Alternaria è un genere di funghi che comprende specie che causano un tipo di muffa, particolarmente diffusa in Italia, che cresce su frutta e verdura in decomposizione e in ambienti particolarmente umidi (caratterizzati da una temperatura che varia tra i 18° e i 32° ed un tasso di umidità superiore al 65%) rilasciando le sue spore soprattutto su carta da parati, tappeti e terriccio.
È una delle principali cause di reazioni allergiche quali asma, congiuntivite, rinite e dermatiti.
L'insorgenza degli attacchi avviene principalmente tra metà luglio e settembre, periodo nel quale si ha la massima concentrazione di spore nell'aria, ma in generale il rischio sussiste a temperature superiori ai 18°C.
Specie
Il genere Alternaria comprende specie saprofite e specie parassite; queste ultime causano svariate patologie soprattutto su piante erbacee. Dal punto di vista fitopatologico le specie più importanti di questo fungo sono:
Le spore di Alternaria sono di ridottissime dimensioni[nonchiaro] e, similarmente ai pollini, vengono inalate facilmente provocando allergia in soggetti intolleranti.
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