Crown Rot of Alfalfa
Symptoms:
- Brown areas develop in the crown tissue or root cortex
- Central core of crown and root may be rotted or hollow
- Plants become stunted
- Plants wilt and die
- Can cause considerable stand thinning and shortened stand life
Pathogen Involved:
- A complex of organisms is involved, the most common are fungi including Fusarium, Phoma, and Rhizoctonia species.
- Bacteria and nematodes can also be involved
Time of Occurrence:
- Severity and incidence of crown rot become greater as stand age increases
Conditions Favoring Disease:
- Poor fertility, low potassium in particular
- Other diseases can enhance crown rots
- Insect damage (clover root curculio and others)
- Low soil pH
- Damage to crowns from harvesting machinery and grazing animals
- Improper harvesting (too often or too late in the fall)
Disease Management:
- Minimize stresses and damage to alfalfa as noted under the section on conditions that favor disease
- Choose adapted cultivars for your area