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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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 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

Tar Spot of Corn

Tar spot can cause severe yield loss on susceptible hybrids when conditions are favorable for disease. Tar spot appears as small, raised, black spots scattered across the upper and lower leaf surfaces. These spots are ascomatum (fungal fruiting structures). If viewed under the microscope, hundreds of sausage-shaped asci (spore cases)... Read More

Tobacco Ringspot of Soybean

Symptoms caused by Tobacco ringspot virus (TRSV) include bud blight, shepherd's crooking, stunting, wilting, delayed maturity, bud and leaf proliferation, reduced pod number, and discolored, distorted, and dead leaves. TRSV-infected plants may have discolored pith, petiole distortion and discoloration, leaf vein discoloration, and poor root nodulation. TRSV can be seed trans... Read More

Tobacco Streak of Soybean

Symptoms caused by Tobacco streak virus (TSV) include bud blight, shepherd's crooking, stunting, wilting, delayed maturity, bud and leaf proliferation, reduced pod number, and discolored, distorted, and dead leaves. TSV infection can cause discoloration and dead streaks at nodes, dark spots on pods, and delayed seed development. TSV can be seed transmitted but is also spread b... Read More

Trichoderma Ear Rot of Corn

Trichoderma ear rot of corn appears as dark green mold growing on or between kernels, often covering the entire ear. Kernels may sprout on the cob if disease is severe. It is primarily found on scattered plants under severe stress and is associated with injury to developing ears. Typically, it is not economically damaging. Grain sh... Read More

Wheat Streak Mosaic, High Plains Disease, and Triticum Mosaic of Wheat

Wheat streak mosaic, High plains disease, and Triticum mosaic are part of a virus disease complex found in most wheat growing regions of the U.S. and into Canada. These diseases are caused by Wheat streak mosaic virus (WSMV), High plains wheat mosaic virus (HPWMoV), and Triticum mosaic virus (TriMV), respectively. Co-infection... Read More

White Mold of Soybean

White mold (also called Sclerotinia stem rot) is a significant problem in the North Central soybean production region and Canada. White mold is often recognized by fluffy, white growth on soybean stems. Initial symptoms generally develop from R3 to R6 as gray to white lesions at the nodes. Lesions rapidly progress above and belo... Read More