Arthropod-mediated dispersal of pathogens is known in many cropping systems but has never been demonstrated for grapevine trunk disease pathogens. Arthropods from vineyards were screened for the presence of pathogens associated with Petri disease and esca using cultural and molecular techniques. The ability of the most abundant pathogen-carrying species to inoculate healthy grapevine vascular tissues was also determined. Millipedes and ants were allowed to associate with a DsRed- Express-transformed Phaeomoniella chlamydospora, after which they were exposed to freshly pruned healthy grapevines under controlled conditions and wounds were monitored for subsequent infection. In addition, the possibility of millipede excreta, commonly found on pruning wounds in the field, to act as inoculum source was determined. A diverse arthropod fauna was associated with declining grapevines and many of these carried trunk disease pathogens. However, spiders, the ant Crematogaster peringueyi, and the millipede Ommattoiulus moreleti were the most abundant pathogen carriers. The ant and millipede species fed on pruning wound sap and effectively transmitted trunk disease pathogens. Millipede excreta contained viable spores of Phaeomoniella chlamydospora and may serve as an inoculum source. Numerous arthropods, including beneficial predators, are potential vectors of grapevine trunk disease pathogens. Our results highlight the need for an integrated approach, including targeted management of ants and millipedes at the time of pruning, to limit the spread of grapevine trunk diseases.

Nineteen Phaeoacremonium species are currently known in South Africa. These have been reported from grapevines, fruit trees, fynbos twig litter and arthropods. In other countries some of these Phaeoacremonium species are also known from hosts such as European olive, quince and willow that commonly occur in the Western Cape Province of South Africa, where most South African records of Phaeoacremonium have been made. The aim of this study was to investigate the species diversity and host-range of Phaeoacremonium in the Western Cape Province of South Africa by characterising 156 isolates collected from 29 woody hosts. Phylogenetic analyses of combined actin and beta-tubulin datasets allowed for the identification of 31 species among the 156 isolates, including 13 new species and 3 known species that had not been recorded in South Africa previously. The new Phaeoacremonium species include P. album, P. aureum, P. bibendum, P. gamsii, P. geminum, P. junior, P. longicollarum, P. meliae, P. oleae, P. paululum, P. proliferatum, P. rosicola and P. spadicum. All previous records of P. alvesii in South Africa were re-identified as P. italicum, but both species were recovered during this survey. A total of 35 described Phaeoacremonium species are now known from South Africa, more than double the number reported from any other country. This high diversity reflects the high diversity of indigenous flora of the Cape Floral Region, a biodiversity hotspot mainly situated in the Western Cape Province. Paraphyly and incongruence between individual phylogenies of the actin and beta-tubulin regions complicated species delimitation in some cases indicating that additional phylogenetic markers should be investigated for use in Phaeoacremonium phylogenies to prevent misidentifications and the introduction of vague species boundaries.

Recent studies in grape-growing areas including Australia, California, and Spain have revealed an extensive diversity of Diatrypaceae species on grapevines showing dieback symptoms and cankers. However, in South Africa, little is known regarding the diversity of these species in vineyards. The aim of this study was, therefore, to identify and characterize Diatrypaceae species associated with dieback symptoms of grapevine in South Africa. Isolates were collected from dying spurs of grapevines aged 4 to 8 years old, grapevine wood showing wedge-shaped necrosis when cut in cross section as well as from perithecia on dead grapevine wood. The collected isolates were identified based on morphological characters and phylogenetic analyses of the internal transcribed spacer region (ITS) and β-tubulin gene. Seven Diatrypaceae species were identified on grapevine, namely Cryptovalsa ampelina, C. rabenhorstii, Eutypa consobrina, E. lata, E. cremea sp. nov., Eutypella citricola, and E. microtheca. The dying spurs yielded the highest diversity of species when compared with the wedge-shaped necrosis and/or perithecia. C. ampelina was the dominant species in the dying spurs, followed by E. citricola, whereas E. lata was the dominant species isolated from the wedge-shaped necroses and perithecia. These results confirm E. lata as an important grapevine canker pathogen in South Africa, but the frequent association of C. ampelina with spur dieback suggests that this pathogen plays a more prominent role in dieback than previously assumed. In some cases, more than one species were isolated from a single symptom, which suggests that interactions may be occurring leading to decline of grapevines. C. rabenhorstii, E. consobrina, E. citricola, E. microtheca, and E. cremea are reported for the first time on grapevine in South Africa.

