Future danger posed by fungi in the Ophiostomatales when encountering new hosts

The Ophiostomatales contain pathogens that threaten forests world-wide. Global trade increases encounters with new hosts, with potential devastating consequences. We assessed the danger posed by the movement of Ophiostomatales between different host trees in South Africa. We tested the pathogenicity of five fungal species from native South African trees, and three from exotic trees, on various native and exotic trees. To evaluate the potential of fungi to move to new hosts, we investigated the strength of their associations with arthropod vectors. Results indicate that many fungal species are pathogens of newly encountered and distantly-related hosts. Encounters of pathogens with new hosts are less likely when host plants are distantly related, and outside the host range of boring beetle vectors, which also reduces the chances of vectoring by phoretic mite associates. However, pathogens associated with numerous mite species and wounds are more likely to encounter new hosts and pose future threats.The authors thank the DST/NRF Centre of Excellence in Tree Health Biotechnology (CHTB) for financial support and the South African National Parks Board (SANPARKS) and Western Cape Nature Conservation Board for issuing the necessary collecting permits.http://www.journals.elsevier.com/fungal-ecology2017-08-31hb2016Microbiology and Plant Patholog

A serious canker disease caused by Immersiporthe knoxdaviesiana gen. et sp. nov. (Cryphonectriaceae) on native Rapanea melanophloeos in South Africa

Recent disease surveys in the Western Cape province of South Africa have revealed a previously unknown and serious stem canker disease on native Rapanea melanophloeos (Myrsinaceae, Ericales) trees. Cankers commonly result in the death of branches or entire stems. Fruiting structures typical of fungi in the Cryphonectriaceae were observed on the surfaces of cankers. In this study, the fungus was identified and its pathogenicity to R. melanophloeos was tested. Multigene phylogenetic analyses based on DNA sequences of the partial LSU gene, ITS region of the nuclear ribosomal DNA gene and two regions of the β-tubulin (BT) gene, showed that the fungus represents a formerly undescribed genus and species in the Cryphonectriaceae. The fungus was also morphologically distinct from other genera in this family. Inoculation trials showed that the fungus described here as Immersiporthe knoxdaviesiana gen. et sp. nov. is an aggressive pathogen of R. melanophloeos trees.DST/NRF Centre of Excellence in Tree Health Biotechnology (CHTB)http://www.wiley.com/bw/journal.asp?ref=0032-0862hb201

Unseen fungal biodiversity and complex inter- organismal interactions in Protea flower heads

A unique microbiome occurs within the flower heads of various Protea species endemic to Africa. These include two lineages of ophiostomatoid fungi, Knoxdaviesia (Microascales) and Sporothrix (Ophiostomatales), that have members occurring exclusively in this environment and that rely on mites as their primary mode of spore dissemination. The mites, in turn, attach to the bodies of Protea-pollinating beetles and the beaks and bodies of birds for long-distance movement, establishing a hierarchical dispersal network for the ophiostomatoid fungi. This inter-organismal network is highly successful, achieving fungal dispersal over vast distances. Multiple species of fungi, mites and bacteria have been described from this unique niche over the past four decades. The intricacies of their symbiotic interactions continue to be unravelled. This review covers all current knowledge of the “distinctly African” Protea-ophiostomatoid fungus environment and illustrates the depth of a fascinating unseen fungal biodiversity niche.The South African Department of Science and Innovation (DSI), the National Research Foundation (NRF) Centre of Excellence in Plant Health Biotechnology (CPHB) and the Tree Protection Co-operative Program (TPCP).http://www.elsevier.com/locate/fbram2024BiochemistryGeneticsMicrobiology and Plant PathologySDG-15:Life on lan

Detection of Fusarium euwallaceae and its vector Euwallacea fornicatus on pear (Pyrus communis) and in deciduous fruit orchards in South Africa

We present the first report of Fusarium euwallaceae and its ambrosia beetle vector Euwallacea fornicatus in deciduous fruit tree orchards in South Africa. Fusarium euwallaceae, is shown to be pathogenic to pear (Pyrus communis) and the beetle can establish viable colonies in this host.Hortgro. Open access funding provided by Stellenbosch University.https://link.springer.com/journal/13314hj2024BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyNon

