Infectious diseases contribute significantly to the death of alfalfa plants over the winter dormant period. Management of alfalfa diseases in New York does not involve chemicals, except for limited use of fungicidal seed treatment, but relies instead on sound crop management and the use of varieties resistant to a few serious diseases. Check with your local Cornell Cooperative Extension office for recent fact sheets and other information available to aid in identification and control of forage legume diseases. Vascular Wilts Vascular wilt diseases pose the greatest threat to alfalfa yields. This prevents water and nutrients from moving into the shoots, and the plants wilt and eventually die.
Varietal resistance is the single most important means of controlling vascular wilts.
The bacterial wilt pathogen is endemic in New York soils, and all adapted varieties need to possess a high level of bacterial wilt resistance. Recent evidence indicates that Fusarium wilt may also be a problem in the state, but the need for resistance has not yet been established. Many pathogenic microorganisms cause disease in alfalfa by attacking the roots, crowns, or lower portions of the stem. Phytophthora root rot causes significant losses during seedling establishment in wet, poorly drained soils. It can be controlled by a combination of strategies that includes selecting an appropriate site, planting resistant varieties, and following sound management practices.