Cypress canker, caused by several species of Seiridium, affects Cupressaceae worldwide. Of the seven described pathogens that cause this disease, S. cardinale is one of the most aggressive and widespread. This study examined the genetic diversity of S. cardinale isolates from the Southern Hemisphere, with a focus on South Africa and New Zealand. Three S. cardinale genomes were sequenced to evaluate the utility of existing microsatellite markers and to identify and develop new microsatellite markers. Sixty isolates from the Southern Hemisphere, together with 22 reference strains from Europe and California, were genotyped at 10 loci. Genetic diversity was high for the South African (H exp = 0.80) and New Zealand (H exp = 0.67) populations, though rarefaction indicated even greater diversity in California, the presumed native range of the pathogen. Southern Hemisphere populations showed no evidence of recombination and isolates were closely related to one another and to Californian strains, whereas European strains formed a distinct lineage. Three genetic lineages were detected among the New Zealand isolates, all closely related to South African strains. Collectively, these results suggest multiple introductions of S. cardinale into Southern Hemisphere countries from California, likely facilitated by trade in Cupressaceae trees, as well as subsequent accidental movement of the pathogen between South Africa and New Zealand.

Arthropods are crucial to ecosystems, yet face multiple threats, with recent studies indicating global declines and many species at risk of extinction. The primary threats include land use change, climate change, invasive species, pesticides, pollution, and overexploitation, all of which can interact to compound this vulnerability. Although most insect conservation research comes from the Global North, South Africa has a long history of insect (and other arthropod) conservation, including comprehensive IUCN Red List assessments. We systematically assessed South African insect conservation in the peer reviewed literature (2000–2024) to identify research patterns, gaps, and implementation priorities. The Grasslands and Fynbos biomes are the most sampled, with the Succulent Karoo the least. Most work focused on beetles, dragonflies, butterflies, ants, grasshoppers, and spiders. Few studies provide publicly available data (<2%) or indicate where reference collections were housed (31%). The main threats identified in South Africa are habitat loss and fragmentation through agriculture, pesticides, timber plantations, and invasive species. Most studies highlighted solutions, including greening of urban and agricultural landscapes, reduced pesticide use, and establishing conservation corridors. Research output has increased fourfold between 2000–2004 and 2020–2024, but the lack of long-term monitoring and data accessibility challenges means we cannot confidently assess population trends across most of South Africa’s insect diversity. South Africa’s extensive conservation entomology research should inform policy changes and public education. South Africa has demonstrated the capacity for large-scale insect conservation, yet we need to build on these achievements by establishing monitoring networks which are essential for sustaining ecological function and human well-being.

Seiridium is a genus of Sordariomycetes (Amphisphaeriales, Sporocadaceae), primarily known for species that cause cypress canker on Cupressaceae trees. However, most species in this genus have been reported from angiosperms, including many species in the native range of their hosts. Several unidentified Seiridium strains, collected > 20 years ago from Acacia mearnsii trees in eastern South Africa and southeastern Australia, were recently recovered from a collection of preserved cultures. We considered the phylogenetic position of these Seiridium strains and assessed their pathogenicity on A. mearnsii. Maximum likelihood analysis of three concatenated gene regions revealed four well-supported clades. Two closely related clades corresponded to Australian and South African origins, whereas two other clades representing South African isolates formed a monophyletic group with S. kartense, a species known from Eucalyptus cladocalyx on Kangaroo Island in Australia. Genome-wide average pairwise nucleotide identity and genetic differentiation analysis supported three species, including isolates considered conspecific with S. kartense and two that we consider to represent new species. These are described and named here as Seiridium mearnsii sp. nov. and Seiridium rouxiae sp. nov. Inoculations with South African isolates failed to produce evidence of pathogenicity. Seiridium species from A. mearnsii have likely been introduced into South Africa from Australia, along with the planting material used to establish A. mearnsii forestry.

