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Examples of ambrosia beetles and their frass associated with ROD. (A) Ambrosia beetle frass accumulating on the outer bark of an ʻōhiʻa tree, (B) Xyleborus ferrugineus excavating a gallery in ROD-infected ʻōhiʻa, (C) emergence chambers for beetle rearing, and (D) ambrosia beetle gallery extending throughout the surface area of a Ceratocystis-infected ʻōhiʻa cookie. Photo (B) by J.B. Friday, University of Hawaiʻi at Mānoa.
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Rapid ʻŌhiʻa Death (ROD) is a deadly disease that is threatening the native Hawaiian keystone tree species, ʻōhiʻa lehua (Metrosideros polymorpha Gaudich). Ambrosia beetles (Curculionidae: Scolytinae) and their frass are hypothesized to play a major role in the spread of ROD, although their ecological niches and frass production within trees and ac...
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... not yet fully understood, the dissemination of the pathogens from infected trees is hypothesized to be at least partially facilitated by ambrosia beetles (Curculionidae: Scolytinae) and their frass or boring dust (i.e., wood particles, feces, and beetle parts; Fig. 1A) Keith 2018, Roy et al. ...
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... case of Xyleborus glabratus and laurel wilt disease, a single founding female established a population that has killed over 320 million trees in the southeastern United States ( Hughes et al. 2017). The potential for indirect movement of pathogens embedded in frass that is produced and expelled during gallery excavation is not well understood (Fig. 1B). Dislodged frass particles containing pathogens can be transported by soil, wind, and/or water, and ultimately inoculate an otherwise healthy tree by entering through a wound (Harrington ...
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... 64-, 102-L) Tough Storage Totes, HDX (The Home Depot, Atlanta, GA) with screened holes for ventilation on the lids and connected by a 3-in (76-mm) diameter hole to a 1-quart (0.946-L) regular mouth Ball (Ball Corporation, Broomfield, CO) mason jar. Mason jars contained moistened paper towels that were replaced as needed (i.e., dried out, molding) (Fig. 1C). Boring Dust Traps (BDT), designed to collect frass and emerging beetles ( Roy et al. 2019), were attached to the entrances of frass-producing beetle galleries and ranged from 0 to 16 BDT per bolt section (N = 178). Emerging beetles were collected from both the mason jars and BDT at least once per week and identified to species using ...
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... gallery system and any material extruded into the environment by the larvae would also include frass of adults ( Hosking 1973, Biedermann et al. 2012). Instead, viability may be dependent on fungal growth at the excavation location, particularly because galleries of Xyleborini beetles often extend through both the sapwood and heartwood of trees ( Fig. 1D; Hosking 1973, Samuelson and Gressit 1976, Roeper et al. 1980, Peer and Taborsky 2007, Misra et al. 2020, although further investigation is necessary. Hughes et al. (2020) recently found that C. lukuohia can penetrate the heartwood of ʻōhiʻa, further increasing the potential for beetles to contact the fungus during gallery ...
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... The nature of the interactions between the two organisms in hickory requires further investigation. The presence of C. huliohia and/ or C. lukuohia in the frass of five ambrosia beetle species (Subtribe Xyleborina) has been documented (Roy et al., 2020) and the pathogens have been detected in airborne frass particles (Atkinson et al., 2019;Heller et al., 2023). Frass collected from the outer bark of C. lukuohia-killed trees was found to be pathogenic to ʻōhiʻa seedlings when introduced to stem wounds in growth chamber studies (Hughes et al., 2023). ...
Both Ceratocystis lukuohia and C. huliohia have been associated with Rapid ʻŌhiʻa Death(ROD), an emerging threat to ʻōhiʻa (Metrosideros polymorpha), a keystone forest tree species. The vascular wilt disease caused by C. lukuohia has been recently described and is responsible for the widespread ROD epidemic on Hawai'i Island. However, the role of C. huliohia in ROD development and tree death is not clear. Artificial inoculation of field-grown ʻōhiʻa with C. huliohia and dissections of naturally infected, early symptomatic forest trees were conducted to confirm pathogenicity on field grown trees and the pattern of internal colonization. In two trials, crowns of trees with main stems inoculated with C. huliohia were visually healthy at the time of tree harvest after 43–55 days in the first trial, and after 91 days in the second trial. However, elliptical inner bark cankers underlain by reddish-brown xylem were associated with the inoculation points. Similar canker and stain symptoms were found on stems and branches of ʻōhiʻa (24–26 cm trunk diameter) naturally infected by C. huliohia. This xylem stain manifested as multiple distinct elliptical cankers or the coalescing of multiple cankers. The pathogen was commonly isolated from the perimeter of the stained outer sapwood and to a depth of 4 cm. The coalescence of multiple cankers was associated with the crown symptoms observed on the naturally infected forest trees that were dissected. Multiple C. huliohia infections that lead to coalescing cankers which subsequently
girdle stems likely occurs over one or more years compared to the shorter
time (e.g., months) required for C. lukuohia-caused death to occur.
