Ambrosia Beetle Research Articles

First record of non-native Xylosandrus compactus and Anisandrus maiche (Coleoptera: Curculionidae, Scolytinae) in Slovenia.

The introduction of non-native organisms into new areas may pose major threats to natural ecosystems. Therefore, continuous and careful national surveys for the interception of invasive non-native species are necessary. During the national survey of quarantine species in 2023, two new non-native ambrosia beetles, Anisandrus maiche (Kurentzov) and Xylosandrus compactus (Eichhoff), were recorded in Slovenia. Anisandrus maiche was recorded in three locations in the eastern part of Slovenia, with a total of 386 individuals. Three individuals of Xylosandrus compactus were collected in one location near the port of Koper. We discuss the possible pathways of introduction and dispersal.

Effects of biochar on ambrosia beetle attacks on redbud and pecan container trees

Abstract Mitigating tree stress can be a valuable strategy to combat ambrosia beetles, such as the granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky; Coleoptera: Curculionidae, Scolytinae) under nursery conditions. Biochar and kaolin clay are known for their stress-relieving properties but their indirect effects on ambrosia beetle in ornamental or pecan (Carya spp.) trees have not been determined. Although entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) and Trichoderma spp. (Hypocreales: Hypocreaceae) have shown effectiveness against adult ambrosia beetles, their role in reducing tree attacks is unclear. Thus, the objective was to determine the effects of biochar, kaolin clay, permethrin (industry standard), and entomopathogenic fungi on reducing ambrosia beetle attacks on young redbud (Cercis canadensis L.; Fabaceae) and pecan trees. The treatments were biochar, kaolin clay, permethrin, biochar + permethrin, kaolin clay + permethrin, B. bassiana, Trichoderma spp., and a nontreated control. Compared to the nontreated trees, biochar and biochar + permethrin treatments significantly reduced ambrosia beetle attacks on redbud trees. Kaolin clay, permethrin, B. bassiana, and Trichoderma spp. did not significantly reduce the number of ambrosia beetle attack holes when compared with the nontreated trees. This suggests that biochar can reduce ambrosia beetle attacks on ornamental trees and should be further evaluated for longer-term effects for multiple seasons.

Impact of laurel wilt on the avocado germplasm collection at the United States Department of Agriculture, Agricultural Research Service, Subtropical Horticulture Research Station

Abstract In late 2020, laurel wilt impacted the avocado collection at the United States Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository, Subtropical Horticulture Research Station in Miami, Florida. Monitoring of the ambrosia beetle (Coleoptera: Curculionidae) community over the next 18 months suggested that the primary vector, Xyleborus glabratus Eichhoff, was likely not responsible for spreading the fungal pathogen (Harringtonia lauricola [T.C. Harr., Fraerich & Aghayeva] Z.W. de Beer & M. Procter; Ophiostomatales). Rather, eight secondary vectors were detected in greater numbers, with Xyleborinus saxesenii (Ratzeburg) being the most abundant. After detection of laurel wilt, beetle numbers increased for 2–4 months, then gradually declined over the next year. This pest suppression was likely due to several countermeasures, including the prompt removal of infected trees and prophylactic macroinfusions with propiconazole fungicides. In addition, to preserve the genetic diversity of the Miami avocado germplasm, the Subtropical Horticulture Research Station is collaborating with other Agricultural Research Service facilities to establish backup collections at alternative locations free of the laurel wilt pathogen and its beetle vectors.

Damage to Sweet Chestnut Orchards in Croatia due to Invasive Alien Bark Beetle Xylosandrus germanus

Black stem borer, Xylosandrus germanus (Coleoptera: Scolytinae), was first recorded in Croatia in 2009. Until now, the insect has been reported only as a part of ambrosia beetles entomofauna in oak stands (Quercus robur and Quercus petraea). In 2021, severe attack of ambrosia beetles causing tree decline and mortality have been observed in three orchards of hybrid sweet chestnut (Castanea sativa x Castenea crenata). Orchards near Topusko, Marija Bistrica and Vugrovec were inspected for the symptoms. Twenty-seven adult ambrosia beetle specimens were collected from eight samples of damaged sweet chestnut trees, and were identified according to their morphology. All 27 ambrosia beetles were morphologically identified as X. germanus. This is the first record of black stem borer causing damage on cultivated sweet chestnut in Croatia. Considering similar reports from Italy and Slovenia, X. germanus could be regarded as a new, potentially damaging pest in chestnut plantations.

