainly Pinus tabuliformis Carrière (Pinaceae), which contains many monoterpenes. In this study, we explored how the monoterpene α‐pinene affects the feeding performance and pheromone production of D. valens. First, the composition and quantities of monoterpenes of both P. tabuliformis healthy trees and fresh stumps were determined and the infestation of D. valens in healthy trees and fresh stumps was investigated, linking the amount of monoterpenes and D. valens infestation. Gas chromatography–mass spectrometry (GC‐MS) analysis showed that P. tabuliformis mainly contained α‐pinene, with concentrations of 0.1 and 0.5 mg g^?1 in healthy pine phloem and stump phloem, respectively. Second, the monoterpene's influence on feeding performance was tested using phloem media with α‐pinene concentrations ranging from 0 to 30 mg g^?1. The results showed that the percentages of beetles boring and the gallery lengths of both adult females and larvae were negatively correlated with the α‐pinene concentration although body weight changes did not correlate with α‐pinene concentration. Finally, pheromone analysis showed that the production of all pheromones increased with increasing α‐pinene concentrations. This study showed the dual effects of α‐pinene on D. valens: α‐pinene inhibited the bark beetle's feeding activities and in turn the bark beetle made use of it to produce pheromones. Our study indicated the importance of promptly removing fresh stumps in the field for the management of the bark beetle.     

Fungal,host and non-host volatiles modify attraction of the walnut twig beetle,Pityophthorus juglandis,to pheromone lures

1. Thousand Cankers Disease (TCD) of walnut trees is caused by the pathogenic fungus Geosmithia morbida vectored by the walnut twig beetle (WTB) Pityophthorus juglandis. Monitoring efforts for WTB rely on pheromone-baited traps, but lures are likely effective at attracting beetles only over short distances. Fungal-derived kairomones may increase the efficacy of current lures, while additional volatiles may repel beetles from valuable trees.
2. The objective of this study was to determine the extent to which fungal, host and non-host volatiles modify the attraction of WTB to pheromone-baited traps. A trapping study that combined fungal, host-associated and non-host compounds with WTB-pheromone lures was conducted over three years in black walnut plantations experiencing a TCD outbreak in Walla Walla, WA.
3. Traps baited with pheromone and G. morbida volatiles (i.e., isoamyl and isobutyl alcohol) consistently attracted more WTB, while other fungal volatiles inconsistently increased attraction compared to those baited with pheromone lure alone. This is the first field study that demonstrates fungal volatiles can increase the attraction of a bark beetle to its pheromone in a hardwood system.
4. One fungal (benzyl alcohol) and two additional volatiles (limonene, piperitone) repelled WTB from pheromone-baited traps. Although limonene is known to repel WTB, this is the first demonstration that benzyl alcohol and piperitone repel a bark beetle.
5. Fungal volatiles may increase the efficacy of monitoring efforts and may play an important role in management tactics for WTB, especially in detecting the introduction and establishment of nascent populations and protecting trees from colonizing beetles.

     

Large Shift in Symbiont Assemblage in the Invasive Red Turpentine Beetle

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