Lateral transfer of a phytopathogenic symbiont among native and exotic ambrosia beetles

Different ambrosia beetle species can coexist in tree trunks, where their immature stages feed upon symbiotic fungi. Although most ambrosia beetles are not primary pests and their fungal symbionts are not pathogenic to the host tree, exceptional situations exist. Notably, Xyleborus glabratus carries a phytopathogenic symbiont, Raffaelea lauricola, which causes laurel wilt, a lethal disease of some Lauraceae species. Both X. glabratus and R. lauricola are natives of Asia that recently invaded much of the coastal plain of the southeastern USA. This study examined ambrosia beetles that breed in susceptible trees in Florida (USA), including avocado (Persea americana), redbay (P. borbonia) and swampbay (P. palustris). Raffaelea lauricola was recovered from six of eight ambrosia beetle species that emerged from laurel wilt‐affected swampbay trees, in addition to X. glabratus. Controlled infestations with cohorts of the six species other than X. glabratus revealed that each could transmit the pathogen to healthy redbay trees and two could transmit the pathogen to healthy avocado trees; laurel wilt developed in five and one of the respective beetle × host interactions. These results indicate flexibility in the lateral transfer of a non‐native ambrosial fungus to other ambrosia beetles, and for the first time documents the transmission of a laterally transferred phytopathogenic symbiont by new ambrosia beetle species. Additional work is needed to determine whether, or to what extent, the new beetle × R. lauricola combinations play a role in spreading laurel wilt.     

Sudden Oak Death, A New Forest Disease in California

A forest disease caused by a newly described pathogen, Phytophthora ramorum, is presently affecting a number of woody plant species in central and northern coastal California and southern Oregon, U.S.A. Among the most severely affected tree species are coast live oak, Quercus agrifolia, and tanoak, Lithocarpus densiflorus. In March 2000, we established plots in Marin County, CA, to assess symptom progression and the association of other organisms with diseased trees. Symptomatic trees exhibit 'bleeding' of viscous sap from apparently intact bark, typically within approximately 2 m of the soil. At least three species of bark and ambrosia beetles colonize bleeding oaks. These beetles colonized every bleeding tree that died during the first year of the study (N = 23) while the foliage was still green. By March 2001, numbers of symptomatic and dead trees increased for both coast live oak and tanoak. Symptomatic coast live oaks totaled 26% in March 2000 and 27% in March 2001. During the same period, mortality increased from 6% to 10%. For tanoaks, 41% were symptomatic in 2000, rising to 49% in 2001. Mortality was 11% in 2000 and 13% in 2001. The values for coast live oak are broadly consistent with independently acquired infection and mortality estimates derived from an unbiased transect method.     

Potential for Nonhost Volatiles as Repellents in Integrated Pest Management of Ambrosia Beetles

Semiochemical-based mass trapping of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae), has been the cornerstone of an integrated pest management (IPM) programme for ambrosia beetles on the British Columbia coast since 1981. However, there is no available tactic of protecting logs from attack that could be incorporated into the IPM programme. We tested nonhost volatiles (NHVs) from the bark of angiosperm trees for their ability to disrupt catches of T. lineatum in multiple-funnel traps baited with the aggregation pheromone lineatin. In one set of experiments, a blend of 1-hexanol and benzyl alcohol caused 77.9% and 80.0% reduction in captures of males and females, respectively, and in another a blend of methyl salicylate and salicylaldehyde caused reductions of 65.0% for males and 66.9% for females. All four NHVs combined caused reductions in captures for males and females of 82.3% and 81.4%, respectively, not much greater than to the blend of 1-hexanol and benzyl alcohol. However, because both blends were active alone, their redundancy when combined lends confidence to the selection of the four-component blend for operational testing. Although disruption was increased when a 16-component NHV blend was tested, or when (±)–(E)-conophthorin was added to the four-component blend, addition of more compounds to the four-component blend was not considered operationally or economically justifiable. When deployed from low-density polyethylene tubes stapled along the length of pheromone-baited conifer logs, this blend caused prolonged and significant reductions in landing by T. lineatum and also by Gnathotrichus sulcatus (LeConte) and G. retusus (LeConte) (Coleoptera: Scolytidae). However, attacking beetles generally overcame the NHV treatment by the end of the flight period, leading to similar attack densities on treated and control logs. Therefore, we recommend that further operational investigations explore using repellent NHVs in combination with disruptive visual, tactile or gustatory stimuli.     

