Symptoms and Signs

Early infection appears as a light yellow flecking of the leaves. As these flecks enlarge, they may become somewhat longer than broad and when numerous they are arranged in rows parallel with the veins of the leaves. Soon, the epidermis ruptures and the spots develop into reddish-brown pustules. Severely infected plants have an appearance similar to rusty-iron, hence the name rust. When infected leaves are rubbed between your fingers or walked upon, a red powder collects on fingers or shoes. This powder is composed of millions of tiny spores of the fungus. Rust is normally a late summer or early fall problem and does not occur during other times of the year.

The Ascochyta fungus produces minute yellow to dark brown, flask-shaped fungal fruiting bodies called pycnidia in diseased leaf tissue. These fruiting bodies, which are easier to view with the aid of a hand lens, are peppered throughout the dead leaves and can be very useful as a diagnostic feature.

Management:

Adequate nitrogen and irrigation to maintain growth through late summer will minimize rust infections. In most years, the disease will not become severe, although infected turf may become yellowish-orange.

Fungicides are used only as a last resort; one or two sprays applied after the onset of symptoms usually will suffice.

Please check the "Extension Agents' Handbook of Insects, Plant Disease and Weed Control".