Managing Alfalfa Diseases

Diseases of alfalfa can limit productivity of this valuable forage crop. Alfalfa diseases can reduce forage yield, reduce forage quality, and decrease stand persistence. The effects of diseases can be dramatic, such as sudden stand loss due to Sclerotinia crown and stem rot. Often, the effects of alfalfa diseases are more subtle but are no less important. For example, alfalfa plants with Phytophthora root rot sometimes regrow slowly after cutting, resulting in a stunted stand showing no other obvious symptoms of disease. Like most crop diseases, alfalfa diseases are most effectively managed by integrating as many control measures as practical. This report will provide an overview of several timely topics relative to alfalfa disease management

A Solution to Some Spring-Seeded Alfalfa Problems

One of the most important assignments I received when I assumed this position in 1990 was to address the question, What is the cause of seeding failure when alfalfa is spring-seeded into soils that remain wet after seeding? Six years of laboratory and field work have finally borne fruit. Based on our research, we can confidently present Kentucky alfalfa producers with three conclusions and a recommendation

Is Ridomil Recommended When Seeding Alfalfa?

Ridomil 2E® fungicide received a federal label in 1991 for control of seedling diseases of alfalfa caused by Pythium and Phytophthora fungi. Pythium fungi are widespread in Kentucky soils but can be controlled with Apron® seed treatment. Phytophthora is less common in Kentucky soils. Where present, Phytophthora can usually be controlled with a combination of resistant varieties and Apron seed treatment. Occasionally, yield increases may be observed using Ridomil in fields highly infested with Phytophthora. However, broadcast applications of Ridomil at seeding are not recommended for most alfalfa fields in Kentucky

Alfalfa Disease Management

Alfalfa can be a vigorous and productive forage crop for Kentucky farmers. Like all farm crops, however, alfalfa is subject to infectious diseases that can limit forage production. Managing these diseases is an important part of economical alfalfa production

Progress towards Sclerotinia--Resistant Varieties

Sclerotinia crown and stem rot (SCSR), caused by the fungus Sclerotinia trifoliorum, is one of the most important factors limiting the success of late-summer alfalfa seedings in the region. Infections of S. trifoliorum that progress into the crown of a fall-sown alfalfa plant can kill it during winter or spring green up. Stand losses by the following spring may be insignificant (1-3%) or nearly total, with 95-99% of the stand being dead (and often even rotted away and gone by spring green-up)