Anoplophora glabripennis infestation (col.: cerambycidae) in Italy

In June 2007, the Asian longhorned beetle Anoplophora glabripennis (Motschulsky) was found at Corbetta, in Lombardy, 23 km west of Milan, Italy. The invasive exotic pest was observed in four host trees, one sycamore maple Acer pseudoplatanus L. and three silver birches Betula pendula Rothmahler. During summer 2007, 20 living and 107 dead A. glabripennis beetles were collected on or around the infested trees. The dissection of the infested material showed that 287 beetles emerged from the trees during previous years and 158 living larvae of varied ages were still developing in April, 2008. Fortunately, it appears that predation by birds on early stage larvae developing under the bark, played a major role in limiting the developing pest population. A. glabripennis is native to China and Korea where it is considered as a serious pest of many deciduous trees including maples, poplars, and willows. During the last decade, it was accidentally introduced into the USA, Canada, Austria, Germany and France in wood packaging material of goods imported from China. The current discovery in Italy is the first record of the Asian pest in this country.     

Report of a pest risk analysis for Platypus parallelus (Fabricus, 1801) for Turkey

Invasive bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) are increasingly responsible for damage to forests, plantations and orchards worldwide. They are usually closely associated with fungi, which may be pathogenic causing tree mortality. Stressed or weakened trees are particularly subject to attack, as is recently felled, non‐treated wood. This PRA report concerns the ambrosia beetle Platypus parallelus (Euplatypus parallelus, Fabricus, 1801) (Coleoptera: Scolytidae), which was detected in official controls. The PRA area is Turkey. P. parallelus is not on the A1 or A2 list for Turkey but the Regulation on Plant Quarantine (3 December 2011‐OJ no: 28131) Article 13 (5) indicates that pests which are assessed to pose a risk for Turkey following PRA that are not present in the above lists and plants, wood, plant products and other materials contaminated by these organisms are banned from entry into Turkey. This risk assessment follows the EPPO Standard PM 5/3(5) Decision‐support scheme for quarantine pests and uses the terminology defined in ISPM 5 Glossary of Phytosanitary Terms. This paper addresses the possible risk factors caused by Platypus parallelus (Euplatypus parallelus, Fabricus, 1801) in Turkey.     

Spatial Distribution of Ambrosia-Beetle Catches: A Possibly Useful Knowledge to Improve Mass-Trapping

Several species of ambrosia beetles (Coleoptera: Scolytidae) have recently started attacking standing, living beeches (Fagus sylvatica) in southern Belgium. In 2001, 1.3 million m³ of apparently healthy trees were struck. So far the outbreak has been limited to the Ardenne, and partly the Gaume, areas, and Brussels has been untouched. The city of Brussels is surrounded by a vast 4300 ha forest, mainly planted with beech, the Forêt de Soignes, of invaluable ecological and recreational value, of which 1600 ha belong to the regional authorities. In the spring 2001, these latter commissionned a study to assess the new threat to the forest. A 500 m×500 m grid of small traps, baited with ethanol and lineatin, was deployed over the regional part of the forest. The main species caught were Trypodendron domesticum, Anisandrus dispar and, in high numbers, Xylosandrus germanus, an exotic species of Asian origin found for the first time in Belgium in 1994. Whilst there was a consistent homogeneity between catches within the same sites (2 traps/site, distant by 2–6 m), there were no spatial relationships between catches at larger distances for T. domesticum and A. dispar. For X. germanus, spatial autocorrelations were observed within distances of 2000 m, suggesting that this species has sufficient mobility to cover this range. The planning of the 2002 trapping campaign will take this information into account: the traps will be deployed within a smaller grid.     

