Species of Botryosphaeriaceae associated on mango in Brazil

The aim of the present study was to assess diversity in the Botryosphaeriaceae on trees and fruit of mango (Mangifera indica L.) in a semi-arid region in northeastern Brazil in which most exported fruit in the country are produced. Using morphological characteristics and DNA sequence data (ITS-1, ITS-2 and 5.8S rDNA) we confirmed the presence of Lasiodiplodia theobromae in the region, and for the first time report Fusicoccum aesculi and Neofusicoccum parvum. L. theobromae was prevalent in the Assú Valley and F. aesculi and N. parvum were in the São Francisco Valley. In fruit inoculations, L. theobromae and N. parvum were more virulent than F. aesculi.     

芒果蒂腐病病原葡萄座腔菌科真菌种类鉴定

In order to identify the pathogen of Botryosphaeriaceae causing mango stem-end rot, tissue isolation method was used to process mango samples collected from Hainan, Guangxi, Yunnan, and Sichuan Provinces in China, and 58 fungal isolates were obtained. Among them, 39 isolates were belonged to Botryosphaeriaceae, accounting for 67.24%. These isolates were identified based on morphological characteristics and phylogenetic analysis with internal transcribed spacer (ITS) and elongation factor 1 alpha (EF-1α). The results showed that there were four main species of Botryosphaeriaceae, including Neofusicoccum parvum (33.33%), Lasiodiplodia theobromae (30.77%), Botryosphaeria dothidea (28.21%), and L. pseudotheobromae (7.69%). The mango stem-end rot caused by L. pseudotheobroma was firstly reported in China. The virulence of the four species was tested by in vitro inoculation and the results showed that all isolates were pathogenic, among which L. theobromae, L. pseudotheobroma, and N. parvum were the “strong” grade, and B. dothidea was the “middle” grade.     

Characterization of Botryosphaeriaceae from plantation‐grown Eucalyptus species in South China

The Botryosphaeriaceae is a species‐rich family that includes pathogens of a wide variety of trees, including Eucalyptus species. Symptoms typical of infection by the Botryosphaeriaceae have recently been observed in Eucalyptus plantations in South China. The aim of this study was to identify the Botryosphaeriaceae associated with these symptoms. Isolates were collected from branch cankers and senescent twigs of different Eucalyptus spp. All isolates resembling Botryosphaeriaceae were separated into groups based on conidial morphology. Initial identifications were made using PCR‐RFLP fingerprinting, by digesting the ITS region of the rDNA operon with the restriction enzymes CfoI and KspI. Furthermore, to distinguish isolates in the Neofusicoccum parvum/N. ribis complex, a locus (BotF15) previously shown to define these species, was amplified and restricted with CfoI. Selected isolates were then identified using comparisons of DNA sequence data for the ITS rDNA and translation elongation factor 1‐alpha (TEF‐1α) gene regions. Based on anamorph morphology and DNA sequence comparisons, five species were identified: Lasiodiplodia pseudotheobromae, L. theobromae, Neofusicoccum parvum, N. ribis sensu lato and one undescribed taxon, for which the name Fusicoccum fabicercianum sp. nov. is provided. Isolates of all species gave rise to lesions on the stems of an E. grandis clone in a glasshouse inoculation trial and on the stems of five Eucalyptus genotypes inoculated in the field, where L. pseudotheobromae and L. theobromae were most pathogenic. The five Eucalyptus genotypes differed in their susceptibility to the Botryosphaeriaceae species suggesting that breeding and selection offers opportunity for disease avoidance in the future.     

Detection of Botryosphaeriaceae species within grapevine woody tissues by nested PCR, with particular emphasis on the Neofusicoccum parvum/N. ribis complex

