Although birdsfoot trefoil is more persistent, this is due to the emergence of new plants from self-seeding, not longevity of original plants in a seeding. Diseases that cause problems in birdsfoot trefoil include crown and root rots caused by Fusariumspp. and other fungal pathogens, Stemphylium leaf spot, stem cankers and Fusarium wilt. There are a limited number of birdsfoot trefoil varieties available, and disease resistance remains a challenge. Pardee, a variety developed in Pennsylvania, has greatly improved disease resistance, but lacks adequate winter hardiness for Michigan conditions. To manage disease in birdsfoot trefoil, avoid rapid and complete defoliation (leave some leafy stems at harvest), allow reseeding, avoid stockpiling past early bloom, avoid excessive shading by grasses, and allow plants to rest in fall (September – mid October).
Control measures should be based on proper identification of disease, economic factors, and the effect of the growing environment. Walking your hay fields and pastures is essential to closely monitor disease and other plant development issues.
Spraying to control fungal diseases in forage crops is not a common practice in Michigan. If fungicides are considered, growers must pay close attention to the efficacy of the fungicide, pre-harvest intervals (within a cutting, and season-long), and application rates. For example, Ridomil Gold (mefenoxam) applied as a broadcast soil surface spray at planting is labeled for clover and birdsfoot trefoil to control damping off caused by Pythium spp. and root rot caused by Phytophthora spp. Fungicide seed treatments such as Apron XL (mefenoxam) are more common and should be used if seedling rots have resulted in poor stands in past years.
Source: Jim Isleib, Michigan State University Extension