Key Diseases in Corn, Soybeans, Cereals and Cotton

Soybean infected with frogeye leaf spot. Without proper management, crop disease can erode yields and profits.
Soybean infected with frogeye leaf spot. Without proper management, crop disease can erode yields and profits.

Without proper management, diseases in field crops can significantly rob yields and profits.

University of Iowa Extension field crops plant pathologist Alison Robertson notes that some diseases can steal 20 to 50 percent of a grower’s corn or soybean yield. “Farmers may see at least a five percent or more yield increase (in corn) from a fungicide application investment when diseases such as northern leaf blight or gray leaf spot are present and widespread in a field,” say says.

While some pathogens, such as Rhizoctonia or Fusarium, may affect more than one crop, most diseases, such as anthracnose, rusts, mildews, wilts and leaf spots are more crop specific or apply primarily to either grass or broadleaf crops.

How can growers address common crop diseases?

Among the many crop protection decisions growers make each season, disease management is an important part of the puzzle. In addition to best management practices for corn, soybeans, wheat and cotton – such as crop rotations – several products can help manage disease resistance and greatly increase success.

For more information on crop specific diseases, click on the appropriate crop image below.

Key Diseases in Corn

  • Gray Leaf Spot
  • Eyespot
  • Northern Corn Leaf Blight
  • Common Rust
  • Southern Rust
  • Southern Corn Leaf Blight
  • Goss’s Wilt and Leaf Blight Anthracnose Leaf Blight
  • Powdery Mildew
  • Stewart’s Wilt
  • Common Smut
  • Rhizoctonia
  • Other Common Corn Diseases – Other common diseases in corn include seed and seedling rots, also called pre- and postemergence damping-off. Some common fungal pathogens are Pythium and Fusarium.

Key Diseases in Soybeans

  • Septoria Leaf Spot (Brown Spot)
  • Frogeye Leaf Spot
  • Brown Leaf Spot
  • Asian Soybean Rust (Soybean Rust)
  • Powdery Mildew
  • Pod and Stem Blight
  • Sclerotinia Stem Rot (White Mold)
  • Sudden Death Syndrome (SDS)
  • Rhizoctonia
  • Late-Season Pytophthora Root Rot
  • Anthracnose
  • Brown Stem Rot
  • Other Common Soybean Diseases – Other common diseases include Cerospora blight, stem blights and stem rot.

Key Diseases in Cereals

  • Fusarium Head Blight
  • Leaf Rust
  • Powdery Mildew
  • Septoria Leaf Blotch
  • Net Blotch
  • Stagnonospora Glume Blotch
  • Tan Spot
  • Thielaviopsis (Black Root Rot)

Key Diseases in Cotton

  • Pythium
  • Rhizoctonia
  • Fusarium Wilt
  • Verticillium Wilt
  • Bacterial Blight
  • Target Spot (Corynespora cassiicola)
  • Cotton Root Rot

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