Several species of Botryosphaeriaceae and Phaeomoniella chlamydospora are common agents of grapevine decline worldwide. Currently, the use of culture independent PCR based techniques for detection of Botryosphaeriaceae within grapevine tissues has been limited to Botryosphaeria dothidea. In the present study, two Botryosphaeriaceae specific nested PCR assays were developed. One with a narrow target range, to detect Neofusicoccum parvum and the closely related species complex (Neofusicoccum parvum/N. ribis sensu Pavlic et al. Molecular Phylogenetics and Evolution 51:259–268, 2009) and another, with a wider range, to detect all 17 species of Botryosphaeriaceae which have been reported as potential wood pathogens of grapevine. The effectiveness of these assays was validated in vivo on naturally infected wood samples collected from standing vines and dormant grafted rooted cuttings commercialized in Italy by different nurseries in different years. All samples were also screened by means of a previously published nested PCR assay specific for Phaeomoniella chlamydospora. It was found that: 1) propagation material may play an important role as source of primary inoculum, not only of Phaeomoniella chlamydospora, as previously reported, but also for members of the Botryosphaeriaceae, among which Neofusicoccum parvum, Botryosphaeria dothidea and Diplodia seriata are the most common, and 2) multiple infections by different species belonging to Botryosphaeriaceae and/or Phaeomoniella chlamydospora occur frequently both in standing vines and propagation material. This last finding supports the hypothesis that at least some of the non-specific symptoms of grapevine decline may be due to the presence of different pathogens within host tissues.     

Botryosphaeriaceae species associated with blueberry dieback and sources of primary inoculum in propagation nurseries in New Zealand

Sampling at blueberry farms found Botryosphaeriaceae fungi in five of seven farms sampled; overall incidence was 41.4%, with Neofusicoccum australe (79.0%), N. luteum (8.0%), N. ribis (8.0%) and N. parvum (5.0%). Sampling of nursery plants found infections in all four nurseries with 45% incidence in mainly asymptomatic plants, which were infected with N. australe (66.0%), N. parvum (31.5%) and N. ribis (2.5%). Asymptomatic propagation cuttings from one nursery were found to have external contamination of Botryosphaeriaceae DNA (90.0%) and internal infection (65.0%) by the four main species found in the blueberry farms and nurseries. For propagation media nested PCR showed that out of the 98 samples received, 43 samples were positive for the presence of Botryosphaeriaceae DNA (44.0%). Results from the SSCP indicated that N. australe, N. luteum, N. parvum/ N. ribis and Diplodia mutila were present in the propagation media received. Isolates of the four main species recovered from farms and nurseries were pathogenic on blueberry stems but pathogenicity differed significantly between species and isolates within a species, with N. ribis being the most pathogenic, then N. parvum, N. luteum and N. australe. Overall, the high rate of infection in nursery plants indicated that nurseries can be a major source of infection for blueberry farms. Since propagating cuttings are the likely sources of infection for nurseries, these should be targeted in the control strategies.     

Genetic diversity and population structure of Lasiodiplodia theobromae from different hosts in northeastern Brazil and Mexico

Lasiodiplodia theobromae is one of the most frequent fungal pathogens associated with dieback, gummosis, leaf spot, stem-end rot and fruit rot symptoms in cashew, mango, papaya and grapevine. In this study, the variation in the genetic diversity of 117 L. theobromae isolates from northeastern Brazil (n = 100) and Mexico (n = 17), which were collected from these four crops, was analysed using microsatellite markers. The results revealed low genetic diversity among L. theobromae populations and the existence of two genetic groups. All Mexican isolates were grouped with Brazilian isolates, suggesting a low level of differentiation between these populations. Furthermore, no evident host or climate-based population differentiation was observed for L. theobromae in Brazil. The populations studied were mostly clonal, but additional studies are needed to better understand the mode of reproduction of the pathogen. The low genetic diversity of L. theobromae populations in northeastern Brazil suggests that resistant cultivars could be used as a durable management strategy to reduce the impact of the diseases caused by this pathogen.     

建兰胶孢炭疽菌ITS序列分析及其PCR快速检测

由胶孢炭疽菌Colletotrichum gloeosporioides引起的炭疽病是建兰的重要病害.为建立快速检测该病原菌的方法,以ITSl/ITS4为引物,对15个建兰胶孢炭疽菌的ITS进行PCR扩增及测序,将测定的序列与炭疽菌属其它种的ITS序列进行比对分析,设计特异性引物CFl/CR1,并通过常规和巢式PCR对建兰胶孢炭疽菌进行检测.结果显示,15个菌株中有13个菌株ITS序列与该菌的模式种序列相似性高达99％以上,而另外2个菌株相似性则为86％;供试菌株在系统发育树上聚为2个不同的分支;引物CFl/CR1通过常规PCR可从1 ng的建兰胶孢炭疽菌基因组DNA中扩增到目的条带,而利用引物ITSl/ITS4和CF1/CR1通过巢式PCR可从1 pg的基因组DNA中扩增到目的条带,即巢式PCR反应检测灵敏度较常规PCR至少高1 000倍.表明建立的巢式PCR法可从自然感病的建兰叶片组织中检测到胶孢炭疽菌.     

