Seedling Diseases in Alfalfa
Seedling Diseases
Symptoms
Seedling diseases sometimes occur during periods of high rainfall in fields with soil compaction or other causes of poor drainage. Aboveground, plants appear stunted and yellowed, and may be wilted. In case of a Phytophthora infection, leaves sometimes also exhibit reddening. Belowground, roots and nodules appear decayed. Fungal infection of roots and stems of very young seedlings can cause sudden wilting and collapse (damping-off) of seedlings. Seedlings that are several weeks old at the time of root infection may become stunted or even killed, but still remain erect (seedling blight).
Cause
Seedling diseases of alfalfa in Kentucky are usually caused by Pythium, Phytophthora, Aphanomyces or Rhizoctonia fungi. Most of these fungi are common in Kentucky soils. Crop rotation does little to reduce their populations. Generally they do not limit stands of alfalfa seedlings, but can do so during periods of high soil moisture. Samples of dying plants should be sent to one of the University of Kentucky Diagnostic Labs for accurate determination of the fungi involved.
IPM Techniques
- Select well-drained fields.
- Prepare a fine but firm seedbed if seeding using conventional tillage.
- Use high-quality apron-treated seed of adapted varieties.
- Plant varieties with an R (resistant) or HR (highly resistant) rating to Aphanomyces for all spring seedings.
References and Additional Information
- IPM-1 Kentucky IPM Manual for Alfalfa
- PPA-10d Kentucky Plant Disease Management Guide for Forage Legumes by P. Vincelli, Extension Plant Pathologist, University of Kentucky
- PPFS-AG-F-3 Common Alfalfa Seedling Diseases and Disorders by Paul Vincelli, Department of Plant Patholody and Jimmy Henning, Department of Agronomy, University of Kentucky
- ID-104 Managing Diseases of Alfalfa by Paul Vincelli, Department of Plant Pathology, Garry D. Lacefield and Jimmy C. Henning, Department of Agronomy, University of Kentucky
- Compendium of Alfalfa Diseases. 2nd ed. Stuteville, D.L. & D. C. Erwin, (eds.) 1990.