Chemical control of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and Fusarium euwallaceae in American sweetgum (Liquidambar styraciflua)

The polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) is a pest of global significance. PSHB is an ambrosia beetle which, together with its mutualistic fungi (including Fusarium euwallaceae), can cause the death of more than 100 tree species in invaded ranges. Management of PSHB mostly relies on the removal of infested plant material. Chemical control options have been investigated only in the USA and Israel and only on a few tree species. This study evaluated four chemical treatments for the therapeutic control of PSHB on American sweetgum (Liquidambar styraciflua) in South Africa (1) bifenthrin + surfactant (alcohol ethoxylate), (2) cypermethrin + surfactant (vitamin E) + salicylic acid, (3) emamectin benzoate, and (4) propiconazole. Trees were inoculated with F. euwallaceae and mature PSHB females using a novel technique to document fungal lesion development and PSHB colony establishment success. The bifenthrin and cypermethrin treatments reduced additional PSHB colonisation attempts on treated trees by ca. 40%, while the other treatments had no effect. Colony establishment success was reduced in all treatments by between 20 and 40%. Fungal growth was inhibited only after the application of propiconazole by ca. 36%. Gallery length and the number of PSHB individuals in successful colonies were unaffected by any of the chemical treatments. These results indicate that chemical control of PSHB is only partially effective. Successful PSHB management will likely depend on a combination of chemical control options and other control strategies in an integrated pest management program.

Identification of the ambrosia beetle Xyleborinus saxesenii (Ratzeburg, 1837) (Coleoptera: Curculionidae: Scolytinae) from frass and adult DNA by TaqMan Probe real‐time‐PCR

AbstractA molecular tool has been set up for the unambiguous molecular identification of the ambrosia beetle, Xyleborinus saxesenii (Ratzeburg, 1837) (Coleoptera Curculionidae Scolytinae), the cosmopolitan fruit‐tree pinhole borer, widely distributed in temperate regions of the five continents, where it infests a wide range of hardwoods and softwoods. The test was based on real‐time PCR with TaqMan probe technology and was developed on whole insect bodies (adults) as well as on frass produced by the beetle. The test was shown to meet the criteria established by EPPO for the harmonization of molecular diagnostic methods. In particular, the test gave good results in terms of analytical specificity (inclusivity and exclusivity) and analytical sensitivity, and was fully repeatable and reproducible. Since X. saxesenii is one of the most commonly intercepted ambrosia beetles during phytosanitary controls worldwide, this practical diagnostic tool will be useful for its rapid identification of the beetle in biological material (frass, body fragments). The test can be useful in countries where X. saxesenii is a quarantine species, as well as in the EPPO region.

In-gallery social behaviors of the ambrosia beetle, Xylosandrus germanus (Coleoptera: Curculionidae).

The east Asian ambrosia beetle Xylosandrus germanus (Blanford) was first detected in the United States in 1932. It now occurs across much of eastern North America and parts of the Pacific Northwest. It attacks a broad range of stressed, woody hosts including ornamental and orchard species. The foundress tunnels into the sapwood of hosts where it cultures a symbiotic fungus as food for its offspring. A few other ambrosia beetles have been shown to possess a facultatively eusocial structure among gallery members, but this has not been described for Xylosandrus spp. Using a novel artificial diet arena, we quantified the behaviors of X. germanus larvae and adults (foundress and mature offspring) over 10 wk inside their galleries. Foundresses were responsible for constructing the gallery. They also initially tended the fungal garden and brood but eventually spent most of their time blocking the gallery entrance. Larvae were mainly observed to feed, crawl, or be inactive within the gallery, regardless of the absence or presence of adult siblings. Adult female offspring were primarily inactive, likely due to dormancy. Adult male offspring actively crawled and attempted to mate with their sisters before eventually dispersing out of the gallery. Cooperative hygienic behaviors (removal of frass, cannibalism of dead nest mates, grooming siblings) were observed but a division of labor among offspring was not clear. Rather, foundress behaviors were mostly distinct from offspring behaviors, particularly as the gallery aged. Because no overlap in generations occurred, X. germanus displays a quasisocial structure.

Cladosporium-Insect Relationships.

