Plant Health Initiative

Scouting for Soybean Viruses

Watch for possible virus infections in fields with moderate to high insect feeding, such as aphids. Photo credit: University of Wisconsin

To determine if a virus problem exists in your field, look for the following signs:

• Moderate to high insect activity
• Presence of leaf symptoms: mottled, crinkled leaf symptoms typical of virus infection.  Foliar symptoms of virus infection will be most apparent during times of rapid growth and cooler weather.
• Lower than expected yields
• Mottled seed
• Green stem plants at harvest maturity

Be aware that leaf symptoms are not a consistent indicator of virus infection. Soybean varieties differ in the amount of leaf symptoms that develop. Climatic conditions and growth stage can also mask leaf symptoms. Mottled and crinkled leaves can have other causes, such as herbicide injury or nutrient deficiencies.

Seed coat mottling is not a reliable symptom

Check seed at maturity for signs of discoloration and mottling. Seed infected with SMV and other viruses are often discolored.

Unfortunately, seed mottling is not a reliable indicator of SMV or BPMV infection because some varieties develop seed mottling when infected, but other varieties do not. Some virus-infected seeds do not have coat mottling symptoms. Sometimes mottling occurs in seed that is not infected with virus.