What Is Wrong With My Alfalfa Field?

Are there any yellow-green mottling of the leaves, plants may be stunted?

Are there any large diamond-shaped lesions with white centers on the lower portion of stems?

Are there any small circular brown-black spots with uneven margins on leaves?

Are there any white downy growths on the underside of the leaves, foliage may be yellow?

Are there any wilting shoots followed by bleaching of leaves and stem, and rapid wilting of stems on only one side of plant?

Are there dead plants scattered around the field, plants are stunted with small leaves and stems?

Do the seedlings fail to emerge or do they have light brown water-soaked roots and stems?

Are the plants defoliated, yellow-orange to white butterflies, and/or bright green larvae are present?

Are the leaves skeletonized and appear bronzed?

Are the leaves curled and yellow?

Are there singular, or closely grouped circular to irregularly shaped holes in the foliage?

Are the stems girdled causing part of the plant to above to break and turn red, purple, or yellow?

Alfalfa mosaic virus is transmitted by aphids. There is no known cure for viral diseases. Prevent problems by planting resistant cultivars, controlling aphids, and using virus-free seed from a reputable nursery.

Disease Anthracnose in alfalfa is caused by a fungus Colletotrichum trifolii. Young dead shoots take on a characteristic "shepherds crook" appearance. This disease is common in warm weather and periods of high moisture. It cannot be managed in established alfalfa stands. Cut crop before major losses occur.

Common leaf spot is caused by a fungus Pseudopeziza medicaginis. This disease is common in warm weather and periods of high moisture. Harvest infected alfalfa early to avoid severe infections which reduce hay quality. Rotating crops may reduce the incidence of disease.

Leaves and stems infected with fungal disease, Downy mildew, have spots covered with white fuzzy growth on the undersides. Cut alfalfa crop while still in the pre-bloom stage. Sow crop in spring to reduce the chance of seedlings becoming infected.

Fusarium wilt is a fungal disease that causes these symptoms in alfalfa. High soil temperatures favor the disease emergence. There is no satisfactory method of controlling this disease once it infects alfalfa. Prevent problems by planting resistant varieties.

Bacterial wilt causes these symptoms. It can be diagnosed by plants that are wilting during the day and recover at night. This disease occurs wherever alfalfa is grown, and it is one of the most important diseases in the US. Resistant cultivars are the only method of management.

Damping-off is a disease caused by several fungi. This disease occurs more often in cold temperatures when the growth of seedlings is slow and in moist soil. Treating seeds with fungicide before planting will give some control.

Alfalfa caterpillar consume entire leaves, including the midrib. Larvae have a white stripe running down the side of their body. Damage is most severe when eggs are laid in recently cut fields. Avoid unnecessary applications of insecticides to promote populations of natural enemies. Organically grown alfalfa can be treated with BTK (Bacillus thuringiensis). Harvest crops early to avoid serious damage.

Alfalfa weevils are known to skeletonize alfalfas leaves. Cutting the crop before budding is organically acceptable and can prevent serious damage and kill off most weevils. Other control methods include the application of insecticides.

Distorted, curled leaves are caused by aphids. These tiny insects cluster under leaves and on growing tips where they feed on plant sap. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Beet armyworm causes irregularly shaped holes in the foliage. Organic methods of controlling armyworms include biological control by natural enemies that parasitize the larvae and the application of BTK spray (Bacillus thuringiensis).

Three-cornered alfalfa hopper is a green, wedge-shaped insect. This insect is also a pest of other plants like soybean. It may be 3-4 generations of insects per year. Applications of appropriate insecticide are the preferred control method if insect becomes problematic.

Alfalfa is susceptible to several fungal root or stem rots. If the roots or stems have rotted your plants most likely suffered from these diseases. Root and stem rots are prevalent in water-saturated soil. Try to improve drainage if the soil tends to be waterlogged. Some cultivars are more resistant to rots, so plant them to prevent problems.