... More recently, ' ohi'a trees are being killed across large areas by fungal disease caused by two introduced pathogens, Ceratocystis lukuohia and Ceratocystis huliohia (Friday et al. 2015, Barnes et al. 2018, Fortini et al. 2019. These pathogens are believed to be dispersed by wind and four species of invasive ambrosia beetles (Coleoptera: Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, and Xyleborus perforans) (Roy et al. 2020, Roy et al. 2023). On the Island of Hawai'i, hundreds of thousands of ' ohi'a trees have already died from this fungus (https://cms. ...
Metrosideros polymorpha (‘ohi‘a, ‘ohi‘a lehua) is an important foundation species in Hawaiian forest habitats. The genus originated in New Zealand and was dispersed to the Hawaiian archipelago approximately 3.9 million years ago. It evolved into five distinct endemic species and one of these, Metrosideros polymorpha, further differentiated into eight varieties across what are now the main Hawaiian Islands. ‘Ohi‘a is a tree that has great significance in indigenous Hawaiian culture. It is considered a physical manifestation of several principal Hawaiian deities, and serves a broad range of uses in Hawaiian material culture. It occupies a wide diversity of habitats, extending from sea level to over 2,200 m elevation, occupying habitats that range from extremely wet to dry rainfall zones. It is the dominant or co-dominant tree species in wet and mesic forests and is also one of the first woody species to become established on young lava flows. Although ‘ohi‘a is a dominant forest tree it also exhibits many characteristics of a pioneer species.‘Ohi‘a provides the matrix for a wide diversity of endemic plants and animals found in these habitats and functions as the primary vegetation cover on native Hawaiian watersheds, facilitating groundwater recharge and regulating surface runoff. ‘Ohi‘a has shown remarkable resilience by recolonizing forests that were opened up by disturbance, such as the widespread ‘ohi‘a canopy dieback that occurred on East Maui in the 1900s and on the east side of the Island of Hawai‘i in the 1970s. Several human-related conditions threaten the continued stability of Hawaii’s native ecosystems, including invasive plants, plant diseases, introduced animals, and changing climate. The research and conservation legacy of Dr. Dieter Mueller-Dombois helped to expand our knowledge of the ecology and importance of ‘ohi‘a forests, and to increase awareness and appreciation of the remarkable Hawaiian ecosystems that are unique to the world.
... This disease complex is caused by Ceratocystis lukuohia and Ceratocystis huliohia and kills the ecologically and culturally important tree, ʻ ohiʻa (Cannon et al., 2022;Keith et al., 2015). These ambrosia beetles can directly vector the pathogens and also spread them through contaminated frass (boring dust, macerated wood, beetle faeces, and dead beetle parts) (Hughes et al., 2022;Roy et al., 2020;Roy et al., 2023). Xyleborus affinis, X. ferrugineus, and X. perforans are also associated with Macadamia quick decline in agricultural fields in Hawaiʻi, although their role in that disease is unclear (Chang, 1993). ...
Early detection of invasive species is critical for preventing ecological and economic damage and maintaining ecosystem health. In Hawaiʻi, a complex of generalist ambrosia beetle species in the tribe Xyleborini (Coleoptera: Scolytinae) are threatening the health and productivity of forests and crops due to their association with tree diseases such as rapid ʻōhiʻa death (ROD) and key agricultural commodities including coffee and macadamia.
We conducted trapping experiments to determine the efficacy of semiochemicals to attract and repel Xyleborini ambrosia beetles within two ʻōhiʻa ( Metrosideros polymorpha ) forests on the Island of Hawaiʻi. We compared the attraction of beetles to 100% ethanol and a 1:1 mixture of ethanol: methanol at Waiākea Forest Reserve and ʻŌlaʻa Forest in Hawaiʻi Volcanoes National Park. In addition, we tested the extent to which verbenone and verbenone + methyl salicylate repellents (SPLAT® Verb and SPLAT® Beetle Guard, respectively) deterred beetles from baited traps at Waiākea Forest Reserve in two separate experiments.
