Kentucky IPM Pest Information Pages
Lepto Leaf Spot
Symptoms
Plants with Lepto leaf spot will have tan leaf spots with brown borders, giving an "eyespot" appearance. Spots sometimes have a yellow margin. Leaves and stems eventually blight and turn tan. Spots may be evident in all but the very youngest leaves on growing shoots. This disease tends to be most severe in first or second cuttings.
The fungus Leptosphaerulina trifolii is the causal agent
of Lepto leaf spot. Development of the
disease is favored by cool, wet weather during alfalfa
regrowth. Disease pressure is often high
following freezing of alfalfa stems or in fields where a
cutting is left unharvested. This is because dead
alfalfa leaves and stems are often colonized by the fungus, which then produces spores that are spread to the healthy alfalfa.
The fungus survives in alfalfa residue.
Spores are spread by air currents and can also attack
clovers.
Cause
IPM Techniques