Encyclopedia - Corn

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Anthracnose Leaf Blight of Corn

Anthracnose leaf blight seldom causes yield loss. Early in the season, lower leaves usually show symptoms first. Later, symptoms can occasionally be found on upper leaves. Leaf lesions are oval or spindle shaped, tan or brown with dark brown or purple margins, up to 1 inch long and ½ inch wide. As... Read More

Anthracnose Stalk Rot of Corn

Anthracnose is likely the most prevalent stalk rot in the eastern United States. Affected plants have shredded pith and die prematurely. Anthracnose also causes a distinctive blackening of the stalk rind. Initially, these areas are narrow, water-soaked lesions, but they turn very dark and shiny and can join together to form large black blotches or streaks over the gro... Read More

Aspergillus Ear Rot of Corn

Aspergillus ear rot is one of the most important diseases of corn. Typically, this disease is more common in the southern United States than in other areas. Aspergillus ear rot appears as an olive-green mold on the kernels that may begin at the tip of the ear or... Read More

Bacterial Leaf Streak of Corn

Bacterial leaf streak has been observed on field corn, seed corn, popcorn, and sweet corn. Symptoms are tan, brown, or orange lesions that occur between the veins of the corn leaves. Lesions are long, narrow, and less than 1 inch to several inches long. Lesions also can occur close to the leaf midrib or acro... Read More

Bacterial Stalk Rot of Corn

Bacterial stalk rot can occur any time during the season, particularly if conditions are very wet. It causes decay of the first internode above the soil. The rind and the pith become soft, brown, and water-soaked. Affected plants have a foul odor. The stalk typically twists and falls over, but the plant may remain green for several we... Read More

Charcoal Rot of Corn

Charcoal rot causes the pith and rind of affected plants to appear gray because of the numerous tiny black microsclerotia that develop. The pith tissue is disintegrated, leaving the vascular tissue with a granular, gray appearance. The fungus overwinters as sclerotia in crop residue and soil and infects plants through roots. It may occur... Read More

Cladosporium Ear Rot of Corn

Cladosporium ear rot appears as dark green or black powdery mold and black streaks on kernels. It usually forms first where the kernels attach to the cob. Dark green, fuzzy mold also may be observed on and between kernels. This ear rot is often associated with hail, frost, or insect injury and is favored by wet weather... Read More

Common Rust of Corn

Common rust of corn occurs every growing season. It is seldom a concern in hybrid corn. Rust pustules usually first appear in late June. Early symptoms of common rust are chlorotic flecks on the leaf surface. These soon develop into powdery, brick-red pustules as the spores break through the leaf surface. Pustules are oval or elongated, about... Read More

Common Smut of Corn

Common smut galls can form on stalks, leaves, ears, and tassels; actively growing tissue is especially susceptible. Galls are swollen, distorted growths that are at first covered with a glistening white membrane. The membrane eventually ruptures to reveal a mass of dark brown or black powdery spores. Common smut galls on co... Read More

Crazy Top of Corn

Crazy top-affected plants are distorted and/or stunted. The leaves below the tassel may proliferate, resulting in a very bushy appearance of the top of the plant, which lends this disease its name. Internodes may be short or long; there may be a proliferation of ear shoots, leaves that are narrow... Read More

Curvularia Leaf Spot of Corn

Curvularia leaf spot is a fungal disease that was officially reported in the U.S. for the first time in 2017. This foliar disease has been observed in multiple states. Symptoms include small, tan-colored lesions with brown margins that may be surrounded by a yellowish halo. Read More

Diplodia Ear Rot of Corn

Diplodia ear rot has become a common (and troublesome) disease on corn. The causal fungi produce mycotoxins in South America and Africa, but no mycotoxins have been associated with Diplodia ear rot in the United States and Canada. This ear rot is recognized as a white mold beginning at the base of the ear that... Read More

Diplodia Stalk Rot of Corn

Plants affected by Diplodia stalk rot have shredded pith and die prematurely. Numerous black dots, about the size of a pinhead or smaller, can be observed in the lower internodes of the stalk. Under very wet conditions, a white mold may develop on the stalk surface. Infections occur through the crown, roots... Read More

Eyespot of Corn

The initial symptoms of eyespot are small, water-soaked or chlorotic circular spots. The tissue at the center of the spot later dies and turns tan-colored with a brown ring at the margin. The spot is surrounded by a yellow "halo" that can be seen clearly when the leaf is lighted from behind. Spots may join together into large... Read More

Fusarium Ear Rot of Corn

Fusarium ear rot is the most common ear disease. Symptoms are a white to pink or salmon-colored, cottony mold that occurs on single or multiple kernels scattered or clustered on the ear. Decay often begins with insect-damaged kernels. Infected kernels are frequently tan or brown or have white streaks. Causal fungi overwinter... Read More

Fusarium Stalk Rot of Corn

Fusarium stalk rot of corn is among the most common stalk rots in the Midwest. Affected plants have shredded pith that may be a whitish-pink to salmon color and die prematurely. Brown streaks may be observed on the lower internodes. Pith shredding indicative of... Read More

Gibberella Crown Rot and Stalk Rot of Corn

Gibberella stalk rot affected plants have shredded pith that is discolored a distinct pink or red and will die prematurely. Gibberella stalk rot causes dark streaks on the lower internodes. In moist conditions, round black specks may form at the lower nodes. These specks can be scratched off the stalk surface easily using a fing... Read More

Gibberella Ear Rot of Corn

Gibberella ear rot of corn is a consistently important mycotoxigenic fungus in the northern Corn Belt, producing vomitoxin, zearalenone, and other toxins. Gibberella ear rot can be identified most readily by the red or pink color of the mold. It almost always begins at the tip of the ear. Excessive mold may cause silks and husks to adh... Read More

Goss's Wilt of Corn

Goss's wilt of corn is caused by a bacteria which can infect leaves at any stage of plant growth. Leaf lesions are long, gray-green to black, water-soaked, and have wavy edges. Streaks resembling freckles within the lesions are a distinctive symptom of this disease. Droplets of bacterial exudate eventually ooze from these freckles. As... Read More

Gray Leaf Spot of Corn

Gray leaf spot of corn occurs virtually every growing season. If conditions favor disease development, economic losses can occur. Symptoms first appear on lower leaves about two to three weeks before tasseling. The leaf lesions are long (up to 2 inches), narrow, rectangular, and light tan colored. Later, the lesions can turn gray. They a... Read More