Spots may be tan, brown, or black, and may have yellow halos. Leaves fall off when infections are severe. These fungi survive in undecomposed leaf tissue on the soil surface. Spores are spread by air currents or rainsplash. Infections occur when leaves are wet with dew or rain.
Serious outbreaks can occur during extended periods of humid, wet weather.
Rotate away from forage legumes for at least two years. Some varieties may suffer less yield loss, but varieties with high levels of resistance are not available. Tan leaf spots with brown borders, giving an eyespot appearance. Spots sometimes have a yellow margin. Leaves and stems eventually blight and turn tan.