Rust Spots on Leaves
The emergence of spots is always connected with a pest attack or the consequences of launched disease processes. Also, the brown color of such spots points to rust caused by a group of fungi from the Pucciniales family. The unusually-looking spots and growths of unnatural orange, yellow, and brown shades located on leaves signalize the disease. For the development of these pathogens, high humidity that causes long-term wetting of the leaves is a must. Fungal rust is the most common cause of leaf spots, although there are others as well. Alternatively, rusty spots indicate a lack or excess of phosphorus, nitrogen, boron, copper, iron, magnesium, potassium, etc.