A Synoptic Review of Plant Disease Epidemics and Outbreaks Published in 2021

A synoptic review of plant disease epidemics and outbreaks was made using two complementary approaches. The first approach involved reviewing scientific literature published in 2021, in which quantitative data related to new plant disease epidemics or outbreaks had been obtained via surveys or similar methodologies. The second approach involved retrieving new pest presence records added to the CABI Distribution Database in 2021. The literature review for the first approach had two stages. Stage 1 aimed to identify publications on plant diseases caused by pathogen taxonomic groups and led to retrieval of 99 core articles describing studies in 62 categories (pathogen species or species complexes) across more than 40 host species in 6 continents. In Stage 2, the core articles were augmented with further articles providing more context and information for the pathogen species identified in Stage 1. When both sets of articles were combined, the pathogen species with more than 5 articles were: Bursephalenchus xylophilus, Candidatus Liberibacter asiaticus, cassava mosaic viruses, citrus tristeza virus, Erwinia amylovora, Fusarium spp. complexes, Fusarium oxysporum f.sp cubense, Magnaporthe oryzae, maize lethal necrosis co-infecting viruses, Meloidogyne spp. complexes, Pseudomonas syringae pvs, Puccinia striiformis f.sp tritici, Xylella fastidiosa, and Zymoseptoria tritici. The automated search of the CABI Distribution Database led to 617 new distribution records from 283 plant pathogens in 2021 and was followed by manual review of all pathogens with more than 4 new records, to identify confirmed first reports in a new location. A total of 15 pathogens was identified: apple hammerhead viroid, apple rubbery wood viruses, Aphelenchoides besseyi, Biscogniauxia mediterranea, Ca. Liberibacter asiaticus, citrus tristeza virus, Colletotrichum siamense, cucurbit chlorotic yellows virus, Erwinia rhapontici, Erysiphe corylacearum, Fusarium oxysporum f.sp. cubense Tropical Race 4, Globodera rostochiensis, Nothophoma quercina, potato spindle tuber viroid, and tomato brown rugose fruit virus. Although 3 very important pathogens – Ca. Liberibacter asiaticus, citrus tristeza virus and Fusarium oxysporum f.sp cubense – were represented in the results of both approaches, in general the two approaches revealed distinct sets of plant disease outbreaks and new records, with little overlap in the results.