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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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 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

Gibberella 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

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

Head Smut of Corn

Head smut of corn forms on the tassels and ears, galls are at first covered with a thin layer of tissue that breaks open to expose the black spore masses and threadlike remains of the vascular bundles. Leaf-like proliferations develop on the tassel and ears. Ears may be aborted and replaced with a proliferation of leafy tissue. Plants als... Read More

Holcus Leaf Spot of Corn

Holcus leaf spot usually does not cause major losses. Leaf spots are initially oval to irregular, dark green, water-soaked at the margins, and may have a light brown border. Later, lesions dry out and turn light tan, usually without a border. The dry lesions have a papery texture. Holcus leaf spo... Read More

Leaf Rust of Wheat

Leaf rust, also called brown rust, occurs across the U.S. and Canada and can cause severe yield loss in epidemic years. Leaf rust pustules rupture the leaf epidermis, but lack conspicuous tear marks. These pustules contain orange-brown, rusty colored spores. Later in the season, dark brown to black spores are produced whic... Read More

Loose Smut of Wheat

Loose smut has a wide distribution and can occur anywhere wheat is produced. Mild symptoms may be present prior to heading, including yellowish leaf streaks and stiff, dark green leaves. Affected plants head out early, producing sterile heads with clumped, sooty olive-black spores in place of healthy glumes and kernels. Spores are... Read More

Maize Dwarf Mosaic of Corn

Maize dwarf mosaic is caused by the Maize dwarf mosaic virus. Infected plants have a stippled (small, discolored specks) mottle or mosaic of light and dark green that may develop into narrow streaks on the youngest leaves. There may be a shortening of internodes causing a stunted, bunchy appearance of the plant. As plants mature and temperatures rise, mosaic symptoms oft... Read More

Nematodes that Feed on Corn

Multiple plant-parasitic nematodes feed on corn roots. Although prevalent, they rarely cause economic damage. Symptoms of nematode damage can occur any time during the season and include poor or uneven stands, chlorosis, stunting, and small or poorly filled ears. Often, symptoms occur... Read More

Northern Corn Leaf Blight of Corn

Northern corn leaf blight (NCLB) symptoms usually appear first on the lower leaves. Leaf lesions are long (1 to 6 inches) and elliptical, gray-green at first but then turn pale gray or tan. Under moist conditions, dark gray spores are produced, usually on the lower leaf surface, which give lesions a "dirty" gray ap... Read More

Northern Corn Leaf Spot of Corn

Northern corn leaf spot, also known as Carbonum leaf spot, is occasionally seen in the lower canopy during periods of high humidity and moderate temperatures. There are five known races of this fungus. Races 2 and 3 are the most common in the Midwest. Race 2 causes oblong, somewhat rectangular, brown spots (¼ to ½ by 1... Read More

Penicillium Ear Rot of Corn

Penicillium ear rot of corn is characterized by green or blue-green powdery mold growing between kernels, usually at the tip of the ear. Infected kernels can appear bleached or streaked. This rot occurs primarily on ears damaged mechanically or by insects, and it is more common in non-Bt corn because of the greater potential for insect... Read More

Phomopsis Seed Decay of Soybean

Phomopsis seed decay of soybean can greatly affect seed quality. Phomopsis-infected seed are cracked and shriveled and are often covered with chalky, white mold. If infected seeds are planted, emergence may be low due to seed rot or seedling blight. Infected seedlings have reddish-brown, pinpoint lesions on the cotyledons or r... Read More

Phyllosticta Leaf Spot of Soybean

Phyllosticta leaf spot lesions most often occur on leaves and are circular, oval, and irregular or V-shaped. Lesions appear gray or tan and have a narrow, dark margin. In older lesions, numerous small, black specks (i.e., pycnidia) may be visible. The fungus likely survives in infested crop residue and can be seed tra... Read More

Physoderma Brown Spot of Corn

Symptoms of Physoderma brown spot usually appear on mid-canopy leaves. Leaf lesions are numerous, very small (approximately ¼ inch in diameter), round to oval, yellowish to brown in color, and usually occur in broad bands across the leaf. Alternating bands of infected and noninfected tissues are common.... Read More

Physoderma Stalk Rot of Corn

Physoderma stalk rot is caused by the same fungal pathogen that causes Physoderma brown spot. It is not usually an economic problem. Stalk rot symptoms are first noticed when plants break at the first or second node. These nodes are black and some pith rot may be present. Infected nodes snap easily if gently pushed. Microscopic examination of symptom... Read More

Phytophthora Root and Stem Rot of Soybean

Phytophthora root and stem rot of soybean can occur at any growth stage from seed to maturity. Early season symptoms include seed rot and pre- and postemergence damping off. The most characteristic symptom of Phytophthora root rot is a dark brown lesion on the lower stem that extends up from the taproot of the plant. The lesion often reaches as high as several nodes and... Read More

Pod and Stem Blight of Soybean

Pod and stem blight is characterized by black, raised specks that appear in linear rows on mature soybean stems. These specks are fungal reproductive structures known as pycnidia. Pycnidia can also cover pods, but they may not follow the linear pattern seen on stems. These signs are most prevalent from R6... Read More