Stone fruit trees (Prunus spp.) are economically important fruit trees cultivated in South Africa. These trees are often grown in close proximity to vineyards and are to a large extent affected by the same trunk disease pathogens as grapevines. The aim of the present study was to determine whether stone fruit trees are inhabited by Diatrypaceae species known from grapevines and whether these trees could act as alternative hosts for these fungal species. Isolations were carried out from symptomatic wood of Prunus species (almond, apricot, cherry, nectarine, peach, and plum) in stone fruit growing areas in South Africa. Identification of isolates was based on phylogenetic analyses of the internal transcribed spacer region and β-tubulin gene. Forty-six Diatrypaceae isolates were obtained from a total of 380 wood samples, from which five species were identified. All five species have also been associated with dieback of grapevine. The highest number of isolates was found on apricot followed by plum. No Diatrypaceae species were isolated from peach and nectarine. Eutypa lata was the dominant species isolated (26 isolates), followed by Cryptovalsa ampelina (7), Eutypa cremea (5), Eutypella citricola (5), and Eutypella microtheca (3). First reports from Prunus spp. are E. cremea, E. citricola, and E. microtheca. Pathogenicity tests conducted on apricot and plum revealed that all these species are pathogenic to these hosts, causing red-brown necrotic lesions like those typical of Eutypa dieback on apricot.

Diaporthe species cause Phomopsis cane and leaf spot as well as Phomopsis dieback on grapevines. Symptoms of Phomopsis dieback have increasingly been observed over the past few years. In order to assess the current status of Diaporthe on grapevines in the Western Cape Province of South Africa, isolations were made from dormant grafted nursery vines, dormant rootstock canes, and dying or dead spurs of field vines. Cultures identified as Diaporthe based on morphological features were further identified to species level by sequencing the internal transcribed spacers (ITS) 1 and 2 and 5.8S rRNA and, for a representative subsample of isolates, the partial beta-tubulin (tub2) and translation elongation factor 1-alpha (EF1-α) genes. Phylogenetic analysis of the combined ITS, tub2, and EF1-α data revealed nine Diaporthe species associated with grapevines during this survey. One of these represents a new species, D. nebulae sp. nov., and three other species, namely D. novem, D. cynaroidis, and D. serafiniae, are reported on grapevines in South Africa for the first time. Species-specific primers were designed for PCR identification of D. ampelina, D. ambigua, and D. foeniculina. Pathogenicity studies conducted on detached grapevine shoots indicated D. ampelina, D. novem, and D. nebulae sp. nov. as the most virulent species.

A recent olive trunk disease survey performed in the Western Cape Province, South Africa, identified several fungi associated with olive trunk disease symptoms, including species of Basidiomycota, Botryosphaeriaceae, Coniochaetaceae, Calosphaeriaceae, Diaporthaceae, Diatrypaceae, Phaeomoniellaceae, Phaeosphaeriaceae, Symbiotaphrinaceae, Togniniaceae, and Valsaceae. Many of the species recovered had not yet been reported from olive trees; therefore, the aim of this study was to determine their pathogenicity toward this host. Pathogenicity tests were first conducted on detached shoots to select virulent isolates, which were then used in field trials. During field trials, 2-year-old olive branches of 15-year-old trees were inoculated by inserting colonized agar plugs into artificially wounded tissue. Measurements were made of the internal lesions after 8 months. In total, 58 isolates were selected for the field trials. Species that formed lesions significantly larger than the control could be considered as olive trunk pathogens. These included Biscogniauxia rosacearum, Celerioriella umnquma, Coniochaeta velutina, Coniothyrium ferrarisianum, isolates of the Cytospora pruinosa complex, Didymocyrtis banksiae, Diaporthe foeniculina, Eutypa lata, Fomitiporella viticola, Neofusicoccum stellenboschiana, Neofusicoccum vitifusiforme, Neophaeomoniella niveniae, Phaeoacremonium africanum, Phaeoacremonium minimum, Phaeoacremonium oleae, Phaeoacremonium parasiticum, Phaeoacremonium prunicola, Phaeoacremonium scolyti, Phaeoacremonium spadicum, Pleurostoma richardsiae, Pseudophaeomoniella globosa, Punctularia atropurpurascens, Vredendaliella oleae, an undescribed Cytospora sp., Geosmithia sp., two undescribed Neofusicoccum spp., and four Xenocylindrosporium spp. Pseudophaeomoniella globosa can be regarded as one of the main olive trunk pathogens in South Africa because of its high incidence from olive trunk disease symptoms in established orchards and its high virulence in pathogenicity trials.