Alternaria sp. is a genus of fungi that includes several phytopathogenic species that affect a wide range of plants, including chard. These fungi are saprophytic and necrotrophic, capable of surviving on plant remains in the soil or on infected seeds during unfavorable periods. Alternaria produces conidia in long chains that are easily dispersed by wind, water, and physical contact. These conidia germinate in conditions of high humidity, penetrating the plant tissue through wounds or directly through the stomata. Once inside the plant, the fungus produces toxins that kill cells and feed on dead material, forming characteristic necrotic Taches. Alternaria development is favored by warm, humid environments, allowing for multiple cycles of infection during a growing season.