Chrysanthemum white rust in diameter, but may turn brown as the tissue becomes necrotic. On the underside of the leaf, the spots develop into pink or white pustules that become prominent as the teliospores develop. Chrysanthemum white rust Chrysanthemum white rust is a disease of plants caused by the fungus Puccinia horiana that infects species of the genus "Chrysanthemum". Chrysanthemum white rust was first identified in Japan, although it is now established throughout Asia, Europe, South America. It has been found in the United States, Australia, and New Zealand on several occasions, but early detection and eradication efforts have prevented the disease from
Rust Rust Rust is an iron oxide, a usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Several forms of rust are distinguishable both visually and by spectroscopy, and form under different circumstances. Rust consists of hydrated iron(III) oxides FeO·"n"HO and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)). Given sufficient time, oxygen, and water, any iron mass will eventually convert entirely to rust and disintegrate. Surface rust is flaky and friable, and it provides no protection to the underlying iron, unlike the formation of patina on copper surfaces. Rusting is the common term