For all invasive ambrosia beetle species, including Xyleborinus saxesenii , Xyleborus affinis , Xyleborus ferrugineus , Xyleborus perforans, Xylosandrus compactus , and Xylosandrus crassiusculus , more beetles were captured in traps baited with 100% ethanol than 1:1 ethanol: methanol. Across all species, both repellents were effective, with fewer beetles captured in traps equipped with repellents.
Our research demonstrates the utility of semiochemicals for attracting and repelling invasive ambrosia beetle species in Hawaiʻi, and the potential use of these tools for early detection and management strategies.
... C. lukuohia is a wilt pathogen that affects the vascular system of its hosts, resulting in canopy wilt, rapid browning and eventual death [39]. Ecological consequences of C. lukuohia-caused mortality include declines in endemic avifauna and plants [48,49], and research in this field is rapidly developing to understand and combat this new threat [50][51][52]. ...
... The need for immediate action is hampered by the long timelines defining resistance programs, but remote sensing applications have the potential to accelerate disease resistance screening methods. Current research efforts are focused on monitoring disease spread and developing management strategies to combat Ceratocystis-induced M. polymorpha mortality [52,60,61] as well as resistance screening [47,51]. In 2018, the USDA Forest Service (USFS) in partnership with the USDA Agricultural Research Service and Akaka Foundation for Tropical Forests established the 'Ō hi'a Disease Resistance Program ('Ō DRP; www.akakaforests.org/projects/ohia-diseaseresistance-program) in order to identify, propagate, and outplant individuals resistant to C. lukuohia with the goal of restoring regions affected by this pathogen [47,51]. ...
Plant pathogens are increasingly compromising forest health, with impacts to the ecological, economic, and cultural goods and services these global forests provide. One response to these threats is the identification of disease resistance in host trees, which with conventional methods can take years or even decades to achieve. Remote sensing methods have accelerated host resistance identification in agricultural crops and for a select few forest tree species, but applications are rare. Ceratocystis wilt of 'ōhi'a, caused by the fungal pathogen Ceratocystis lukuohia has been killing large numbers of the native Hawaiian tree, Metrosideros polymorpha or 'Ōhi'a, Hawaii's most common native tree and a biocultural keystone species. Here, we assessed whether resistance to C. lukuohia is detectable in leaf-level reflectance spectra (400-2500 nm) and used chemometric conversion equations to understand changes in leaf chemical traits of the plants as indicators of wilt symptom progression. We collected leaf reflectance data prior to artificially inoculating 2-3-year-old M. polymorpha clones with C. lukuohia. Plants were rated 3x a week for foliar wilt symptom development and leaf spectra data collected at 2 to 4-day intervals for 120 days following inoculation. We applied principal component analysis (PCA) to the pre-inoculation spectra, with plants grouped according to site of origin and subtaxon, and two-way analysis of variance to assess whether each principal component separated individuals based on their disease severity ratings. We identified seven leaf traits that changed in susceptible plants following inoculation (tannins, chlorophyll a+b, NSC, total C, leaf water, phenols, and cellulose) and leaf chemistries that differed between resistant and early-stage susceptible plants, most notably chlorophyll a+b and cellulose. Further, disease resistance was found to be detectable in the reflectance data, indicating that remote sensing work could expedite Ceratocystis wilt of 'ōhi'a resistance screenings.
... As a novel disease, the epidemiology of ROD is not fully understood. However, like other Ceratocystis fungal tree diseases, both C. lukuohia and C. huliohia can be transported in ambrosia beetle (Coleoptera: Curculionidae: Scolytinae) frass (i.e., wood particles, faeces, and beetle parts) (Atkinson et al., 2019;Barnes et al., 2018;Roy et al., 2019Roy et al., , 2020 and enter trees via open wounds created by mechanical means (i.e., feral ungulates, humans, extreme weather events) (Cannon et al., 2022). Frass particles contain long-lived resting chlamydospores and can spread in the wind (Atkinson et al., 2019;Roy et al., 2021), soil (via humans and ungulates; Yelenik et al., 2020), and potentially water (Harrington, 2013). ...
... Bolt-reared beetles were aseptically gathered from Boring Dust Traps (BDT; Roy et al., 2019) affixed to gallery entry holes on ROD Ceratocystis-DNA confirmed bolts. Bolts were stored in rearing chambers in the lab at ~25°C as described in Roy et al. (2020). Springstar®, Woodinville, Washington) were placed in each trap collection cup to ensure that beetles were not cross-contaminated, and beetles were collected the following day. ...