Exotic crop production negatively affects native biodiversity and alters ecosystem functions and services. Cultivation of indigenous crops can mediate some biodiversity impacts, as these are often less intensively managed than exotic crops and they provide familiar niches for native organisms. Protea (Proteaceae), a floricultural crop with high economic value and ecological significance, is harvested within both natural and cultivated systems in South Africa. A multitude of organisms are intimately involved in Protea ecology, but many are also pests and pose significant phytosanitary risks. Here we evaluated the impact of Protea cultivation on the diversity of mites associated with inflorescences, infructescences, and the rhizosphere in the Greater Cape Floristic Region biodiversity hotspot of South Africa. Natural sites harboured higher mite diversity than cultivated sites, although this was only significant for those mites associated with the rhizosphere or when Protea crops were intensively managed. Mite community assemblage composition differed between different management types, localities, and niches. Management actions had little effect on mite assemblage composition in inflorescences and infructescences, likely due to continuous long-distance colonisation from natural areas via pollinators. In contrast, mite assemblages associated with the rhizosphere were highly impacted in all cultivated sites. These results indicate that indigenous crops can sustain substantial above-ground native mite biodiversity, but ecologically important soil assemblages may be severely impacted. Current field-based management strategies are not effective in controlling mite assemblages within Protea inflorescences, posing significant phytosanitary risks.

Worldwide introductions of non-native bark and ambrosia beetles (Coleoptera: Scolytinae) are increasing, with several species now capable of attacking living trees and introducing pathogenic fungi having been recorded in naïve habitats. Here we provide the first record of the exotic Amasa parviseta Knížek & Smith 2024 in continental Africa, based on four specimens collected across the Western Cape province of South Africa. This species is known to primarily colonise stressed or dying Eucalyptus and other Myrtaceae species. While no impacts have thus far been documented locally on commercially grown Eucalyptus, the species’ known ability to vector pathogenic fungi in other regions highlights its potential threat to not only South Africa’s commercial forestry industry but also its native species of Myrtaceae. We recommend targeted monitoring of this non-invasive species and investigations into its symbiotic fungi for potential phyto-pathogenicity. The discovery of this potentially harmful exotic species in South Africa underscores the importance of ongoing surveillance for non-native scolytine beetles to ensure early detection, proper risk assessment, and phytosanitary interventions to prevent establishment and mitigation of possible negative impacts.

Plant–herbivore interactions are important for almost all terrestrial ecosystems, but little is known about how herbivory and the specialization of these interactions change with the resource availability provided by host plant communities and time since disturbance. In fire-prone scrublands of the South African Cape Floristic Region, we studied interaction networks between 20 Protea shrub species and ten herbivorous insect species that consume seeds inside Protea cones during their larval stage. We studied these interactions at 18 sites that differed widely in plant resource availability (protea cone mass per hectare) and time since the last fire event. We sampled 1173 protea cones, identified the herbivores in each cone, and calculated herbivory rate (the proportion of infested cones), herbivore diversity (herbivore species richness and Shannon diversity), the number of host plant species per herbivore species (insect generality), the number of herbivore species per host plant species (plant vulnerability), as well as niche overlap among insect and plant species for each site. We found that most herbivore species interacted with the majority of Protea species. Herbivory rate and herbivore diversity were not affected by site-level resource availability or time since fire. Surprisingly, specialization of plant–herbivore interactions at the community level was independent of the environmental gradients studied, suggesting that the mechanisms structuring the interactions in this plant–herbivore system were independent of the environmental context. This finding suggests coupled community dynamics of protea plants and the insect herbivores feeding inside their cones in South African fynbos ecosystems.

Tree-planting is increasingly being promoted for urban greening, carbon sequestration, and to enhance biodiversity. However, poorly planned and executed tree-planting schemes can inadvertently contribute to biological invasions with detrimental effects on local ecosystems, economies, and human well-being. Therefore, sustainable, rigorous, repeatable, and transparent species selection strategies are needed. We developed a strategic decision protocol for identifying tree taxa suitable for planting schemes, using a multi-criterion approach that integrates national lists of regulated invasive plant species, global evidence of invasiveness, and susceptibility to key pests. Using the Polyphagous Shot Hole Borer (PSHB) invasion in the City of Cape Town, South Africa as a case study, we illustrate the protocol’s application and potential for informing planting decisions. 444 tree taxa currently planted in Cape Town were assessed. Of these, 85 are regulated nationally as invasive species (and are prohibited from use), while 49 met all suitability criteria and were identified as candidates for a planting list (i.e., a safe list). This protocol provides evidence-based guidance for tree-planting to mitigate the risk of tree invasions and to reduce the spread and impact of associated pests and pathogens. This protocol is replicable and adaptable for use in other regions and can support environmental planners and managers in making informed decisions to safeguard ecosystems and optimise ecosystem services (e.g., which trees to plant in restoration initiatives).