Beetles (Coleoptera) caught with pheromones of Gnathotrichus retusus and G. sulcatus (Col., Scolytidae) in southern Finland

The ambrosia beetle Gnathotrichus materiarius, which originally came from North America, was discovered in southern Finland in 1996. In 1997, using Norwegian drainpipe traps baited with pheromones of Gnathotrichus retusus and G. sulcatus, we collected beetles in the region where the first specimen had been caught in order to determine whether this potential pest species had become established in the area. Samples from a total of 16 traps included 79 species of beetles and 719 individuals, but no specimens of G. materiarius. The most abundant species in the samples were the ambrosia beetles Xyleborus dispar and Trypodendron lineatum. Several predators and other associates of bark beetles were also captured. The majority of the beetles caught were saproxylic species.     

Beetles (Coleoptera) caught with pheromones of Gnathotrichus retusus and G. sulcatus (Col., Scolytidae) in southern Finland

The ambrosia beetle Gnathotrichus materiarius, which originally came from North America, was discovered in southern Finland in 1996. In 1997, using Norwegian drainpipe traps baited with pheromones of Gnathotrichus retusus and G. sulcatus, we collected beetles in the region where the first specimen had been caught in order to determine whether this potential pest species had become established in the area. Samples from a total of 16 traps included 79 species of beetles and 719 individuals, but no specimens of G. materiarius. The most abundant species in the samples were the ambrosia beetles Xyleborus dispar and Trypodendron lineatum. Several predators and other associates of bark beetles were also captured. The majority of the beetles caught were saproxylic species.     

林业小蠹类昆虫在中国的适生性分析综合比较研究

小蠹类昆虫是重要的林业害虫类群,严重威胁我国的林业生产和生态安全,具有重要的经济意义。综合比较中国林业小蠹类昆虫的适生性分析方法,有助于把握林业小蠹类昆虫物种分布模型的研究动向。该文归纳整理中国林业小蠹类昆虫的适生性分析文献,统计文献所使用的模型、适生性等级划分标准以及文献来源等信息,并对小蠹类昆虫适生性分析未来发展进行展望,以期为林业有害生物防控提供参考。     

天山野果林塞威士苹果和短距凤仙花叶斑病病原真菌的鉴定

为了解新疆天山野果林中塞威士苹果Malus sieversii与其林下伴生植物短距凤仙花Impatiens brachycentra两种植物叶斑病病原菌的多样性及同源性,采用组织分离法获得病原菌,基于rDNA-ITS序列构建系统发育树,并进行ITS序列BLAST同源性比对,对病原菌进行鉴定分类,并依据科赫氏法则测定致病性。结果显示,从新疆新源县天山野果林中的塞威士苹果及短距凤仙花病叶上共分离得到18株菌落形态各异的病原菌,分属于2属4种,绝大多数属于半知菌亚门。其中,链格孢属Alternaria sp.为塞威士苹果和短距凤仙花叶斑病病原真菌中的优势菌群。致病性测定结果显示,其中11株病原真菌对塞威士苹果具有致病性,7株病原真菌对短距凤仙花具有致病性;塞威士苹果所有的病原真菌对短距凤仙花均有致病性,而且短距凤仙花所有的病原真菌对塞威士苹果也有致病性。推测2种植物叶斑病可能由相同来源的病原真菌引发,短距凤仙花染病加剧了塞威士苹果叶斑病暴发,可能是野果林退化的重要原因。     

Potential distribution ranges in Europe for Ips hauseri, Ips subelongatus and Scolytus morawitzi, a CLIMEX analysis

Introduced bark and ambrosia beetles have become a worldwide problem for the forest industry as well as for recreational parks and nature reserves by directly damaging wood material and killing trees or by vectoring lethal tree diseases. In this study we used the climatic modeling program CLIMEX to simulate potential distribution ranges for three different Asian bark beetles, Ips hauseri (Reitter), Ips subelongatus (Motschulsky) and Scolytus morawitzi (Semenov) on the basis of their current distribution. The program calculates an ecoclimatic index based on the life cycle requirements of a species and thus represents the probability of a viable population existing at a certain location. Simulations show that all of the studied species have a potential distribution according to climatic factors. Also, potential hosts for these species grow in much of Europe, making the potential establishment of these species possible. Simulation with the Intergovernmental Panel on Climate Change (IPCC) climate change scenario A1B resulted in changes of 200 to 900 km at the northern and southern edges of the distribution ranges for the studied species.     

