Pod and Stem Blight
Symptoms:
- The pathogen can infect all aerial parts of plants, but does not cause distinct lesions.
- The pathogen may be present in green tissue without causing symptoms, and signs of infection appear as plants mature.
- A key sign of infection is many, small, black, raised dots that are arranged in straight rows on the mature stem, and may be scattered on the pods.
- They also occur earlier in the season on fallen petioles.
- Infected seed are cracked, shriveled, dull, and may have a white mold on them.
- This diseases can cause significant yield losses and reduce seed quality.
Pathogen Involved:
- Diaporthe phaseolorum var. sojae (a fungus).
- This fungus overwinters in soybean tissue and in infected seeds.
Time of Occurrence:
- Infection can occur throughout the season, but signs of infection appear on fallen petioles in mid-season and on pods and stems of plants nearing maturity.
Conditions Favoring Disease:
- Wet, warm humid conditions and continuous soybeans.
Disease Management:
- Harvest seed quickly after it matures.
- Some varieties may differ in resistance to this disease.
- Rotate away from soybean.
- Plant high quality seed that is not infected with this pathogen.
- Foliar fungicides may be of value under conditions that favor severe disease.