Ten important forest fungal pathogens: a review on their emergence and biology

Plant pathogenic fungi and fungus-like taxa (oomycetes) form part of the ecological makeup of healthy natural forest ecosystems. Some help to eliminate unhealthy trees, while others are essential for the conservation of plant species diversity, particularly soil-borne pathogens. However, many fungal pathogens also have devastating effects on forest ecosystems. Disease impacts are more profound when pathogens newly emerge and these can even wipe out an entire tree population. These organisms have developed a plethora of strategies to colonize and infect plants and there are several factors causing pathogens to emerge. Therefore, to prevent emerging diseases, a thorough understanding of the factors causing them is necessary. It is also important to have a comprehensive understanding of the mechanisms of disease development and propagation to design effective control measures. In this review, we describe the phenomenon of emerging and reemerging pathogens by exemplifying ten important recently emerged forest pathogenic fungi and fungus-like taxa, namely, Ophiostoma novo-ulmi, Ceratocystis fimbriata, Fusarium circinatum, Hymenoscyphus fraxineus, Phyllosticta citricarpa, Neonectria faginata, Sphaerulina musiva, Phytophthora pluvialis, P. agathidicida, and Melampsora × columbiana. They have been listed in order of the most cited to the least cited species based on data obtained from the Web of Science. We provide a review for each species to document its emergence and its negative impact on the host(s). We also revise their taxonomic placement, host and country details, and provide updated phylogenetic trees for each genus. The number of accepted species based on molecular data is also