Differential response to combined prochloraz and thyme oil drench treatment in avocados against the control of anthracnose and stem-end rot

The ability to meet consumers demand for high-quality standard fruit entails the distribution of unblemished safe fruit free of chemical residues on its edible portion. Therefore, this study was focused on investigating the influence of the combined effect of aqueous plant volatiles with half strength prochloraz solution to control anthracnose and stem-end rot in the green-skinned avocado cultivar (Fuerte). This method was applied due to its practicability on bulk fruits in packhouses and the fruits were subjected to stand-alone and combined treatments to assess the development of the disease after cold storage and observe the elicitation of the residual effect of the treatments on the defence related enzymes in ‘Fuerte’. The incidence of stem-end rot was 10% by the combination of prochloraz® (500 μg mL^?1; P50) with 0.1% v/v thyme oil compared to the 58.8% incidence exhibited by the untreated fruit during storage at 6.5 °C for 14 days followed by 3 days at retail shelf conditions (15 °C) (preventative application). Citral (0.1% v/v), P50 (500 μg mL^?1)?+?0.1% v/v citral and yucca extract alone reduced the stem-end rot incidence to about 25% during storage. More so, thyme oil (0.1% v/v) reduced both anthracnose and stem-end rot incidence to 35% after postharvest storage and P50 (500 μg mL^?1)?+?0.1% v/v thyme oil and 0.1% v/v thyme oil effectively induced the activity of phenylalanine ammonia lyase, chitinase and β-1, 3 glucanase in fruit inoculated with Lasiodiplodia theobromae and Colletotrichum gloeosporioides through the improvement of quality and firmness of the fruit after storage.     

Development of isolate‐specific markers for Neofusicoccum parvum and N. luteum and their use to study rainwater splash dispersal in the vineyard

Unique bands were identified in single isolates of Neofusicoccum parvum and Neofusicoccum luteum using universally primed polymerase chain reaction (UP‐PCR) analysis of isolates obtained from grapevines and non‐grapevine hosts in New Zealand, Australia, South Africa and the USA. Primers were designed to amplify a 1550 bp portion of the 1573 bp marker band from N. parvum isolate B2141 and a 510 bp portion of the 524 bp marker band from N. luteum isolate G51a2. A PCR‐RFLP assay was developed to distinguish the N. parvum isolate B2141 from other N. parvum isolates, based on a polymorphism found in the marker band using the TaqI restriction endonuclease. For N. luteum isolate G51a2, the designed primers were specific at an annealing temperature of 63°C in the PCR. The sensitivity threshold of the N. parvum and N. luteum isolate‐specific markers was 50 pg and 5 pg, respectively, when used in standard PCR with purified genomic DNA. The sensitivity of the N. parvum isolate‐specific marker was increased to 0·5 pg by nested PCR. The specificity test of both isolate‐specific markers with six other Botryosphaeriaceae spp. showed that they were specific to their respective species and isolates. Both markers were able to detect the conidia of N. parvum and N. luteum marker isolates in rainwater samples collected at different distances from an inoculation point in the vineyard. The results showed that rain splash could disperse the conidia of both of these species up to 2 m from the inoculum point in a single rainfall event.     

Characterization of Fusarium mangiferae isolates from mango malformation disease in Southern Spain

During the last years, Fusarium strains have been isolated from shoots and inflorescences of mango trees affected with floral and vegetative malformation in different orchards from the Axarquía region (south of Spain), highlighting the identification of Fusarium mangiferae. With the aim of elucidate epidemiological aspects and design more efficient control strategies, population diversity among the strains of F. mangiferae associated with MMD in Spain was determined by ap-PCR, RAPD-PCR, vegetative compatibility groups (VCGs) and mating type analyses. Three different VCGs were found among the Fusarium mangiferae Spanish isolates, two of them showing similar ap–PCR and RAPD profiles. PCR with primers specific for the mating type (MAT) alleles resulted in amplification of the MAT-2 allele fragment among the majority of the isolates, there being only two isolates MAT-1. This population diversity suggests at least three possible independent introductions of the pathogen into the Axarquía region.     