Lessons from a major pest invasion : the polyphagous shot hole borer in South Africa

CITATION: Paap, T. et al. 2020. Lessons from a major pest invasion : the polyphagous shot hole borer in South Africa. South African Journal of Science, 116(11/12):8757, doi:10.17159/sajs.2020/8757.The original publication is available at https://sajs.co.zaThe arrival and establishment of invasive forest pests can cause devastating environmental damage and great economic impact. For example, the cost over the past decade of dealing with the arrival of a single invasive beetle in the USA, the emerald ash borer (Agrilus planipennis), is estimated at more than USD10 billion.1 Originating from Asia, this beetle has killed hundreds of millions of native ash trees since it became established in the USA. However, this beetle is but one of hundreds of invasive insect pests that impact forests in the USA, and that contribute to a global tree health crisis caused by invasive insects and pathogenic microorganisms.2-4 South Africa is no different from other countries and is experiencing an increasing rate of introductions of damaging forest pests.5,6 These invasions are largely unintentional and are a by-product of globalisation and increasing global trade.7,8 The movement of living plants and plant products, including untreated wood packaging materials (i.e. pallets, dunnage and crating), is known to be a major pathway for these pests.9,10 For clarification, in this commentary we use the terms ‘insect’ and ‘pathogen’ to distinguish between the two types of organisms, although we also use the general term ‘pest’ to refer to both groups. The term ‘invasive pest’ is used for introduced species that, in addition to maintaining a self-sustaining population, show evidence of spread and impact.https://sajs.co.za/article/view/8757Publisher's versio

Bark and ambrosia beetles (Curculionidae : Scolytinae), their phoretic mites (Acari) and associated Geosmithia species (Ascomycota : Hypocreales) from Virgilia trees in South Africa

Bark and ambrosia beetles are ecologically and economically important phloeophagous insects that often have complex symbiotic relationships with fungi and mites. These systems are greatly understudied in Africa. In the present study we identified bark and ambrosia beetles, their phoretic mites and their main fungal associates from native Virgilia trees in the Cape Floristic Region (CFR) of South Africa. In addition, we tested the ability of mites to feed on the associated fungi. Four species of scolytine beetles were collected from various Virgilia hosts and from across the CFR. All were consistently associated with various Geosmithia species, fungi known from phloeophagous beetles in many parts of the world, but not yet reported as Scolytinae associates in South Africa. Four beetle species, a single mite species and five Geosmithia species were recovered. The beetles, Hapalogenius fuscipennis, Cryphalini sp. 1 and Scolytoplatypus fasciatus were associated with a single species of Elattoma phoretic mite that commonly carried spores of Geosmithia species. Liparthrum sp. 1 did not carry phoretic mites. Similar to European studies, Geosmithia associates of beetles from Virgilia were constant over extended geographic ranges, and species that share the same host plant individual had similar Geosmithia communities. Phoretic mites were unable to feed on their Geosmithia associates, but were observed to feed on bark-beetle larvae within tunnels. This study forms the first African-centred base for ongoing global studies on the associations between arthropods and Geosmithia species. It strengthens hypotheses that the association between Scolytinae beetles and dry-spored Geosmithia species may be more ubiquitous than commonly recognised.DST⁄NRF Centre of Excellence in Tree Health Biotechnology (CHTB)http://www.elsevier.com/locate/funbiohb201

Invasion of an Afrotemperate forest complex by the polyphagous shot hole borer beetle

