Why Corn Stalks Turn Brown

Stalk Rot Description

• Stalk rots are a rampant disease of corn plants caused by fungal and bacterial infections. Those causing visible brown discoloration include fungal pathogens that attack older plants reaching maturity, according to the University of Illinois Extension. Annual crops may experience significant losses from stalk rot; corn crops in states like Illinois have experienced up to a 20 percent loss. Corn plants may die early or collapse while developing because of infection.

Gibberella and Fusarium Stalk Rot

• Stalk rot caused by the fungi "Gibberella" and "Fusarium" results in brown stalks. Stalk plant tissue first becomes pinkish red with Gibberella infections and white/pink to a salmon hue with Fusarium infections. Corn plant roots, crown and internodes are also affected; these plant parts experience rot. Small black mushroom-like growths sometimes appear with Gibberella infection. Symptoms often appear weeks after pollination, resulting in leaves and stalks that fade and turn brown. Plant tissue breaks down and in more vulnerable plants, the entire plant dies, according to the University of Illinois Extension.

Anthracnose Stalk Rot

• Anthracnose stalk rot, also referred to as top-dieback, is a fungal infection caused by the fungus Colletotrichum graminicola. This infection infects nearly all parts of the plant, including shanks, stalks, kernels and roots. A secondary problem is the formation of leaf blight, a subsequent fungal infection on leaves. With anthracnose, a dark brown to black glossy color appears on the rind and ascends the stalk, resulting in solid to spotted brown or black, according to the University of Illinois Extension. Often, the pith turns to a watery substance and leaf drop occurs.

Physoderma Stalk Rot

• Physoderma stalk rot is a fungal infection of corn that displays small, sometimes banded lesions, at the bottom of leaf blades. The small yellow lesions change to different shades of brown, including chocolate and red-brown; the spots combine, causing abnormal, geometrically shaped discolored areas. Additionally, areas of the stalk display lesions that appear saturated with water. Physoderma stalk rot results in decay of the corn plant, according to the University of Illinois Extension.

Control

• Stalk rot is not an easily controlled problem. Much of the management process includes preventive care, including planting resistant hybrid corn plants, controlling other problems like pest infestations, planting the correct amount of corn per determined area, waiting to harvest until the corn crop is fully mature and maintaining appropriately fertile soil preferred by corn plants; balanced levels of potassium and nitrogen may affect plant health. Determine the proper levels according to your particular corn variety. Though fungicides are not recommended for stalk rot, contact your local extension agent in the case of extremely severe infections.