Encyclopedia - Soybeans

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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

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

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 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

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 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 Soybean

The root-knot nematode (RKN) causes damage on soybeans mostly in the Southern United States, however, can be found across the United States and in parts of Canada. Common foliar symptoms of RKN include stunting, reduced vigor, yellowing, wilting and death. Galls form on the roots of soybeans at the infection site which are caused by increased cells and cell number around the infection. 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

Southern Blight of Soybeans

Southern blight is caused by a soilborne fungus that has a wide host range of more than 200 plant species. Once considered a minor issue in soybean in the South, it has become more problematic, especially in fields with a history of the disease. 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 Gall Midge in Soybean

Soybean gall midge is a recently discovered soybean pest found in the Midwestern United States. It has continued to spread to new fields since its initial discovery in 2018. 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

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

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

Taproot Decline of Soybean

Taproot decline (TRD) of soybean was first detected in the mid-2000s in the southern U.S., and has been observed to result in yield losses approaching 25 percent. Symptoms generally occur at pod filling stages (R4-R6), but can be observed anytime during the growing season. Read More

Target Spot of Soybean

Target spot is caused by a fungus that can infect nearly all soybean plant parts. Prior to 2010 it was considered a minor disease of soybean; however, severe infections on susceptible varieties can cause significant defoliation across the southern U.S. The target spot pathogen can infect other row crops such as cotton. Read More