Control of Alternaria Brown Spot (<em>Alternaria alternata</em> (Fr.) Keissler) in Citrus: A Systematic Review

Alternaria brown spot is one of the most critical diseases affecting susceptible mandarins worldwide, being a limiting factor for their cultivation. Although there are numerous reports on effective substances against the disease, field control is failing. In the literature, some of the results are contradictory, depending on the study and experimental scale. Therefore, this paper aimed to collate, analyze, and synthesize the most relevant empirical evidence to answer the following questions: (i) What substances have been used to control ABS and what is their effectiveness? (ii) What are the methodologies used to test the sub-stances? (iii) Why is ABS field control failing and what are the main factors hindering such control? An extensive literature search was performed in five databases: WoS, Scopus, Google Scholar, PubMed, and SciELO. The search string used was “Alternaria alternata” AND “Citrus”. Records were classified into ten groups according to their main topic. Group 3 “natural substances” and Group 4 “fungicides” were full text reviewed for data extraction (98 reports). Details of the natural substances and fungicides used against A. alternata, as well as summaries of the methodologies are provided. During this research, we highlighted significant aspects that may be hindering the control of Alternaria alternata in citrus: long periods of fruit sensitivity, abundance and floatability of inoculum, rapid infections, the appearance of resistance to fungicides, moderate effectiveness inhibiting the germination of conidia, uncertainty about the times of application, and persistence of the products.