First record of ambrosia beetle (Euplatypus parallelus) infestation on cashew from Goa, India

The occurrence of ambrosia beetle Euplatypus parallelus (Fabricius) (Coleoptera: Curculioninae: Platypodinae) infestation on cashew (Anacardium occidentale L.) is reported for the first time from Goa, India. Most of the infested trees were either previously attacked by cashew stem and root borer Plocaederus ferrugineus (Coleoptera: Cerambycidae) or were pruned trees. The visible symptoms of attack include appearance of numerous round bore holes on the tree trunk and branches, and extrusion of fibrous dust frass on the tree trunk and in loose piles at the base of the tree. Large numbers of larvae, pupae and adults were observed in the galleries of the affected trees. Adult beetles measure 4.0–4.3 mm in length and are brown in color, having long and slender bodies with yellow hairs. They have a characteristic feature of absence of pores on the pronotum. Male and female insects were identified based on the elytral declivity.     

Diversity and pathogenicity of the Ceratocystidaceae associated with cacao agroforests in Cameroon

Knowledge of the diversity and ecology of plant pathogenic fungi in cacao agroforests and surrounding natural ecosystems can inform the development of sustainable management strategies for new cacao disease outbreaks. This study investigated the occurrence of fungi related to the Ceratocystidaceae and their nitidulid beetle vectors in cacao agroforests in Cameroon, under diverse agroecological conditions. The fungi and their vectors were collected from artificially induced stem wounds on cacao and associated shade trees. Collections were also made from abandoned cacao pod husks and other tree wounds within and around plantations. Fungal isolates were identified using DNA sequence‐based phylogenies and morphological comparisons, and two representatives of each species were evaluated for pathogenicity on cacao. Five species of Ceratocystidaceae were recovered, including Huntiella chlamydoformis sp. nov., H. pycnanthi sp. nov. and H. moniliformis, as well as Thielaviopsis cerberus and T. ethacetica. The incidence of these fungi appeared to be influenced by the prevailing agroecological conditions. Nitidulid beetles in the genus Brachypeplus were found to be their most common insect associates on cacao. Both T. ethacetica and H. pycnanthi produced extensive lesions after inoculation on branches of mature cacao trees, while T. ethacetica also caused pod rot. Although their impact remains unknown, fungi in the Ceratocystidaceae and their nitidulid beetle vectors are common and probably contribute to the parasitic pressure in Cameroonian cacao agrosystems.     

Note:In vitro antagonism of actinomycetes isolated from fungus-growing ants against plant pathogenic fungi

Fungus-growing ants have been found recently to be symbiotic with actinomycetes living on the ant’s cuticle; these bacteria are inhibitory to soil fungi that are detrimental to the ants’ fungus gardens. In order to investigate whether actinomycetes found on the cuticle of attine ants also had inhibitory properties against plant pathogenic fungi, we isolated 32 strains of actinomycetes from fungus-growing ants (Atta, Trachymyrmex, andCyphomyrmex), from the Mexican states of Coahuila, Nuevo León and Tamaulipas. Of the actinomycetes tested against selected plant pathogenic fungi (Alternaria solani, Aspergillus flavus, Colletotrichum lindemuthianum, Rhizoctonia solani, Sclerotium sp.) on Czapek-Dox agar medium, 13 isolates inhibited at least one of the fungi.C. lindemuthianum was inhibited by 11 actinomycetes, andRhizoctonia by three. An actinomycete strain isolated fromCyphomyrmex rimosus inhibited all five fungi tested. http://www.phytoparasitica.org posting July 30, 2008.     

