This hub is designed as a quick guide for identifying maize diseases caused by fungi. It is intended for field use by agricultural technicians and producers. The text comprises a brief description of some of the principal maize diseases, their causal agents, and their symptoms. This text will give you quick information about the Maize Diseases Caused by Fungi

Brown Spot (physoderma maydis)

Normally the maize disease occurs in areas of abundant rainfall and high mean temperatures. It attacks the leaves, leaf sheaths, stalk, and sometimes the outer husks.

The first noticeable symptoms develop on leaf blades and consist of small chlorotic spits, arranged as alternate bands of diseased and healthy tissue. Spots on the mid-ribs are circular and dark brown, while lesions on the laminae continue as chlorotic spits. Nodes and internodes also show brown lesions. In severe infections, these may coalesce, and induce stalk rotting and lodging. So, maize fungi disease can be found as Brown spot.

Downy Mildews

Several species of the genera Sclerospora and Sclerophthora are responsible for downy mildews: Crazy Top, Yellow Wilt of Rice (sclerophthora macrospora), Brown DtripeDowny Mildew (sclerophthora rayssiae var. zea), Graminicola Downy mildew of Maize Green Ear Disease(sclerospora graminicola), Java Downy Mildew of Maize (Peronosclerospora maydis), Philippine Downy Mildew of Maize (Peronosclerospora philippinensis), Sugarcane Downy Mildew of Maize (Peronosclerospora sacchari), Sorghum Downy Mildew of maize (Peronosclerospora sorghi)

These diseases are of serious concern to maize producers in several countries of Asia and Africa. Recent information indicates that their distribution is increasing throughout the American continent. Symptom expression is greatly affected by plant age, species of the pathogen, and environment. Usually, there is chlorotic striping of leaves and leaf sheaths, and dwarfing. Downy mildew becomes conspicuous after development of a “downy growth” on or under leaf surface. This condition is the result of conidia formation, which commonly occurs in early morning.

The disease is most prevalent in warm and humid regions. Some species causing downy mildew also induce tassel malformations. Consequently, no pollen is produced, and ears, narrow, thick, and abnormally erect.

Tar Spot (Phyllachora Maydis)

The disease sometimes occurs in relatively cool, humid areas of the tropics, where Turcicum leaf blight is prevalent. Characteristic black, raised and shiny spots are produced early. At a later stage, necrotic areas develop around the Tar Spot. These necrotic lesions may coalesce and cause a complete burning of the foliage. Lesions start developing before tasseling time on lower leaves. If environment is favorable, infection continues upwards on younger leaves. Affected ears are light weight with loose kernels.

Maize Rusts

There are three major leaf rust on maize are common rust, Polysora rust, and tropical rust.

Common rust (puccinia sorghi)

Common rust is most con specious when plants approach tasseling. It may be recognized by small, powdery pustules over both surfaces of the leaves. Pustules are brown in early stages of infection; later, the epidermis is ruptured and the lesions turn black as the plants matures. Plants of the alternate host (oxalis spp.) are frequently infected with light orange colored pustules. This is simply another stage of the same fungus.

Polysora rust (Puccinaia Polysora)

Pustules are smaller, lighter in color, and more circular than those produced by P. sorghi. They are also present on both leaf surfaces, but the epidermis remains intact longer than it does in P. sorghi-infected leaves. Pustules turn dark brown as plants approach maturity. No alternate host of the fungus is known. Southern rust, as polysora rust is often called, is common in hot and humid regions.

Tropical Rust (Physopella Zeae)

Pustules vary in shape from round to oval. They are small and found beneath the epidermis. At the center of the pustule the lesion appears white to pale yellow and an opening develops. The pustule is sometimes black rimmed, but its center remains light. No alternate host of the fungus is known.