The polyphagous shot hole borer (PSHB, Euwallacea fornicatus) has invaded multiple countries, including South Africa. Along with its fungal mutualist, PSHB has caused the death of a wide range of tree species. Unmitigated costs of invasion in South Africa are estimated to be high. This study consisted of a 26-month PSHB monitoring programme using baited traps in an urban-agricultural fringe setting in the Western Cape province, focusing on revealing the factors most important to flight activity, beetle abundance, and infestation severity. It also tested the validity of felling infested trees as a management option to reduce beetle numbers (propagule pressure). More than half of the 94 study plots evaluated had PSHB-infested trees. Beetle flight activity was highest in summer and negligible in winter, with flight activity being positively correlated with temperature, beetle developmental degree days and beetle flight hours. The surrounding abundance of infested hosts was positively correlated with beetle abundance and infestation levels, though “saturation” in the infestation of a focal host tree may be a deterrent to dispersing beetles. Trees in plots that experience water stress (seasonal flooding) had higher dispersing beetle abundance and infestation levels, suggesting that tree stress might play a role in attracting beetles or making trees more vulnerable to infestation. Beetle activity during tree felling echoed the overall seasonal trend, and higher numbers of dispersing beetles on the day of tree felling in summer suggest that felling activities should best be conducted in winter. For three host tree species, infestation severity increased with decreasing tree size, which may be due to larger trees having thicker bark or other better defence systems. This study provides insight into the ecology of PSHB in this region of South Africa, which is important for developing monitoring and management strategies.

The Polyphagous Shot Hole Borer (PSHB; Euwallacea fornicatus, Coleoptera: Curculionidae: Scolytinae) is an invasive and destructive tree pest. To assess whether thermal acclimation influences E. fornicatus locomotion performance (i.e., induced plastic responses) that may influence invasion potential, beetles were acclimated to three temperatures (18 °C, 25 °C, and 32 °C), and four locomotion traits were measured across six temperatures (13 °C, 18 °C, 23 °C, 28 °C, 33 °C and 38 °C) per acclimation group to construct thermal performance curves, capturing critical thermal minimum (Tmin), critical thermal maximum (Tmax), thermal breadth (Tbr), optimal performance rate (Umax). Substantial plasticity of performance curves was found in E. fornicatus. Generally, cold (18 °C) acclimation increased the thermal range of several locomotor performance traits without affecting performance levels, thereby supporting the colder-is-better hypothesis. To assess the consequences of these plastic responses, using the thermal performance curves established here, movement rates of E. fornicatus in an at-risk orchard area in South Africa were predicted across seasons while considering artificial warm and cold spells. Cold-acclimated beetles exhibited the highest cumulative distance traveled in both summer and winter, while warm-acclimated beetles had the lowest. Therefore, short-term thermal variation significantly influenced E. fornicatus locomotion performance, with cold acclimation notably improving dispersal across a wide range of thermal conditions. These findings highlight the importance of considering recent thermal history when predicting E. fornicatus invasion potential. By integrating these data with microclimatic conditions and functional models, this study offers valuable insights for predicting E. fornicatus spread, informing targeted management strategies, and refining spatially explicit risk assessments to mitigate the impacts of this invasive pest.

In this study we assessed how an invasive tree (Acacia mearnsii) and an ecologically equivalent native species (Virgilia divaricata) interact with their insect pests and fungal pathogens in sympatric populations along forest edges in the Cape Floristic region of South Africa. We determined how insect herbivore abundance and fungal disease development differ between the two species across a moisture gradient and whether observed differences can be explained by moisture availability and/or plant nutrient levels. The two host plants had similar foliar nutrient content, but measurements of 612C / 613C isotope ratios in leaves indicated that only the native plant experienced drought stress at drier sites. The degree of disease development after tree wounding was similarfor both species and was not correlated with soil moisture content in either species. As predicted by the biotic release hypothesis, herbivore numbers were significantly higher on the native plant. Herbivore numbers on A. mearnsii were unaffected by moisture availability, but herbivore numbers on V. divaricata increased at drier sites. Consequently, under conditions of increased drought, V. divaricata may experience higher levels of drought stress than the invasive A. mearnsii and may suffer from increased insect herbivory, rendering it a weaker competitor. Herbivore abundance and disease development were significantly influenced by plant nutrient content for A. mearnsii, but not for V. divaricata. Relatively nutrient-poor A. mearnsii trees experienced higher herbivore loads but slower disease development than nutrient-rich trees. Therefore, the susceptibility of A. mearnsii seems to be determined by plant nutrient levels, a factor that varies independentlyfrom water availability.