The range of interactions between Cladosporium, a ubiquitous fungal genus, and insects, a class including about 60% of the animal species, is extremely diverse. The broad case history of antagonism and mutualism connecting Cladosporium and insects is reviewed in this paper based on the examination of the available literature. Certain strains establish direct interactions with pests or beneficial insects or indirectly influence them through their endophytic development in plants. Entomopathogenicity is often connected to the production of toxic secondary metabolites, although there is a case where these compounds have been reported to favor pollinator attraction, suggesting an important role in angiosperm reproduction. Other relationships include mycophagy, which, on the other hand, may reflect an ecological advantage for these extremely adaptable fungi using insects as carriers for spreading in the environment. Several Cladosporium species colonize insect structures, such as galleries of ambrosia beetles, leaf rolls of attelabid weevils and galls formed by cecidomyid midges, playing a still uncertain symbiotic role. Finally, the occurrence of Cladosporium in the gut of several insect species has intriguing implications for pest management, also considering that some strains have proven to be able to degrade insecticides. These interactions especially deserve further investigation to understand the impact of these fungi on pest control measures and strategies to preserve beneficial insects.

Volatiles from nutritional fungal symbiont influence the attraction of Anisandrus maiche (Coleoptera: Curculionidae) to ethanol-baited traps.

Anisandrus maiche Stark (Coleoptera: Curculionidae: Scolytinae) is a non-native ambrosia beetle from central Asia that has been spreading throughout the eastern United States since 2005. Preferred hosts of A. maiche are not well characterized within its currently invaded range, but it is established in managed and natural forests throughout Indiana. Current monitoring and detection efforts for this beetle rely on ethanol-baited traps, but fungal volatiles may alter the attraction of A. maiche to ethanol. In this study, we conducted trapping experiments in Indiana to determine the extent to which a suite of common fungal alcohols influences the response of A. maiche to ethanol-baited traps. We then evaluated isoamyl and isobutyl alcohol as potential attractants for A. maiche and their ability to enhance attraction to ethanol. Lastly, we used SPME-GC-MS to identify volatiles from Ambrosiella cleistominuta (Mayers & Harr.), the fungal symbiont of A. maiche, grown for 7 and 14 days on malt extract agar. Benzyl alcohol, isobutyl alcohol, hexanol, methyl phenylacetate, phenethyl alcohol, and piperitone reduced the attraction of A. maiche to ethanol-baited traps in the field. Moreover, adding methyl benzoate and isoamyl alcohol individually to ethanol-baited traps did not further increase A. maiche capture. When paired with ethanol, isoamyl alcohol repelled beetles in the early flight period but did not significantly increase trap capture during the fall flight. These results represent a first step in understanding the role of fungal volatiles in the colonization behavior of A. maiche and may ultimately inform management strategies for this species.

Anisandrusbolavenensis sp. nov. (Col.: Curculionidae, Scolytinae, Xyleborini), a new ambrosia beetle from Laos.

The ambrosia beetle genus Anisandrus Ferrari, 1867, is a member of the bark and ambrosia beetle subfamily Scolytinae, Tribe Xyleborini. Currently, it is comprised of 40 species of which four species were recorded in Laos. A new species, Anisandrusbolavenensis sp. nov. is described from the Bolaven Plateau in southern Laos. With the inclusion of the species described and recorded here, the diversity of Anisandrus is increased to 41 species, of which five occur in Laos. New distribution records, a synoptic list and a key to the Anisandrus of Laos PDR are presented.

Insights into the complexities of fungus‐insect‐plant interaction: The laurel wilt disease

AbstractLaurel wilt disease, caused by the fungus Harringtonia lauricola and transmitted by the ambrosia beetle Xyleborus glabratus, poses a significant ecological and economic threat to various species of the Lauraceae family, particularly avocado. The disease is characterized by the formation of tyloses blocking xylem vessels, hindering water conductance, and decreasing leaf gas exchange. The relationship between the fungus and the beetle is complex and not fully understood, which can be described, in general, as ambrosial symbiosis depending on the habitat. The secretome of the pathogen includes hydrolytic enzymes that aid in colonization and resistance of host defence. This paper reviews the current understanding of the causes, impacts, and management strategies for laurel wilt disease. Also, it provides an overview of the complex relationship between the fungal pathogen and its beetle vector and explores the various virulence factors and secretome of H. lauricola that contribute to the aggressive nature of the disease. Moreover, this review states the ecological and economic impacts of laurel wilt, particularly on ecologically and economically valuable plants such as avocado. Current management strategies for controlling the disease, including the use of insecticides, fungicides, and biological control methods, are reviewed. Finally, we highlight some critical key points in ambrosia symbiosis biology that are of importance for disease control.