... The four requirements listed by Leach (1940) for implicating an insect as a vector of a plant disease are fulfilled when results of the previous study by Roy et al. (2020) (Roeper et al., 1980). Xyleborinus saxesenii, X. affinis, and X. ferrugineus have all been documented to attack healthy trees in various environments (Aguilar-Perez et al., 2007;Granda Giro, 2003;Kovach & Gorsuch, 1985;Merkl & Tusnadi, 1992;Oliver & Mannion, 2001;Rabaglia et al., 2006); less is known of the island pinhole borer, X. perforans. ...
The ecologically and culturally vital tree species, ʻōhiʻa lehua (Metrosideros polymorpha), is threatened by the fungal pathogens Ceratocystis lukuohia and Ceratocystis huliohia, the causal agents of the disease complex called Rapid ʻŌhiʻa Death (ROD). Four inva-sive ambrosia beetle (Coleoptera: Curculionidae: Scolytinae) species in the Xyleborini tribe colonize ROD Ceratocystis-infested 'ōhiʻa and produce inoculum through their frass; however, the potential for direct transmission of the ROD fungi by these beetles was unknown. We fulfilled Leach's rules to support insect transmission of ROD by documenting the visitation of these ambrosia beetles to healthy 'ōhiʻa trees, cultur-ing C. lukuohia and C. huliohia from the ROD-associated beetles using three different collection methods at multiple study sites, and challenging healthy ʻōhiʻa seedlings with beetles that were exposed to both C. lukuohia and C. huliohia cultures. We documented all four invasive ROD-associated ambrosia beetle species including Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, and Xyleborus perforans to regularly visit healthy ʻōhiʻa trees on sticky traps. Viable Ceratocystis propagules were isolated from all species, and C. lukuohia was most commonly isolated of the two ROD-causing fungi. Consistently across all collection techniques, ROD Ceratocystis spp. were detected on just under 3% of all assayed beetles, with the highest detection rate from X. affinis. All four beetle species were capable of directly transmitting both pathogens to healthy ʻōhiʻa seedlings with a high rate of transfer. Ceratocystis spp. are highly virulent pathogens in trees, and a single inoculation can result in tree death, therefore any direct transmission is a cause for concern. After meeting the criteria of Leach's rules, we propose that Xi. saxesenii, X. affinis, X. ferrugineus, and X. perforans are vectors of C. lukuohia and C. huliohia, particularly in areas of high ROD pressure and tree stress. K E Y W O R D S ambrosia beetle, Ceratocystis, Hawaii, Metrosideros, Rapid Ohia Death, vector transmission, Xyleborini This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
... While windblown dispersal of infective urediniospores is the primary mechanism for natural transmission of A. psidii (Carnegie and Cooper 2011;McTaggart et al. 2018), there are significant unanswered questions about natural pathways for dispersal and transmission of both C. lukuohia and C. huliohia. The movement of Ceratocystis-contaminated ambrosia beetle (Coleoptera: Curculionidae) frass is the leading hypothesis for the spread of ROD (Roy et al. , 2020a(Roy et al. , 2021, although long distance wind dispersal is not well understood. Early patterns of ROD spread suggested that airborne movement of potentially infective propagules in frass was responsible for spread of the disease on prevailing trade winds from the Puna District of Hawaiʻi Island to the South Kona District of the island (Harrington et al. 2021). ...
The invasive rust Austropuccina psidii was detected in the Hawaiian Islands in 2005 and has become widely established throughout the archipelago in both native and introduced species of Myrtaceae. Initial predictions about the impacts of the fungus on native ʽōhiʽa lehua ( Metrosideros polymorpha ), a keystone native tree, have not materialized, but there is ongoing concern that introductions of new genotypes of the fungus could lead to widespread mortality with catastrophic effects on native ecosystems. By contrast, two recently emergent Ascomycete pathogens, Ceratocystis lukuohia ( Ceratocystis wilt of ‘ōhi‘a) and C. huliohia ( Ceratocystis canker of ‘ōhi‘a), collectively known to cause Rapid ʽŌhiʽa Death (ROD), are causing significant mortality in native forests on Hawaiʻi and Kauaʻi Islands, but pathways of spread are still incompletely understood. We used a network of passive environmental samplers for collecting windblown urediniospores of Austropuccina to evaluate the effectiveness of environmental monitoring to detect seasonal and landscape-scale differences in airborne propagules of this rust on Hawai`i Island. The samplers were also used to determine if windborn ambrosia beetle frass or spores of Ceratocystis can spread long distances. We found frequent detections and regional and seasonal differences in numbers of samplers that were positive for urediniospores of Austropuccinia , but little evidence of long-distance airborne dispersal of the ROD-causing fungi. The simple, inexpensive platform for sampling airborne fungal spores that we used may have value as a monitoring tool for detecting spread of airborne fungal pathogens, evaluating habitats for suitability for restoration efforts, and for detecting new pathogen introductions, particularly new Austropuccinia genotypes both in Hawaiʻi and other parts of the world.