Identification and pathogenicity of Botryosphaeriaceae species associated with root and stem rot of sweet potato in Brazil

The sweet potato (Ipomoea batatas) is characterized by the production of tuberous roots rich in starch and is one of the most produced and consumed vegetables in Brazil. Botryosphaeriaceae, among other fungi, are known to cause root and stem rot of sweet potato. However, no representative and accurate study has been performed for the correct identification of these fungal species in sweet potato in Brazil. Therefore, this study aimed to identify the Botryosphaeriaceae species associated with root and stem rot of sweet potato and confirm their pathogenicity. Tuberous roots and stems of sweet potato with rot symptoms were collected in production fields and markets and used for fungal isolations. The identification of fungi was based on the morphology of reproductive structures and phylogenetic analyses of the gene regions ITS, tef1-α, and rpb2. The following species were identified: Lasiodiplodia theobromae, L. hormozganensis, Macrophomina phaseolina, M. euphorbiicola, M. pseudophaseolina, and Neoscytalidium dimidiatum. For the pathogenicity test, one representative isolate for each species was inoculated in healthy tuberous roots and in 30-day-old healthy seedlings. Black and necrotic lesions on tuberous roots and stems were observed in all replications and resulted in the death of some seedlings. This is the first report of L. hormozganensis, M. pseudophaseolina, and M. euphorbiicola, as causal agents of the stem and root rot of sweet potato and N. dimidiatum as a causal agent of stem rot worldwide.     

云南葡萄产区葡萄炭疽病病原鉴定及致病力分析

为了明确引起云南葡萄产区炭疽病的病原种类,利用形态鉴定和特异性引物分子检测相结合的方法对从云南省主要葡萄产区采集的60株炭疽病菌菌株进行了鉴定。葡萄炭疽病菌菌株的菌落形态和生长速率与对照菌株尖孢炭疽菌Colletotrichum acutatum差异不明显,但其分生孢子大小显著小于尖孢炭疽菌,附着胞深褐色,球形或不规则形。胶孢炭疽菌Colletotrichum gloeosporioides特异性引物CgInt/ITS4从供试葡萄炭疽病菌菌株基因组DNA中扩增出1条约500 bp的特异性条带,而尖孢炭疽菌特异性引物CaInt2/ITS4对葡萄炭疽病菌无扩增条带。研究表明,引起云南葡萄主产区炭疽病的病原为胶孢炭疽菌;供试胶孢炭疽菌对红提葡萄均有致病力,但菌株致病力差异较大,对番茄和草莓存在交叉侵染的能力,且对多菌灵的敏感性较尖孢炭疽菌高。     

The mango sudden decline pathogen, Ceratocystis manginecans, is vectored by Hypocryphalus mangiferae (Coleoptera: Scolytinae) in Oman

In Oman, the bark beetle Hypocryphalus mangiferae is closely associated with trees affected by mango sudden decline disease caused by Ceratocystis manginecans. Although it has previously been assumed that this beetle plays a role in the dispersal of the pathogen, this has not been established experimentally. The aim of this study was to determine whether H. mangiferae vectors C. manginecans from infected to healthy mango trees. A survey conducted in northern Al Batinah region of Oman revealed that H. mangiferae was closely associated with mango sudden decline disease symptoms and it was found on trees in the early stages of the disease. Healthy, 2-year-old mango seedlings were exposed to H. mangiferae collected from diseased mango trees. Seedlings were infested by the bark beetles and after 6 weeks, typical mango sudden decline disease symptoms were observed. Ceratocystis manginecans was isolated from the wilted mango seedlings while uncolonized control seedlings remained healthy. The results show that H. mangiferae vectors C. manginecans in Oman and is, therefore, an important factor in the epidemiology of this disease.     