The polyphagous shot hole borer (PSHB; Euwallacea fornicatus), is an invasive ambrosia beetle and poses a significant threat to a wide range of tree species globally. Despite its potential impact, research on the beetle's spread and impacts in natural ecosystems remains limited. This study examines the interactions between PSHB and native forest ecosystems in two regions in South Africa. Over 5 years, PSHB invaded all but one forest type with colonization being recorded on numerous native tree species, often resulting in severe infestations and sometimes mortality. Many tree species and families had higher than expected infestation rates. An increase in PSHB-attacked trees and infestation severity was observed over the course of the study with trees having a 7.5

Naturally fragmented indigenous forests in the southern Cape of South Africa are particularly understudied in terms of beetle diversity. This study therefore aimed to determine whether southern Afrotemperate forest dung and carrion beetle diversity differs between continuous forest and naturally occurring forest patches. Beetles were sampled from sixteen sites: eight within a continuous forest and eight within forest patches using three baited pitfall trap types (carrion, pig dung, and carrion plus pig dung). A total of 500 individual beetles were sampled from forest patches and 272 individual beetles from continuous forests. Forest patches supported a richer diversity of dung and carrion beetles (8 spp.) compared to continuous forests (3 spp.), and also supported a higher abundance of generalist species. More individuals and species were collected with a combination of carrion and pig dung while no species exclusively preferred the carrion bait. Body size of two beetle species differed between forest patches and continuous forests, though the pattern was contradictory. The intermediate disturbance hypothesis may explain these results, as forest patches often have human- or animal-made paths that traverse them, increasing their permeability. Predictably, the provision of ecosystem services is thus maintained, or even enhanced, in forest patches, highlighting their conservation significance.

Widdringtonia is a genus of native southern African Cupressaceae trees comprising two species that occur in the mountains of the Western Cape province, South Africa. Widdringtonia cedarbergensis has a localised distribution and is critically endangered, while W. nodiflora is widespread and common. Little is known regarding the biotic associations of these trees. The aim of this study was, consequently, to identify bark beetles (Curculionidae: Scolytinae) and their associated fungi on Widdringtonia species in the Western Cape. Bark beetles were collected from infested W. cedarbergensis at three different locations in the Cederberg and from W. nodiflora at one site on the Franschhoek Pass. Beetle identification was based on morphology and sequence data of the COI gene region. Fungi were isolated from beetles, their frass and the walls of their tunnels and grouped according to morphology. Morphogroups were identified by sequencing the ITS region of representative isolates. Four phylogenetically closely related bark beetle species residing in the genus Lanurgus (Micracidini) were identified, three from W. cedarbergensis stem sections, twigs and cones, respectively, and one from W. nodiflora stems. Of these, only the W. cedarbergensis twig beetle is of a previously described species and is currently known as Diplotrichus widdringtoniae. Piskurozyma sp. (Tremellomycetes) and Yamadazyma sp. (Saccharomycetes) yeasts were most closely associated with D. widdringtoniae (Lanurgus sp. 1) and Lanurgus sp. 2 beetles, whereas Geosmithia spp. (Sordariomycetes) had a strong association with Lanurgus sp. 3 and Lanurgus sp. 4. This is the first comprehensive report of bark beetles and their associated fungi infesting Widdringtonia.

Fusarium euwallaceae, vectored by the paninvasive polyphagous shot hole borer beetle (Euwallacea fornicatus), is an emerging threat to trees globally. Proven pathogenic to cultivated deciduous fruits in South Africa, it recently has been isolated from cultivated European (Olea europaea subsp. europaea) and native African (Olea europaea subsp. cuspidata) olive. This potentially threatens both commercial production and native species conservation. However, pathogenicity to these trees is unknown. Three isolates were used in pathogenicity trials of F. euwallaceae towards cultivated European and African olives. Fusarium euwallaceae caused significantly longer lesions than the controls in vascular tissues of inoculated European olive trees, whereas no difference was observed for African olive. We therefore report for the first time that F. euwallaceae is pathogenic to cultivated European olive but not to African olive. As this fungus occludes affected xylem tissues, and thus water flow, olive fruit and oil production might be hampered during droughts, which are predicted to increase in severity and frequency in the main region olives are planted in in South Africa.