Composition and Diversity of the Endobacteria and Ectobacteria of the Invasive Bark Beetle Hylurgus ligniperda (Fabricius) (Curculionidae: Scolytinae) in Newly Colonized Areas.

Hylurgus ligniperda (Fabricius) (Curculionidae: Scolytinae) is a new invasive pest beetle in China, which colonized the Shandong province, causing devastating damage. Originating in Europe, it has spread to Oceania, Asia, North and South America. Bacterial associates have been frequently reported to play a vital role in strengthening the ecological adaptations of bark and ambrosia beetles. The environmental adaptability of H. ligniperda may be supported by their associated bacteria. Bacterial communities colonizing different body parts of insects may have different functions. However, little is known about the bacteria associated with H. ligniperda and their potential involvement in facilitating the adaptation and invasion of the beetles into new environments. In this study, we employed high-throughput sequencing technology to analyze the bacterial communities associated with male and female adults of H. ligniperda by comparing those colonizing the elytra, prothorax, and gut. Results showed that the bacterial communities of male and female adults were similar, and the elytra samples had the highest bacterial diversity and richness, followed by the gut, while the prothorax had the lowest. The dominant phyla were Proteobacteria, Firmicutes, and Actinobacteriota, while the dominant genera were Serratia, Lactococcus, Rhodococcus, unclassified Enterobacteriaceae, and Gordonia. Among these, Rhodococcus and Gordonia were the specific genera of endobacteria and ectobacteria, respectively. Differences in the distribution of associated bacteria may suggest that they have different ecological functions for H. ligniperda. The results of functional prediction showed that bacteria were enriched in terpenoid backbone biosynthesis, degradation of aromatic compounds, limonene and pinene degradation, neomycin, kanamycin and gentamicin biosynthesis, indicating that they may assist their beetles in synthesizing pheromones, degrading toxic secondary metabolites of host trees, and antagonizing pathogenic fungi. These results help us understand the interaction between H. ligniperda and bacteria and highlight possible contributions to the invasion process.

Fusarium kuroshium is the primary fungal symbiont of an ambrosia beetle, Euwallacea fornicatus, and can kill mango tree in Japan

This study identifies fungi associated with Euwallacea fornicatus and determines whether these fungal species play the role of primary symbiont. E. fornicatus adults that emerged from the branches of infested trees in Okinawa main island, Japan, were collected and used to isolate fungi. Fusarium kuroshium and Penicillium citrinum were the most dominant fungal associates of females and males, respectively. F. kuroshium was much more frequently isolated from the head, including mycangia (fungus-carrying organs), of females than any other body parts. We inoculated healthy mango saplings with F. kuroshium or F. decemcellulare, both of which were symbionts of E. fornicatus females infesting mango trees. F. kuroshium decreased leaf stomatal conductance and rate of xylem sap-conduction area and increased length and area of xylem discoloration of the saplings, thereby weakening and killing some. These results suggest that F. kuroshium, a mycangial fungus of E. fornicatus, inhibits water flow in mango trees. This study is the first to report that F. kuroshium causes wilt disease in mango trees and that it is a primary fungal symbiont of E. fornicatus.

Characterization of Terpenoids from the Ambrosia Beetle Symbiont and Laurel Wilt Pathogen Harringtonia lauricola.

Little is known concerning terpenoids produced by members of the fungal order Ophiostomales, with the member Harringtonia lauricola having the unique lifestyle of being a beetle symbiont but potentially devastating tree pathogen. Nine known terpenoids, including six labdane diterpenoids (1-6) and three hopane triterpenes (7-9), were isolated from H. lauricola ethyl acetate (EtOAc) extracts for the first time. All compounds were tested for various in vitro bioactivities. Six compounds, 2, 4, 5, 6, 7, and 9, are described functionally. Compounds 2, 4, 5, and 9 expressed potent antiproliferative activity against the MCF-7, HepG2 and A549 cancer cell lines, with half-maximal inhibitory concentrations (IC50s) ~12.54-26.06 μM. Antimicrobial activity bioassays revealed that compounds 4, 5, and 9 exhibited substantial effects against Gram-negative bacteria (Escherichia coli and Ralstonia solanacearum) with minimum inhibitory concentration (MIC) values between 3.13 and 12.50 μg/mL. Little activity was seen towards Gram-positive bacteria for any of the compounds, whereas compounds 2, 4, 7, and 9 expressed antifungal activities (Fusarium oxysporum) with MIC values ranging from 6.25 to 25.00 μg/mL. Compounds 4, 5, and 9 also displayed free radical scavenging abilities towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide (O2-), with IC50 values of compounds 2, 4, and 6 ~3.45-14.04 μg/mL and 22.87-53.31 μg/mL towards DPPH and O2-, respectively. These data provide an insight into the biopharmaceutical potential of terpenoids from this group of fungal insect symbionts and plant pathogens.