... After completing each transect, all equipment was thoroughly shaken out and visually inspected to ensure that no arthropods remained inside. On Hawaii, due to the threat of Rapid Ohia Death (Fortini et al., 2019;Roy et al., 2020), equipment was disinfected with 70% isopropanol between sites. ...
Islands make up a large proportion of Earth’s biodiversity, yet are also some of the most sensitive systems to environmental perturbation. Biogeographic theory predicts that geologic age, area, and isolation typically drive islands’ diversity patterns, and thus potentially impact non‐native spread and community homogenization across island systems. One limitation in testing such predictions has been the difficulty of performing comprehensive inventories of island biotas and distinguishing native from introduced taxa. Here, we use DNA metabarcoding and statistical modeling as a high throughput method to survey community‐wide arthropod richness, the proportion of native and non‐native species, and the incursion of non‐natives into primary habitats on three archipelagos in the Pacific ‐ the Ryukyus, the Marianas and Hawaii ‐ which vary in age, isolation and area. Diversity patterns largely match expectations based on island biogeography theory, with the oldest and most geographically connected archipelago, the Ryukyus, showing the highest taxonomic richness and lowest proportion of introduced species. Moreover, we find evidence that forest habitats are more resilient to incursions of non‐natives in the Ryukyus than in the less taxonomically rich archipelagos. Surprisingly, we do not find evidence for biotic homogenization across these three archipelagos: the assemblage of non‐native species on each island is highly distinct. Our study demonstrates the potential of DNA metabarcoding to facilitate rapid estimation of biogeographic patterns, the spread of non‐native species, and the resilience of ecosystems.
... trees on Hawaiʻi island, and recently found also on Kauaʻi, Maui, and Oʻahu (Keith et al. 2015). Roy et al. (2018) and Roy et al. (2020) found Xyleborus ferrugineus, X. affinis, X. perforans, X. simillimus Perkins, and Xyleborinus saxesenii (Ratzeburg) to inhabit ʻōhiʻa trees and to excavate frass containing viable fungal spores, and though the mechanisms of spread of this disease in forests are not yet fully determined, bark beetles and their frass are suggested as a likely important factor. Phymastichus holoholo uses at least three of these Xyleborus beetles that infest ʻōhiʻa lehua as hosts, and along with P. xylebori may have the potential to be used as a biological control agent for augmentative release in forests where this disease is spreading or may spread in the future. ...
A third species in the genus Phymastichus LaSalle (Hymenoptera: Eulophidae), Phymastichus holoholo sp. nov., is described from specimens endoparasitic on adult Xyleborus beetles in Hawaiʻi. Plant and insect host records known for this species, and aspects of its searching, oviposition, and emergence behavior are discussed and illustrated with photographs and video. This new species, along with Phymastichus xylebori which is also present in Hawaiʻi, has potential as a biological control agent against Xyleborus beetles where they are problematic. Of special interest is their potential as natural enemies of X. ferrugineus, X. affinis, and X. perforans, which have recently been implicated in possibly spreading Rapid ʻŌhiʻa Death in Hawaiʻi. Some aspects of their potential use to combat this disease, as well as some important but as of yet unanswered questions, are discussed. Two observed instances of parasitism by the newly described species of beetles in the Euwallacea fornicatus species complex, Euwallacea fornicatus (sensu stricto) and Euwallacea perbrevis, are also reported.