Pathogenicity of four blue-stain fungi associated with aggressive and nonaggressive bark beetles

ABSTRACT The pathogenicity of two isolates of each of four bark beetle-associated blue-stain fungi was evaluated after mass inoculation of about 40-year-old Norway spruce trees (Picea abies). Trees were inoculated with a different isolate of each fungus in 1995 and 1996 at a density of 400 inoculations per m(2) in a 1.2-m-wide band on the lower bole (about 270 inoculations per tree). Trees were felled 15 weeks after inoculation. In 1995, Ceratocystis polonica was the only fungus that had stained the sapwood (56.3% of cross-sectional sapwood area). It induced five times longer phloem necroses, 21 times more dead cambium, and 11 times more dead phloem than any other fungus. In 1996, C. polonica induced less extensive host symptoms and an unidentified Ambrosiella sp. induced comparable symptoms to C. polonica in the phloem and cambium. No trees showed any foliar symptoms 15 weeks after inoculation, but six out of eight trees inoculated with C. polonica in 1995 had only 0 to 25% functional sapwood and probably would have died if felling had been delayed. This study confirms that C. polonica, an associate of the aggressive bark beetle Ips typographus, is pathogenic to Norway spruce. The pathogenicity of the Ambrosiella sp., which is associated with a nonaggressive bark beetle, seems moderate and varies between isolates. The two remaining fungi included in this study (Ophiostoma piceae and a dark fungus with sterile mycelium), which are associated with nonaggressive bark beetles, were nonpathogenic in both experiments. These results are consistent with the hypothesis that aggressive bark beetle species vector virulent fungi that may help them kill trees, but the results also show that some nonaggressive bark beetles may vector phytopathogenic fungi.     

Bacterial community associated with the ambrosia beetle Platypus cylindrus on declining Quercus suber trees in the Alentejo region of Portugal

In Portugal, the oak pinhole borer Platypus cylindrus and its mycobiota have been associated with cork oak (Quercus suber) death, but no knowledge exists regarding the associated bacterial community. However, it is known that some bacteria are important for ambrosia beetle symbiosis and play a role in oak tree health. To explore the bacteria associated with this beetle and its host, with the ultimate goal of highlighting potential roles in oak decline, this study used a culture-dependent approach for strain isolation and phylogenetic identification using 16S rRNA gene sequencing and multilocus sequence analysis (MLSA). The bored galleries of different cork oak trees from a cork stand in Alentejo, together with the body and mycangia of adult beetles, were investigated. The samples revealed a diverse community comprising 500 isolates with 64 distinct types of bacterial colonies. Sixty-eight strains were selected for sequencing and used for phylogenetic analysis, 40 from wood galleries and 28 from beetles. Thirty-two genera of bacteria were identified, 18 of which were described for the first time within oak–beetle interactions. Major taxonomic groups were Actinobacteria in beetles and Enterobacterales in wood galleries. Although specific oak bacterial pathogens were not detected, a group of distinct strains detected in wood galleries, potentially belonging to a new Pectobacteriaceae species, were able to produce mild symptoms on cork oak plantlets. This study reports for the first time the biodiversity of culturable bacteria associated with the Q. suber–P. cylindrus interaction, their relevance to both organisms and the possible contribution to oak decline.     

Death of endemic Virgilia oroboides trees in South Africa caused by Diaporthe virgiliae sp. nov.

Numerous dead and dying individuals of the Western Cape endemic tree Virgilia oroboides (Fabaceae) were recently observed within a South African national botanical garden. Root‐rot fungi and fungi symbiotic with bark beetles (Curculionidae; Scolytinae) from diseased trees were assessed for their respective roles in V. oroboides mortality. Disease progression was also monitored over 1 year. Fungi were isolated from surface sterilized bark and root samples from diseased trees and provisionally identified using data from the internal transcribed spacer regions (ITS1, ITS2), including the 5·8S rRNA gene (ITS). Pathogenicity of selected fungi towards V. oroboides was tested under field conditions. The pathogenicity of various bark beetle‐associated Geosmithia (Hypocreales: Hypocreomycetidae) spp. from V. oroboides were similarly assessed. The only fungus consistently isolated from lesions on the roots and bark of declining V. oroboides, and never from healthy individuals, represented an undescribed Diaporthe (Diaporthales, Diaporthaceae) species that was characterized using molecular (using data from the ITS marker and part of the β‐tubulin gene, TUB), cultural and morphological characters. It is an aggressive pathogen of V. oroboides, newly described here as Diaporthe virgiliae sp. nov. Trees of all ages are susceptible to this pathogen with subsequent bark beetle attack of mature trees only. All Geosmithia spp. from beetles and/or infected trees were nonpathogenic towards V. oroboides. Diaporthe virgiliae caused a severe decline in the health of the monitored V. oroboides population over a period of only 1 year and should be considered as a significant threat to these trees.     