Changes in forest structure over 23 years under disturbances in a warm temperate rain forest on Yakushima Island, Japan

AbstractClarifying the influence of disturbances by biotic and abiotic agents on long‐term changes in forest structure and demographic rates is an important task of forest ecology. Here, we investigated changes in forest structure and demographic rates and the effects of biotic and abiotic factors (sika deer, ambrosia beetle, neighborhood trees, and indices of strong wind and wetness) in a 4‐ha long‐term ecological study plot in a lowland warm temperate rain forest on Yakushima Island, Japan, from 1996 to 2019 for three regeneration groups related to gap dynamics (gap demander: GD, light shade tolerant: LS, and strong shade tolerant: SS). GD had relatively lower recruitment and survival than LS and/or SS. Changes in demographic rates were not significantly correlated with those in the index of strong wind in any regeneration group. The effects of sika deer on demographic rates did not differ among groups. Stems of Fagaceae species belonging to LS attacked by ambrosia beetles recorded in 2013 did not significantly differ in RGR and survival rates. Our results indicate that despite the relatively long monitoring period of 23 years, we did not detect significant effects of strong winds on demographic rates among regeneration groups, and shade‐tolerant species (LS and SS) showed better demographic performance than light‐demanding species (GD) and an increase in total basal area over time. We need longer monitoring of forest dynamics to understand forest responses to disturbances considering several factors, including the time lag of demographic responses to disturbances and the long‐term effects of disturbances.

Trunk injection to control Xylosandrus germanus (Coleoptera: Curculionidae) in topworked apple trees.

Xylosandrus germanus (Blandford) is an invasive species of ambrosia beetle known to attack apple trees in North America. Xylosandrus germanus are attracted to ethanol produced by stressed and injured trees and can be a serious problem when grafting a new cultivar onto established fruit trees (topworking). The objective of this study was to evaluate the efficacy of 2 insecticides (emamectin benzoate and azadirachtin) and injection timing (fall and spring) on their ability to control X. germanus colonization in apple trees with simulated topworking. Our study shows evidence that both emamectin benzoate and azadirachtin injections can reduce X. germanus infestations; however, our results were inconsistent. The timing of injections influenced X. germanus, with spring injected azadirachtin being more effective than fall injections. Residue analyses of emamectin benzoate and azadirachtin showed the presence of residues in woody tissue comparable to those found in leaves.

Isolasi Jamur yang Berasosiasi dengan Kumbang Ambrosia pada Pohon Angsana (Pterocarpus indicus)

Insect pests are organisms that can damage plants and have a high level of damage. However, it is not only insects that need to be watched out for but also the microorganisms they carry inside and outside their bodies. These insects are referred to as vectors. Ambrosia beetle is a plant vector that carries both saprophytic and pathogenic fungi. There is little information about ambrosia beetles and the mushrooms they carry, so they need to be studied further. This study aimed to determine the fungi associated with the ambrosia beetle on Angsana trees (Pterocarpus indicus). The research used purposive sampling by examining the symptoms and signs of an ambrosia beetle attack. The identification process is based on morphological forms and entomology manuals. The results obtained based on morphological identification showed that the ambrosia beetle came from the genus Cryphalus sp. In contrast, the associated fungus comes from the genus Geosmithia sp. It is known that the fungus Geosmithia sp. can act as a pathogen so that it can damage Angsana trees.

Major Pathogens Affecting Carob in the Mediterranean Basin: Current Knowledge and Outlook in Italy.

