Spring Black Stem and Leaf Spot
Symptoms:
- Dark brown to black spots on leaves and stems, usually with
fairly even color to border of lesion.
- Lesions often coalesce to form larger infected areas of leaves.
- Leaves turn yellow and tend to wilt before dropping.
- Leaves, stems, pods, and crowns can be affected.
- Can cause defoliation when weather is cool and wet, usually
most severe in lower part of the canopy.
Pathogen Involved:
- Phoma medicaginis (a fungus)
- Survives between crops on infested crop debris and on stems
and crowns
Time of Occurrence:
- Most common in spring and fall
- Often especially common in first cuttings
Conditions Favoring Disease:
- Cool and wet weather, especially when plants tall with high
density
Disease Management:
- No cultivars with high levels of resistance are available
- Early harvest can reduce disease development as well as yield
and quality losses.
Back to Alfalfa Diseases
|
