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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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

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