DATA AVAILABILITY STATEMENT : The data that support the findings of this study are available from the corresponding author upon reasonable request.SUPPORTING INFORMATION : TABLE S1. List of tree species and their respective families found in all 51 monitoring plots. Summaries are presented for mean (± SE) diameter at breast height (cm), the percentage of trees of each species out of all trees of all species (dominance), polyphagous shot hole borer (PSHB) breeding host or not, the percentage of trees that were infested by PSHB, the percentage increase of infested trees from sampling period 1–4, and the percentage increase in the number of holes from sampling period 1–4. TABLE S2. All tree species found in 10 polyphagous shot hole borer (PSHB) monitoring plots set out at the George Botanical Garden's. Presented is the dominance (% of all trees encountered), the number of trees infested with PSHB (% of infested trees of that species), and the average diameter at breast height (cm) of each species encountered. TABLE S3. Test table showing sample size (n), χ2 statistic, P, and Yates correction P for the preferential colonization of polyphagous shot hole borer between tree species.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.Tree Protection Cooperative Programme (TPCP); Forestry and Agricultural Biotechnology Institute (FABI); South African Department of Environment, Forestry, and Fisheries (DEFF).http://www.wileyonlinelibrary.com/journal/eeahj2024BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and EntomologySDG-15:Life on lan

Restoration of invaded Cape Floristic Region riparian systems leads to a recovery in foliage-active arthropod alpha- and beta-diversity

The Cape Floristic Region of South Africa is a global biodiversity hotspot threatened by invasive alien plants (IAPs). We assessed the effect of plant invasions, and their subsequent clearing, on riparian arthropod diversity. Foliage-active arthropod communities were collected from two native and one invasive alien tree species. Alpha- and beta- diversity of their associated arthropod communities were compared between near pristine, Acacia-invaded and restored sites. Arthropod alpha-diversity at near pristine sites was higher than at restored sites, and was lowest at invaded sites. This was true for most arthropod taxonomic groups associated with all native tree species and suggests a general trend towards recovery in arthropod alpha-diversity after IAP removal. Overall, arthropod species turnover among sites was significantly influenced by plant invasions with communities at near pristine sites having higher turnover than those at restored and invaded sites. This pattern was not evident at the level of individual tree species. Although arthropod community composition was significantly influenced by plant invasions, only a few significant differences in arthropod community composition could be detected between restored and near pristine sites for all tree species and arthropod taxonomic groups. Assemblage composition on each tree species generally differed between sites with similar degrees of plant invasion indicating a strong turnover of arthropod communities across the landscape. Results further suggest that both arthropod alpha- and beta- diversity can recover after IAP removal, given sufficient time, but catchment signatures must be acknowledged when monitoring restoration recovery.The DST/NRF Centre of Excellence in Tree Health Biotechnologyhttp://link.springer.com/journal/108412017-02-28hb2016Microbiology and Plant Patholog

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

Numerous dead and dying individuals of the Western Cape endemic tree Virgilia oroboides (Fabaceae) were recently observed within a South African national botanical garden. Root-rot fungi and fungi symbiotic with bark beetles (Curculionidae; Scolytinae) from diseased trees were assessed for their respective roles in V. oroboides mortality. Disease progression was also monitored over 1 year. Fungi were isolated from surface sterilized bark and root samples from diseased trees and provisionally identified using data from the internal transcribed spacer regions (ITS1, ITS2), including the 5 8S rRNA gene (ITS). Pathogenicity of selected fungi towards V. oroboides was tested under field conditions. The pathogenicity of various bark beetle-associated Geosmithia (Hypocreales: Hypocreomycetidae) spp. from V. oroboides were similarly assessed. The only fungus consistently isolated from lesions on the roots and bark of declining V. oroboides, and never from healthy individuals, represented an undescribed Diaporthe (Diaporthales, Diaporthaceae) species that was characterized using molecular (using data from the ITS marker and part of the b-tubulin gene, TUB), cultural and morphological characters. It is an aggressive pathogen of V. oroboides, newly described here as Diaporthe virgiliae sp. nov. Trees of all ages are susceptible to this pathogen with subsequent bark beetle attack of mature trees only. All Geosmithia spp. from beetles and/or infected trees were nonpathogenic towards V. oroboides. Diaporthe virgiliae caused a severe decline in the health of the monitored V. oroboides population over a period of only 1 year and should be considered as a significant threat to these trees.DST/NRF Centre of Excellence in Tree Health Biotechnology (CHTB).http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-3059hb201