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Australian Acacia species are among the most important trees planted for wood and pulp production in several African countries, including Ethiopia. In 2020, symptoms of a serious shoot and leaf rust disease were observed on black wattle (Acacia mearnsii De Wild.) trees across the three main wattle growing regions of Ethiopia. The aim of this study was to describe the disease and identify its causal agent based on morphological characteristics as well as DNA sequence data for the ITS and LSU regions of ribosomal DNA. Here we report for the first time, the presence of the wattle rust pathogen, Uromycladium acaciae, in Ethiopia. [ABSTRACT FROM AUTHOR]

A serious new disease of Eucalyptus was detected in South African plantations of these trees during the summer of 2021/2022. The first symptoms are minute dark spots on young leaves, petioles and shoots, becoming scab-like as the spots age. On highly susceptible Eucalyptus genotypes, leaves and shoots can become malformed leading to a 'feathering' appearance in the tree canopies and in the case of heavy infections, leaf and shoot death occur. Isolations made directly from developing scabs resulted in slow-growing cultures. These were identified, based on phylogenetic analyses of DNA sequence data for the ITS, LSU, TEF1 and RPB2 regions, as a novel species of Elsinoe (Elsinoaceae, Myriangiales), described here as E. masingae. Inoculations of an Eucalyptus grandis  ×  Eucalyptus nitens hybrid variety produced the same symptoms as those observed under natural conditions and the pathogen could be re-isolated from the emerging lesions. Elsinoe masingae is closely related to, but clearly distinct from, the recently described Elsinoe necatrix that causes a serious scab and shoot malformation disease on Eucalyptus in Indonesia. Field surveys revealed significant variation in the susceptibility of different Eucalyptus genotypes, with the most severely affected genotypes including an E. grandis  ×  nitens and an E. grandis  ×  urophylla hybrid variety and E. grandis. The disease has also been observed on Eucalyptus amplifolia and on Eucalyptus dunnii , which had mild infections. The observed variation in susceptibility of Eucalyptus planting stock should provide opportunities to avoid serious damage because of scab caused by E. masingae in the future. [ABSTRACT FROM AUTHOR]

Aim: Spreading infectious diseases associated with introduced pathogens can have devastating effects on native biota and human livelihoods. We analyse the global distribution of 100 major alien fungal and oomycete pathogens with substantial socio‐economic and environmental impacts and examine their taxonomy, ecological characteristics, temporal accumulation trajectories, regional hot‐ and coldspots of taxon richness and taxon flows between continents. Location: Global. Taxon: Alien/cryptogenic fungi and fungus‐like oomycetes, pathogenic to plants or animals. Methods: To identify over/underrepresented classes and phyla, we performed Chi2 tests of independence. To describe spatial patterns, we calculated the region‐wise richness and identified hot‐ and coldspots, defined as residuals after correcting taxon richness for region area and sampling effort via a quasi‐Poisson regression. We examined the relationship with environmental and socio‐economic drivers with a multiple linear regression and evaluated a potential island effect. Regional first records were pooled over 20‐year periods, and for global flows the links between the native range to the alien regions were mapped. Results: Peronosporomycetes (Oomycota) were overrepresented among taxa and regional taxon richness was positively correlated with area and sampling effort. While no island effect was found, likely due to host limitations, hotspots were correlated with human modification of terrestrial land, per capita gross domestic product, temperate and tropical forest biomes, and orobiomes. Regional first records have increased steeply in recent decades. While Europe and Northern America were major recipients, about half of the taxa originate from Asia. Main Conclusions: We highlight the putative importance of anthropogenic drivers, such as land use providing a conducive environment, contact opportunities and susceptible hosts, as well as economic wealth likely increasing colonisation pressure. While most taxa were associated with socio‐economic impacts, possibly partly due to a bias in research focus, about a third show substantial impacts to both socio‐economy and the environment, underscoring the importance of maintaining a wholescale perspective across natural and managed systems. [ABSTRACT FROM AUTHOR]

Several economically important pathogens, including species of Chrysoporthe, pose a threat to the rapidly expanding eucalypt plantation industry in Southeast Asia. During 2019 disease surveys in Riau and Kalimantan (Indonesia), cankers were observed on eucalypt trees and a collection of fungal isolates was obtained from them. The aim of this study was to confirm the identity of the isolates and to evaluate their relative pathogenicity on different eucalypt clones. Using the DNA sequence data based on the internal transcribed spacer (ITS) region of the ribosomal DNA and two regions of the β-tubulin gene (TUB1 and TUB2), 31 fungal isolates were identified as C. deuterocubensis. Pathogenicity trials showed that C. deuterocubensis isolates differed in their pathogenicity and that different eucalypt genotypes differed in their susceptibility to the pathogen. These results will provide valuable information to reduce the threat of stem canker to future eucalypt plantation development. [ABSTRACT FROM AUTHOR]