Periodic field surveys will reveal the presence and severity of foliar diseases. If excessive leaf drop occurs in the lower canopy, harvest the alfalfa as soon as possible to minimize further loss and reduce disease pressure. Root and crown diseases are of significant economic importance in Colorado because they can reduce plant vigor and lower winter survival rates. Over time, this decreases crop yields and shortens stand life. Once the plant has contracted a disease, there is no cure.
Genetic resistance is the best protection.
The pathogens responsible for root and crown diseases, such as bacterial wilt, fusarium wilt and phytophthora root rot, are prevalent in Colorado. Fortunately, most varieties have at least moderate resistance. Seedling diseases, such as seedling blight and damping off, can be problems if cool, wet weather persists over long periods during establishment. Fungicide seed treatments help reduce the incidence of seedling disease. While several Insects pests attack alfalfa in Colorado, the key problem is alfalfa weevil.