Inoculum sources of Botryosphaeriaceae species in New Zealand grapevine nurseries

This study investigated the sources of inoculum of Botyosphaeriaceae species in three commercial grapevine nurseries in New Zealand. Botryosphaeriaceae propagules were detected on the surfaces of 33 to 100?% of canes and 33?% of dead grapevine materials using microscopy, plating assays and PCR with Botryosphaeriaceae multi-species primers (Bot100F/Bot472R). Isolations also showed that 15 to 68?% of the canes were internally infected by Botryosphaeriaceae species, with Neofusicoccum luteum and N. parvum being the most predominant species. Incidence varied between nurseries, with Nursery 5 having highest N. luteum incidence (53?%) and Nursery 3 having highest N. parvum incidence (88?%). Botryosphaeriaceae DNA was detected in rain-water run-off from the mother-vine canopy, but not in soil samples collected around infected mother-vines. However, samples from the nursery propagation stages had no visible or viable Botryosphaeriaceae propagules although PCR using multi-species primers detected Botryosphaeriaceae DNA from wash and hydration tanks, on grafting tools and in callusing media from the different nurseries. The single-stranded conformational polymorphism (SSCP) was able to identify N. parvum, N. luteum and Diplodia mutila as the most common species present in the nursery system. Overall results indicated that the canes grown in mother-vine blocks were the most likely source of inoculum for infection of young grafted plants by Botryosphaeriaceae species.     

Diversity of Botryosphaeriaceae causing grapevine trunk diseases and their spatial distribution under different climatic conditions in Algeria

The family Botryosphaeriaceae is one of the most widespread and cosmopolitan endophytic group of fungi. Every year, species of this family cause severe damages on table and wine grape production, worldwide. However, this threat is still poorly known in Algeria. In this study, a large number of Botryosphaeriaceae-like isolates were obtained from symptomatic grapevines collected from eight regions with different ecological conditions, namely: Boumerdès, Médéa, Algiers, Tipaza, El Taref, Sidi Bel Abbes, Biskra and Adrar. The isolates were identified using DNA sequences of the translation elongation factor (tef1-α) and internal transcribed spacer (ITS) regions. Eleven species belonging to six genera, including Neofusicoccum parvum, N. algeriense, N. vitifusiforme, N. stellenboschiana, N. luteum, Diplodia seriata, D. olivarum, Lasiodiplodia theobromae, Dothiorella sarmentorum, Botryosphaeria dothidea and Neoscytalidium dimidiatum were identified. The spatial distribution of the Botryosphaeriaceae showed that D. seriata and N. stellenboschiana were the most widespread in the Algerian vineyards, while L. theobromae was recorded in the desert region of Biskra. Pathogenicity trials showed that all species were pathogenic on detached green shoots of grapevine, with N. parvum and L. theobromae being the most aggressive.

     

Susceptibility of grapevine pruning wounds to infection by Lasiodiplodia theobromae and Neofusicoccum parvum

The susceptibility of 1‐ and 2‐year‐old grapevine wood to botryosphaeria canker caused by Lasiodiplodia theobromae and Neofusicoccum parvum was evaluated in California in two seasons. In the 2007 dormant season, pruning‐wound susceptibility was highest when wounds were inoculated immediately after pruning in December (80% of pruning wounds were infected in Chardonnay for both fungal species and 75% and 98% in Cabernet Sauvignon for N. parvum and L. theobromae, respectively). In the 2008 dormant season, pruning‐wound susceptibility was highest in November in Chardonnay (86% and 93% for N. parvum and L. theobromae, respectively) and in December in Cabernet Sauvignon (71% and 75% for N. parvum and L. theobromae, respectively). The lowest infection rates (13–35%) were observed when vines were pruned and inoculated in March in both dormant seasons and for both cultivars. Susceptibility of pruning wounds did not differ significantly (P = 0·7612) between 1‐ and 2‐year‐old wood and consequently, pruning‐wound protection treatments should be applied to all wounds. In conclusion, grapevine pruning wounds were susceptible to infection by L. theobromae and N. parvum to varying extents throughout the dormant season in California (November–March), but, overall, susceptibility of pruning wounds was highest when inoculations were done immediately after pruning and decreased significantly as the interval between pruning and inoculation increased. Results of this study suggest that pruning grapevines in late winter (March) in California would significantly reduce the risk of infection by L. theobromae and N. parvum.     

