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Alternaria brown spot (ABS), caused by Alternaria alternata, is one of the main citrus diseases that causes heavy production losses and reductions in fruit quality worldwide. The application of chemical fungicides has a key role in the management of ABS. In this study, 48 isolates of A. alternata collected from citrus orchards since 2014 were tested in vitro for their sensitivity to pyraclostrobin and fludioxonil, the latter being temporarily registered in Italy since 2020. Pyraclostrobin sensitivity was determined using spore germination and mycelial growth assays. The effective concentration inhibiting 50% of fungal growth (EC50) was determined for each isolate. The sensitivity assays showed that the majority of A. alternata isolates tested were sensitive to pyraclostrobin. EC50 values of fludioxonil in a mycelial growth assay indicated that 100% of isolates were sensitive to this fungicide. The analysis of the cytochrome b gene showed that none of the 40 isolates with a different sensitivity profile had the G143A mutation, and the subgroup of 8 isolates analyzed by real-time PCR did not carry the G137R and F129L mutations. A subset of four more sensitive and two reduced-sensitive isolates was chosen to assess sensitivity on detached citrus leaves treated with pyraclostrobin at the maximum recommended label rate. Disease incidence and symptom severity were significantly reduced, with a small reduction reported in leaves inoculated with the reduced-sensitive isolates. Furthermore, there was no correlation between sensitivity and fitness parameters evaluated in vitro (mycelium growth and sporulation rate). These findings help the development of monitoring resistance programs and, consequently, set up effective anti-resistance strategies for managing ABS on citrus orchards. [ABSTRACT FROM AUTHOR]

Pestalotioid fungi were isolated in pure culture from symptomatic plants of Callistemon laevis, C. viminalis, Luma apiculata (marketed as "Myrtus luma"), Myrtus communis subsp. tarentina, and M. communis var. microphylla (M. communis 'Microphylla'), showing twig canker, dieback and defoliation. The isolates were identified to species by ITS, tef1 and tub2 sequences, which revealed the presence of six species of Neopestalotiopsis (N. camelliae-oleiferae, N. hispanica, N. iberica, N. rosae, N. rosicola, and N. zakeelii) and one species of Pestalotiopsis (P. biciliata). While most species were isolated only once or twice, the majority of isolates belonged to N. rosae (13) and N. hispanica (8). Pathogenicity was investigated by pathogenicity tests on all hosts, which confirmed the pathogenicity of all Neopestalotiopsis species on at least some of the hosts tested, while P. biciliata did not cause any disease symptoms. Neopestalotiopsis hispanica and N. rosae caused symptoms in all hosts of the present study, while the other Neopestalotiopsis species tested showed no symptoms on Luma apiculata. [ABSTRACT FROM AUTHOR]

Many fungi belonging to Botryosphaeriaceae are well-known as causal agents of diseases in economically and ecologically important agricultural crops and forest trees. In Italy, the high diffusion of Botryosphaeriaceae infections observed over the last decade, has shown the importance of this group of fungi, which are becoming limiting factors for plant production in agricultural systems, nurseries and natural and urban landscapes. Global warming and stress factors such as occasional extreme climatic events can affect the susceptibility of host plants, as well as fungus behaviour, increasing the risk of future infections. Available reports of Botryosphaeriaceae in Italy have been examined, focusing on wood and fruit pathogens, resulting in a list of ten genera and 57 species. Diplodia is the most widespread genus in Italy with 76 records on 44 hosts, while at species level, Neofusicoccum parvum, Botryosphaeria dothidea and Diplodia seriata show the widest host ranges and many records. The ability of the pathogens to remain latent on asymptomatic plants, and uncontrolled trade of plant materials among countries, facilitate the dissemination and potential introduction of new Botryosphaeriaceae species. Preventive detection and adequate control strategies are always needed to limit the potential damage caused by Botryosphaeriaceae. This review had particular emphasis on host-pathogen associations, disease symptoms, geographic distribution, metabolite production, and accurate pathogen identification. [ABSTRACT FROM AUTHOR]