Diseases

Use the Search and Filter options to help select only the crops, types of disease, and timing of disease you are interested in from the list below. Only articles meeting your chosen criteria will be shown. These articles contain information and images for identification and basic management of crop diseases.

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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

Charcoal Rot of Soybean

Initial symptoms of charcoal rot are patches of stunted or wilted plants. Leaves remain attached after plant death. The fungus produces numerous tiny, black fungal structures called microsclerotia that are scattered throughout the pith and on the surface of taproots and lower stems. These microsclerotia give the lower stem and... 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 Bunt of Wheat

Common bunt is also known as covered smut or stinking smut, and reduces yield and grain quality. Though historically important, current management practices typically prevent major losses. Evidence of common bunt is rarely present before ripening, but some stunting may occur. As heads ripen (FGS 10.5.3), spikelets may develop a... Read More

Common Root and Foot Rot of Wheat

Common root and foot rot occurs in all wheat production areas of the U.S. and Canada. The causal pathogen has a wide host range and also causes a foliar disease known as spot blotch. Symptoms include dark, chocolate brown to black lesions on the coleoptile, stem, roots, and/or subcrown internode (the area above the seed to the soil line). Heavily... 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

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

Downy Mildew of Soybean

Downy mildew of soybean is common but seldom causes serious yield loss. Lesions occur on upper leaf surfaces as irregularly shaped, pale green to light yellow spots that enlarge into pale to bright yellow spots. Older lesions turn brown with yellow-green margins. Young leaves are more susceptible, so disease is often found in the up... Read More

Dwarf Bunt of Wheat

Dwarf bunt is also known as dwarf smut. It typically occurs with long periods of snow cover, and only impacts winter wheat. Symptoms prior to heading (FGS 10.5) include yellow leaf flecking at late seedling stage, stunting, and excessive tillering. Once the head emerges, the fungus transforms kernels in... Read More

Ergot of Wheat

Ergot has played an important role in history as it impacts human and animal health. Though less problematic today, the disease can still cause issues, particularly in male-sterile wheat lines. During early infection, some kernels go through a "honeydew" stage where infected ovaries swell and emit a yellow, slime-like fluid. This fluid attracts insects and is full of spores. Ova... 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

Eyespot of Wheat

Eyespot, also called strawbreaker foot rot, can cause yield losses up to 50%. Winter wheat is affected more than spring wheat because environmental conditions are more conducive. Symptoms appear on stems directly above or below the soil surface. Stems develop a light tan to yellow-brown, eye-shaped l... Read More

Frogeye Leaf Spot of Soybean

Frogeye leaf spot of soybean occurs across the United States and in Ontario, Canada. Frogeye leaf spot can cause significant yield loss when widespread within a field. Leaf lesions are small, irregular to circular in shape, and gray with reddish-brown borders. Most commonly occurring on the upper leaf surface, lesions start a... 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 Head Blight of Wheat

Fusarium head blight (FHB) is currently the most economically important wheat disease in the U.S. and Canada. This disease is also known as scab or head blight. It reduces yield and produces mycotoxins that impact human and animal health. Infected spikelets are bleached and disease spreads upward and downwar... Read More

Fusarium Root, Crown, and Foot Rot of Wheat

Fusarium root, crown, and foot rot of wheat is widespread and can be found in all wheat production regions of the U.S. and Canada. Seedling blight occurs when Fusarium-infected seed is sown. Infected seedlings tend to be reddish with poor vigor and poor tiller production. Root, crown, and foot rot symptoms include da... Read More

Fusarium Root Rot and Wilt of Soybean

Fusarium is a very common soil fungus, and more than 10 different species are known to cause root rot. However, the economic impact on yield is not well documented. Infected seedlings exhibit poor or slow emergence and are often stunted. Root rot appears as reddish-brown to dark brown discolored roots and poor nodulation. Foliar symptoms of Fusarium wilt includ... Read More