Characterization of Lasiodiplodia species causing leaf blight,stem rot and fruit rot of fig (Ficus carica) in Malaysia

Fig (Ficus carica) is an exotic deciduous plant that is grown worldwide. Fungal diseases pose a major threat to fig plants, affecting their fruit quality and production. This study was conducted to characterize the fungal isolates associated with leaf blight, stem rot and fruit rot of F. carica in Malaysia through morphological analysis, DNA sequencing, multigene phylogenetic analysis and pathogenicity tests. From September 2018 to March 2019, 30 blighted leaves and 30 rotted stems and fruits of F. carica were collected from several nurseries in Malaysia. Thirty fungal isolates that belonged to Lasiodiplodia theobromae (27 isolates) and L. brasiliensis (three isolates) were identified based on morphological characteristics, comparison of DNA sequences and phylogenetic analysis of the internal transcribed spacer (ITS), elongation translation factor 1-α (tef1-α), β-tubulin (tub2) and DNA-directed RNA polymerase II subunit (rpb2). Among the 27 isolates of L. theobromae, nine isolates were obtained from leaves, eight isolates from stems and 10 isolates from fruits, whereas the three isolates of L. brasiliensis were obtained from stems (two isolates) and a leaf (one isolate). The results of pathogenicity tests revealed that L. theobromae and L. brasiliensis isolates were responsible for leaf blight and stem rot of F. carica, whereas fruit rot was caused by L. theobromae isolates. The present study highlighted two different species, L. theobromae and L. brasiliensis, as the causal agents of leaf blight and stem rot of F. carica. Additionally, L. theobromae caused fruit rot of F. carica in Malaysia.     

Development of a real-time fluorescence loop-mediated isothermal amplification assay for rapid and quantitative detection of Fusarium mangiferae associated with mango malformation

Fusarium mangiferae is a major causal agent of mango malformation disease (MMD) worldwide. Rapid and accurate detection of the causal pathogen is the cornerstone of integrated disease management. In this paper, a real-time fluorescence loop-mediated isothermal amplification assay (RealAmp) was developed for quantitative detection of F. mangiferae in China. The LAMP primer set was designed based on a RAPD marker sequence and positive products were amplified only from F. mangiferae isolates, but not from any other species tested, showing a high specificity of the primer sets. The detection limit was approximately 2.26 × 10⁻⁴ ng/μl plasmid DNA when mixed with extracted mango DNA. Quantification of the pathogen DNA of MMD in naturally collected samples was no significant difference compared to classic real-time PCR Additionally, RealAmp assay was visual with an improved closed-tube visual detection system making the assay more convenient in diagnostics.     

Botryosphaeriaceae species causing dieback on Annonaceae in Brazil

In Brazil, the Annonaceae species Annona muricata, A. squamosa, A. cherimola and atemoya (a hybrid of A. cherimola and A. squamosa) are cultivated in several regions, and produce fruits that are highly appreciated by consumers and are of great economic importance. Among the several diseases that can affect these crops, dieback is one of the most important, causing damage and, in the most severe cases, death of the plants. Due to the lack of suitable diagnostic studies up to now, this work aimed to identify the Botryosphaeriaceae species that cause dieback on Annonaceae in Brazil. Based on combined phylogenetic analyses of ITS, TEF-1α, TUB2 and RPB2, eight species of Botryosphaeriaceae were identified, namely Lasiodiplodia brasiliense, L. crassispora, L. hormozganensis, L. iraniensis, L. pseudotheobromae, L. subglobosa, L. theobromae and Pseudofusicoccum stromaticum. All species found in this study were pathogenic and caused symptoms of necrosis in stems and dieback. Thus, this study confirms species of Botryosphaeriaceae as causal agents of dieback on Annonaceae in Brazil.     

Aetiology and causal agents of mango sudden decline disease in the Sultanate of Oman

Mango sudden decline is a recently introduced, economically serious disease in Oman. Affected mango trees have wilting symptoms that usually begin on one side and later spread to involve the entire tree. Trees exude amber-coloured gum from the bark of their trunks or branches and vascular tissues are discoloured. Having entered Oman in the recent past, survey data is presented that shows the disease to have spread throughout the northern part of the country. Evidence is presented that the vascular wilt pathogen Ceratocystis fimbriata causes mango sudden decline disease in Oman, possibly in concert with Lasiodiplodia theobromae and the recently described Ceratocystis omanensis. Isolates of these fungi from affected trees, cause infection and can be recovered from inoculated seedlings. Bark beetles (Hypocryphalus mangiferae) are shown to carry C. fimbriata and L. theobromae and are presumably responsible for transmitting both pathogens to healthy mango trees. Acting as a wounding agent and vector, the bark beetle is likely to have assisted the rapid spread of the disease across Oman.