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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Powdery Mildew of Soybean

Powdery mildew of soybean is the most common and characteristic sign of powdery mildew is white, powdery fungal growth that can cover all aboveground plant parts, particularly the upper leaf surface. Later symptoms may include plant tissue yellowing and premature defoliation. Powdery mildew usually does not appear until mid- to late reproductiv... Read More

Powdery Mildew of Wheat

Powdery mildew is a common disease of wheat throughout the U.S. and Canada wherever winter wheat is grown. It is an economic problem primarily in the eastern soft winter wheat region. The characteristic sign of the powdery mildew pathogen is fluffy, white to gray fungal growth on the top surface of leaves. Yellowish spots b... Read More

Purple Seed Stain of Soybean

Soybean seeds with purple seed stain can be symptomless or have pink to purple spots extending from the hilum. Discoloration can cover the entire seed or appear as small spots. Crop value may be lowered by dockage or seed certification denial, but yield is not reduced. Purple seed stain incidence can be increa... Read More

Pythium Root Rot of Wheat

Pythium root rot is a soil-borne disease that reduces yield in wheat growing regions throughout the U.S. and Canada. Symptoms include stunting, yellowing, tiller reduction, and poor stand. Symptoms are generally more noticeable in low lying areas. Infected roots are shorter, have few root hairs, and are necrotic. The... Read More

Pythium Seedling Blight and Root Rot of Soybean

Pythium species cause pre- or postemergence damping off. Infected seeds appear rotted and soil sticks to them. Infected seedlings have water-soaked lesions on the hypocotyl or cotyledons that develop into a brown soft rot. Diseased plants are easily pulled from the soil because of rotted roots. Rotted seedling root from Pythium infection. Read More

Pythium Stalk Rot of Corn

Pythium stalk rot of corn 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. The stalk typically twists and falls over, but the plant may remain green for several weeks because the vascu... Read More

Red Crown Rot of Soybean

Red crown rot causes deterioration of soybean roots and stems. Fields affected with RCR typically show symptoms after R3. At the field level, patches of symptomatic plants often occur in low lying or poorly drained areas of the field.  Read More

Rhizoctonia Root Rot of Wheat

Rhizoctonia root rot of wheat occurs in temperate regions and is also called bare patch. Field symptoms include bare patches or areas of uneven plant height. Severe infection causes plants to be stunted, appear drought stressed or nutrient deprived, and may result in premature plant death. Mild infection may go unnoticed abov... Read More

Rhizoctonia Seedling Blight and Root Rot of Soybean

Rhizoctonia seedling blight and root rot of soybean can cause pre- and postemergence damping off. Infected seedlings have reddish-brown lesions on the hypocotyls at the soil line. These lesions are sunken and remain firm and dry. The root rot phase may persist into late vegetative to early reproductive growth stag... Read More

Root-Knot Nematode of Wheat

Root-knot nematodes are one of the most destructive plant-parasitic nematodes. The root-knot nematode commonly produces small, curved or horseshoe shaped-galls near root tips. Typically, galls are larger and easier to recognize toward the end of the growing season. Severely infected plants are often st... Read More

Root-Lesion Nematode of Wheat

Root-lesion nematode is found in most wheat production areas in the U.S. and Canada. It has a wide host range and can be very destructive in wheat. Symptoms include chlorosis of lower leaves, stunting, fewer tillers, and delayed plant growth. The root mass is reduced as nematodes degrade roots and reduce branching. Roots tend to turn brown, and oth... Read More

Root Rots of Corn

Corn root rots are very common and are caused by several soilborne pathogens. Root rots occur to some extent in every field, causing economic losses under wet conditions. Aboveground symptoms include stunting, uneven growth, chlorosis, small or poorly filled ears, or wilting. In saturated conditions, effects of root rot are difficult... Read More

Seed Decay and Seedling Blight of Corn

Many pathogens cause seed decay and seedling blight of corn. The first symptom may be an area of the field with poor or no stand. Decayed seeds are very soft and may be covered with fuzzy fungal growth; seeds can be difficult to find if badly rotted. Postemergence damping off appears as yellowing a... Read More

Septoria Brown Spot of Soybean

Septoria brown spot is the most common foliar disease of soybean. Disease develops soon after planting and is usually present throughout the growing season. Symptoms are typically mild during vegetative growth stages of the crop and progress upward from lower leaves during grain fill. Infected young plants have purple les... Read More

Septoria tritici Blotch of Wheat

Septoria tritici blotch is a common disease of wheat, often occurring alongside other foliar diseases. It is also known as Septoria leaf spot. Elliptical, tan-brown lesions that often have yellowish halos first appear on seedling leaves. Lesion centers die and dark fruiting bodies are produced, giving the lesion a characteristi... Read More

Sharp Eyespot of Wheat

Sharp eyespot, also called spring blight, infects wheat in temperate regions of the U.S. Tan, lens-shaped lesions with dark borders initially appear on the outer leaf sheath of lower stems, often between the crown and third node. Mature lesions eventually turn dark brown. Lesions result in formation of a hole in leaf sheaths. White fu... Read More

Snow Molds of Wheat

Snow molds occur primarily where snowfall accumulates and are caused by several pathogens. Symptoms are typically patchy and appear after snow melts in spring. Severe infection can damage the growing point, causing plant death. With pink snow mold, infected po... Read More

Southern Corn Leaf Blight of Corn

The pathogen that causes southern corn leaf blight has two races. Race O normally attacks only leaves. Lesions are tan, somewhat rectangular in shape, and have reddish-brown margins. Race T attacks leaves, husks, stalks, leaf sheaths, shanks, ears, and cobs. Race T lesions are rectangular to elliptical (¼ to ½ inch wide by... Read More

Southern Rust of Corn

Although southern rust is generally considered a tropical disease, it can occur in important corn production areas of the United States and Canada. Symptoms are similar to common rust, but pustules are smaller and occur almost exclusively on the upper leaf surface. Pustules are usually circular or oval, very numerous, a... Read More

Soybean Cyst Nematode of Soybean

Damage from the soybean cyst nematode (SCN) may not be obvious in high-yielding fields or during years when soil moisture is plentiful. However, yield losses of 40 percent or more are still possible. When symptoms are associated with damage, symptomatic plants usually occur in patches. Noticeable symptoms of SCN include stunting, slow or no can... Read More