Instead, use annual forage grasses or grain crops or, perhaps, perennial grasses, in rotations. Avoid using legumes in the rotation to reduce yearly re-inoculation of the field. Avoid planting alfalfa in the fall in fields with a history of clover or alfalfa or in fields adjacent to established alfalfa fields. The chances of having sclerotinia crown rot infection appears to be much higher in such circumstances. It appears that fall-seeded alfalfa is damaged most seriously in the early seedling stage.
Mature plants are more tolerant than seedlings.
Pre-emergence herbicides can reduce weed problems during establishment. Researchers applied fungicides in the fall in an effort to protect the seedlings in the critical stage. The experiment was unsuccessful but will be repeated with modification in the future. Copyright 1999 University of Missouri. Published by University Extension , University of Missouri-Columbia.