The polyphagous shot hole borer (PSHB), Euwallacea fornicatus Eichhoff (Coleoptera: Curculionidae, Scolytinae), is a significant tree-killing pest recently introduced into South Africa. Many native trees in urban settings are susceptible to infestation, but the presence of PSHB in natural ecosystems is unstudied. The presence and drivers of PSHB colonization in 1682 trees of 68 species were evaluated in 51 plots across a native Afrotemperate forest complex in South Africa. Breeding colonies of PSHB were found in six native species (breeding hosts). An additional 11 species did not contain PSHB colonies but hosted its mutualistic fungus Fusarium euwallaceae Freeman et al. (Hypocreales: Nectriaceae). Invasibility increased when plots were closer to the urban infestation border, further away from surface water, and when containing a larger number of breeding hosts. Invasibility decreased with an increase in tree species richness. Polyphagous shot hole borers were found in climax forest distant to urban areas at sites frequented by tourists. The severity of infestation of trees increased with an increase in host diameter, breeding host abundance, and infested tree abundance. Probability of infestation increased with an increase in the number of infested trees. Infested trees were not spatially clumped. Instead, PSHB preferentially selected eight of the 17 native host species. And the data suggest that larger trees of these species may be more susceptible to PSHB. Eight species were infested at random and two were infested seemingly accidentally. Infestations increased more rapidly on larger trees and on those surrounded by a high abundance of breeding hosts. This study confirms that Afrotemperate forests are highly susceptible to invasion by PSHB. Direct anthropogenic impact had no discernible effect on infestations, but humans aided spread of PSHB to distant sites. Halting movement of contaminated wood is important. Management of PSHB should focus on highly infested areas and trees as these increase the likelihood of further and more severe infestations.

Sub-cortical beetles and mites contribute to tree mortality by creating wounds and by spreading potential pathogens. Here we elucidate associations between sub-cortical beetles, mites, and ophiostomatoid fungi from trees in Afromontane forests in South Africa. Bark and wood samples were collected from native tree species and exotic Pinus radiata and Acacia mearnsii that showed signs of sub-cortical beetle activity, or from wounds on storm-damaged trees. Ophiostomatoid fungi, a group that contains numerous tree pathogens, were isolated from beetles that emerged from samples, their galleries, phoretic mites on these beetles, and from wounds and wound-associated mites. Fungal isolates were identified using multiple DNA markers. Twenty sub-cortical beetle, 22 mite and 16 ophiostomatoid fungal species were recovered from only a few native and exotic host tree species. Three fungal species are likely undescribed despite increased focus on this ecologically and economically important group worldwide. Significantly, some mites and fungi were isolated from native and non-native hosts. Wound-associated fungi and mites were less host-specific than sub-cortical beetle-associated taxa. We highlight the rich and still unexplored symbioses between sub-cortical beetles, mites, and ophiostomatoid fungi in Afromontane forests and provide a foundation for future studies on the ecology of these important organisms.

Benefits provided by urban trees are increasingly threatened by non-native pests and pathogens. Monitoring of these invasions is critical for the effective management and conservation of urban tree populations. However, a shortage of professionally collected species occurrence data is a major impediment to assessments of biological invasions in urban areas. We applied data from iNaturalist to develop a protocol for monitoring urban biological invasions using the polyphagous shot hole borer (PSHB) invasion in two urban areas of South Africa. iNaturalist records for all known PSHB reproductive host species were used together with data on localities of sites for processing plant biomass to map priority monitoring areas for detecting new and expanding PSHB infestations. Priority monitoring areas were also identified using the distribution of Acer negundo , a highly susceptible host that serves as a sentinel species for the detection of PSHB infestations. iNaturalist data provided close to 9000 observations for hosts in which PSHB is known to reproduce in our study area (349 of which were A. negundo ). High-priority areas for PSHB monitoring include those with the highest density of PSHB reproductive hosts found close to the 140 plant biomass sites identified. We also identified high-priority roads for visual and baited trap surveys, providing operational guidance for practitioners. The monitoring protocol developed in this study highlights the value of citizen or community science data in informing the management of urban biological invasions. It also advocates for the use of platforms such as iNaturalist as essential tools for conservation monitoring in urban landscapes.