MAL SECCO DISEASE OF CITRUS: A JOURNEY THROUGH A CENTURY OF RESEARCH
F. Nigro, A. Ippolito, M.G. Salerno
“Mal secco”, an Italian name meaning “dry disease”, is a severe tracheomycotic disease of citrus caused by the mitosporic fungus Phoma tracheiphila (Petri) Kantsch. et Gik. It appeared in 1894 in two Aegean Greek islands, from which it spread almost to the whole Mediterranean basin and the Black Sea. Due to its high susceptibility, lemon is the most damaged citrus species. Disease damage consists of substantial reduction of the quality and quantity of the crop, mainly due to the difficulties of controlling the disease and the replacement of susceptible valuable cultivars by others which are less vulnerable, but have low productivity and scarce fruit quality. Control of mal secco disease has relied on a number of diverse chemical and nonchemical strategies, but is still faced with efficacy problems. Host resistance remains a most desirable goal, but it will not be ultimately achieved until the genetic basis of resistance to P. tracheiphila are not fully elucidated. The present paper reviews the different aspects of citrus mal secco as studied worldwide over almost a century of research, from the first appeareance of the disease in Italy (1918) to date. Milestones and pitfalls about the symptomatology, aetiology, host-parasite relationship, diagnosis, epidemiology, and control are discussed in a historical perspective, emphasizing the advancements in knowledge. Finally, some issues and challenges are highlighted that need to be more comprehensively addressed prior to deployment of effective disease control measures.