Encyclopedia

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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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

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

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

Thielaviopsis Root Rot of Soybean

Thielaviopsis root rot, also called black root rot, is caused by a fungus that infects the root system early in the season. The fungus causes black discoloration of the taproot and rotting of the hypocotyl. Plants may have symptoms of stunting, shortened internodes and yellow spots along the leaf veins and in severe situations plants may die. 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

Wildfire of Soybeans

Wildfire of soybeans is an uncommon bacterial disease that is mainly found in the southern United States. Symptoms include lesions that are light to dark brown which normally have yellow halos. Read More