The main pathogens affecting the carob (Ceratonia siliqua) tree in the Mediterranean basin are described in this overview. The most widespread diseases periodically occurring in carob orchards are powdery mildew (Pseudoidium ceratoniae) and cercospora leaf spot (Pseudocercospora ceratoniae). The causal agents of "black leaf spots" (e.g., Pestalotiopsis, Phyllosticta and Septoria spp.) are responsible for symptoms similar to those previously mentioned for foliar diseases, but are reported in carob orchards at a negligible frequency. Likewise, canker and branch diebacks caused by fungal species belonging to Botryosphaeriaceae are almost never recorded. Among the rots of wood tissues that may compromise old carob specimens, "brown cubical rot" caused by Laetiporus sulphureus is the most widespread and recurrent issue; this pathogen is also well-known for producing edible fruit bodies that are appreciated for pharmaceutical and industrial purposes. On the other hand, "white rots" caused by Fomes and Ganoderma species are less common and reported for the first time in this review. Gall-like protuberances on twigs of uncertain aetiology or tumors on branches associated with Rhizobium radiobacter are described, although these symptoms are seldom detected, as they are also observed for necrotic leaf spots caused by Pseudomonas syringae pv. ciccaronei. A worldwide list of pathogens not yet recorded but at high risk of potential introduction in Italian carob-producing areas is also provided. Finally, concerns related to new phytopathogenic fungi vectored by the invasive Xylosandrus compactus ambrosia beetle are addressed. All the described pathogens could become limiting factors for carob production in the near future, because they could be favored by high-density orchards, the increasing global network of trade exchanges, and the high frequency at which extreme events related to climate change occur globally. Thus, symptoms and signs, causal agents, epidemiology, and, whenever applicable, recommendations for disease prevention and management are provided in this review.

Erwiniaceae bacteria play defensive and nutritional roles in two widespread ambrosia beetles.

Ambrosia beetles are fungal-growing insects excavating galleries deep inside the wood. Their success as invaders increased scientific interest towards them. However, most studies on their microbiota targeted their fungal associates whereas the role of bacterial associates is understudied. To explore the role of abundant microbial associates, we isolated bacteria from active galleries of two widespread ambrosia beetles, Xylosandrus crassiusculus and X. germanus. These isolates were classified within the Erwiniaceae family and through a phylogenetic analysis including isolates from other insects we showed that they clustered with isolates obtained from ambrosia and bark beetles, including Erwinia typographi. The whole genome analysis of the isolate from active galleries of X. crassiusculus suggested that this bacterium plays both a nutritional role, by providing essential amino acids and enzymes for the hydrolysis of plant biomass, and a defensive role, by producing antibiotics. This defensive role was also tested in vitro against fungi, including mutualists, common associates, and parasites. The bacteria inhibited the growth of some of the common associates and parasites but did not affect mutualists. Our study supported the hypothesis of a mutualist role of Erwiniaceae bacteria in ambrosia beetles and highlighed the importance of bacteria in maintaining the symbiosis of their host with nutritional fungi.

Fungi associated with the ambrosia beetle Xyleborus perforans (Coleoptera: Curculionidae: Scolytinae) on drought-stressed Pinus in New South Wales, Australia

Ambrosia beetles have co-evolved symbiotic relationships with an array of fungal partners. Mutualistic fungal partners are often highly successful in vertical transmission between beetle generations. These persisting relationships can alter beetle behaviour, resulting in the opportunity to occupy new ecological niches and to spread geographically. In Australia, ambrosia beetles are not currently considered a significant pest in commercial Pinus plantations, where the bark beetle Ips grandicollis is known as the primary invader of stressed trees. However, in 2019, ambrosia beetles Xyleborus perforans and X. bispinatus, co-occurring with I. grandicollis, were found to have colonised a large proportion of drought-stressed trees in commercial Pinus plantations in north-east New South Wales. In this study, X. perforans (the most prevalent of two Xyleborus spp.) was collected from infested dead and dying trees in two NSW Pinus plantations. Fungal isolates of suspected Pinus pathogens were recovered from beetle mycangia and exoskeletons as well as ambrosia beetle galleries. Morphological examination and multilocus sequence analysis identified five fungi associated with X. perforans: Fusarium parceramosum, Fusarium aff. solani, Ophiostoma ips, Raffaelea deltoideospora and Sporothrix pseudoabietina. For Australia, this is the first report of F. parceramosum, as well as the first records of O. ips, R. deltoideospora and S. pseudoabietina being vectored by Xyleborus. Pathogenicity tests were performed on seedlings of three Pinus spp., with O. ips producing significantly longer lesions than the other fungi. This study demonstrates the potential for seemingly harmless ambrosia beetles to vector plant pathogens in Australian forests, providing a mode of disease transmission that should be considered in plantation management and forest biosecurity.