... While much effort has been invested into the epidemiology of these two pathogens, potential dispersal agents, vectors, and the roles they play in pathogen dispersal are still being researched. Frass (boring dust) created when ambrosia beetles (Xyleborus ferrugineus (Fabricius), X. affinis Eichhoff, X. perforans (Wollaston), X. simillimus Perkins, and Xyleborinus saxesennii (Ratzburg)) attack and tunnel into diseased trees can harbor viable fungal propagules (Roy et al. 2019(Roy et al. , 2020. One hypothesis is that windblown Ceratocystiscontaminated frass particles are involved in the spread of these pathogens (Barnes et al. 2018), but the role of beetle frass in long-and short-range dispersal of fungal spores is not understood. ...
Metrosideros polymorpha Gaud. (‘ōhi‘a) is the most abundant native forest tree in Hawai‘i and a keystone species of cultural, ecological, and economic importance. ‘Ōhi‘a forests, particularly on Hawaiʻi Island, are being severely impacted by Rapid ‘Ōhi‘a Death (ROD), which is caused by the fungal pathogens Ceratocystis lukuohia and C. huliohia. ROD is characterized by branch dieback, crown wilting, and mortality. Initial disease resistance screening of four varieties of M. polymorpha with C. lukuohia demonstrated that varieties may differ in susceptibility. Several survivors of field or screening-based infections still exist, providing strong impetus for the establishment of the ‘Ōhiʻa Disease Resistance Program (ʻŌDRP). Here, we outline a framework for guiding the ʻŌDRP throughout the process of identifying and developing ROD resistance in M. polymorpha and, possibly, all Hawaiian Metrosideros species. Core ʻŌDRP projects include: (1) evaluating and operationalizing methods for greenhouse-based production and screening of test plants; (2) greenhouse screening of seedlings and rooted cuttings sampled from native Metrosideros throughout Hawaiʻi; (3) establishing field trials to validate results from greenhouse assays; (4) understanding environmental and genetic drivers of resistance to characterize the durability of resistance to ROD; (5) developing remote sensing and molecular methods to rapidly detect ROD-resistant individuals; and (6) conducting breeding trials to improve the degree and durability of ROD resistance. Ultimately, the ʻŌDRP seeks to produce ROD-resistant material for the perpetuation of M. polymorpha across Hawai‘i, with the goal of preserving the ecology, culture, and communities that are dependent on this tree species.
... Ceratocystis propagules were found on the related ambrosia beetle genus, Xyleborus [68]. According to Roy et al. [69], Xyleborus affinis is one of the ambrosia beetle species found to be a suspected spreading vector for Ceratocystis lukuohia on Metrosideros polymorpha host in Hawai'i. Propagules of C. lukuohia were also found on X. simillimus [68,69]. ...
... According to Roy et al. [69], Xyleborus affinis is one of the ambrosia beetle species found to be a suspected spreading vector for Ceratocystis lukuohia on Metrosideros polymorpha host in Hawai'i. Propagules of C. lukuohia were also found on X. simillimus [68,69]. A bark beetle, Hypocryphalus mangiferae, was described as a vector for C. manginecans in Pakistan, Brazil, and Oman [66,70,71]. ...
Ceratocystis wilt disease surveys were conducted in three selected Malaysian Acacia mangium plantations. These completed surveys revealed the occurrence of the wilt disease, with the incidence of infection ranging from 7.5% to 13.6%. Signs of wood-boring insects, bark peeling due to squirrel activity, and pruning wounds were often associated with this disease. The fungus most frequently isolated from the diseased trees was the Ceratocystis fungus. The analysis on the morphological characteristics has identified the fungus as Ceratocystis fimbriata complex. Phylogenetic analysis based on the sequences of the ITS, and concatenated sequences of EF1α-βT regions grouped the isolates within the C. fimbriata sensu stricto, in comparison to other C. fimbriata isolates. Pathogenicity tests were conducted on six to nine-month-old healthy A. mangium seedlings by inoculating these seedlings with eight out of the 16 isolates. The results demonstrated that all the isolates were pathogenic, with mortality beginning as early as two weeks after inoculation. However, an ANOVA test indicated a significant difference between the pathogenicity levels among the fungal isolates. The results also showed that pathogen aggressiveness was not correlated with geographical origin. A host range test was also conducted by using C. fimbriata SSB3 and FRIM1162 isolates against several forest plantation species. The findings suggested that only A. mangium was susceptible to C. fimbriata. The other species remained healthy with no symptoms of infection even after seven weeks of treatment, as compared to the A. mangium species, where between 38 to 60% of the inoculated plants had died. This study provides new information on the status of Ceratocystis wilt disease, especially on the occurrence and effects on A. mangium plantation, by giving insights on how to control and manage this ferocious plant pathogen in the future.