Einige ?kologische Aspekte der Ambrosiasymbiose

Die Ambrosia-Symbiose zwischen holzbrütenden Scolytiden und Platypodiden hat zu weitgehenden Anapassungen beider Partner geführt. Ambrosiapilze sind in ihrer Toleranz gegenüber klimatischen Bedingungen weitgehend eingeschränkt und in ihrer Verbreitung auf den Insektensymbionten angewiesen, während die Käfer in ihrer Ernährung von den Symbionten abhängig sind. Ein spezielles Organ, das Mycetangium, wurde zur Erhaltung der Pilzflora außerhalb der Brutanlagen entwikkelt. Dieses Organ entstand polyphyletisch in den versichiedenen systematischen Einheiten. Die Symbiose ist in den Familien Scolytidae und Platypodidae und deren Untereinheiten mehrfach unabhängig voneinander entzanden. Die Reareaktionen auf die unterschiedlichen ökologischen Gegebenheiten sind daher sehr variabel.In many ambrosia beetles (wood boring Scolytidae and all Platypodidae) a special fungus transmitting organ, the mycetangium, ensures fungus survival during hibernation and/or flight as well as the inoculation of new galleries. Fatty nutritional and probably selective sheltering fluids are secreted by holocrinous gland cells connected with the mycetangium during the growth of funguis inside this organ and only then. Consequently, tolerance levels of true ambrosia fungi towards climatic conditions are narrowed down compared with other auxiliary or free blue stain fungi. Survival and proparation is dependent on the insect partner, while the ambrosia beetles depend on their microsymbionts for their nutrition. The ambrosia symbiosis has developed independently in the differen axonomic groups. Adaptations to the different ecological requisitions of the beetle results in a great variability of symbiotic patterns.

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Meiner verehrten Lehrerin, Frau Prof. Dr.H. Francke-Grosmann in dankbarem Gedenken     

进口植物及植物产品有害生物风险分析

本文从经济、生态和人及人类社会3个方面阐述了外来有害生物的风险;根据国际标准中制订的有害生物风险分析流程,定性地描述了有害生物风险分析的方法;并从入侵种特性研究、适生区预测研究和风险分析模型3个方面阐述了有关有害生物风险分析的理论研究进展,这些理论研究有助于为有害生物风险定量分析提供科学依据。     

Pathogenic and Genetic Diversity of Soilborne Isolates of Cylindrocladium from Banana Cropping Systems

Pathogenicity and genetic variation were investigated within a collection of 104 banana-infecting isolates of Cylindrocladium (teleomorph Calonectria) originating from different countries and representing previously described morphological taxa or species. These root-rot fungi, along with endoparasitic nematodes, have been reported to be causal agents of necrotic lesions that induce root breakage and toppling of banana plants. Little is known about the individual pathogenic effects of the species involved or their genetic diversity. In the present study, among the five morphological taxa found in the banana rhizosphere, only isolates showing an atypical morphology relative to Cylindrocladium gracile (named Cy. gracile-like isolates) and Cy. spathiphylli isolates were pathogenic on banana cultivar Grande Naine. When comparing the latter isolates with others of the same species, but originating from different hosts, an analysis of rDNA spacer polymorphism partitioned isolates of Cy. spathiphylli by host into a banana – tea group and a Heliconia – Spathiphyllum group. Furthermore, isolates from Heliconia were not pathogenic on banana. A pathogenicity assessment of representative isolates from the Cy. gracile-like and the Cy. spathiphylli taxa on six different banana cultivars yielded no evidence of differential interactions between isolates and banana genotypes. Significant differences in susceptibility between banana genotypes were nevertheless detected that could potentially be exploited by breeders. Random amplified polymorphic DNA analysis revealed a genetic similarity ranging from 70% to 100% within Cy. spathiphylli isolates from bananas regardless of the geographic origin. Moreover, Cy. gracile-like isolates were highly similar but showed only 60% similarity relative to the Cy. gracile reference isolates, thus raising questions about their species status.