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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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

Soybean Dwarf of Soybean

Symptoms caused by Soybean dwarf virus (SbDV) can vary due to virus strain, infection timing, and variety of soybean. Leaves can be dark green, brittle, wrinkled, curled, small, and thick while green stem, delayed maturity, plant stunting, yellowing between leaf veins, and decreased seed number can also occur. SbDV is transmitted by aphids and has multiple legume and non-l... Read More

Soybean Mosaic of Soybean

Foliar symptoms caused by Soybean mosaic virus (SMV) include distorted and wrinkled leaves that have a mottled color pattern. Symptoms appear more severe on young leaves, sometimes with a raised, blistered, or distorted appearance. Symptoms are most obvious at cooler temperatures and often disappear when it is hot. The major concern with soybean mosaic is reduced seed qua... Read More

Soybean Rust of Soybean

Soybean rust symptoms are most common after flowering, beginning on lower leaves. Lesions start to form on lower leaf surfaces as small, gray spots that change to tan or reddish-brown. Lesions are scattered within yellow areas appearing translucent if held up to the sun. Mature lesions contain one to many small pustules, usuall... Read More

Soybean Seed Quality Considerations for 2019

Seed quality from the 2018 soybean harvest was below average across the majority of the soybean-producing areas of the United States. Several factors led to poor-quality soybean seed, but some of the most important were wet conditions throughout the fall and subsequent delayed harvest. The wet conditions delayed harvest and created the right conditions for several seed diseases. Read More

Soybean Vein Necrosis of Soybean

Symptoms caused by Soybean vein necrosis virus (SVNV) often begin as yellowing near leaf veins that develops into reddish-brown lesions, causing death of leaf tissue. Lesions follow or spread from leaf veins. Leaf veins may limit lesions, resulting in an angular lesion appearance. Clear, yellow, or dark brown discoloration of leaf veins can occur. Browning of veins... Read More

Stagonospora Leaf and Glume Blotch of Wheat

Stagonospora leaf and glume blotch is very common in the U.S. and Canada and is often found with Septoria leaf spot. The leaf blotch phase of this disease can lead to a head infection phase, called glume blotch. Seed may also be infected. When infected seed is planted,... Read More

Stem Canker of Soybean

The first symptoms of stem canker are often dead plants with dried leaves that remain attached to petioles late in the season. Diseased plants usually occur in patches within fields. Stem lesions start as small, reddish-brown spots at the base of a branch or leaf petiole and then expand to form slightly sunken cankers... Read More

Stem Rust of Wheat

Stem rust of wheat, also known as black rust, is a problematic disease worldwide. A federal program and breeding efforts have kept the disease in check in the U.S. However, new variants of the stem rust pathogen virulent on many resistance genes currently used in the U.S. has been observed in Af... Read More

Stewart's Disease of Corn

Stewart's disease lesions spread from flea beetle feeding scars (a tiny scratch on the leaf) and are initially pale green to yellow streaks, later becoming brown as tissue dies. The margins of the streaks are usually wavy but generally follow leaf veins. If... Read More

Stripe Rust of Wheat

Stripe rust can occur anywhere in the U.S. and Canada, causing substantial yield losses when conditions are favorable. It is also known as yellow rust. Initially, symptoms are yellowish flecks on leaves. On susceptible varieties, pustules containing yellow-orange spores erupt from leaves. Pustules are clustered on seedling leaves, while pu... Read More

Sudden Death Syndrome of Soybean

Foliar symptoms of sudden death syndrome are a result of a toxin, produced by the fungus, moving from roots to the leaves. Foliar symptoms rarely appear until after flowering. Leaves of infected plants initially show scattered yellow spots between leaf veins. Spots grow to form large chlorotic and necrotic bl... Read More

Take-All of Wheat

Take-all of wheat occurs in temperate climates and can have a devastating effect. Plants with take-all initially have mild chlorosis, are stunted, and have poor tiller development. Around heading (FGS 10.5), patches of uneven, prematurely ripened wheat with white heads appear. Infected plants may eventually lodge. Roots are blac... Read More

Tan Spot of Wheat

Tan spot is an economically important disease occurring anywhere wheat is grown in the U.S. and Canada. It is also called yellow leaf spot. In susceptible wheat varieties, tan spot initially appears as small, brown spots on leaves. Spots enlarge and develop tan necrotic spots with a yellow halo. A pinhead size black spot may be... Read More