Lepto Leaf Spot


  • This disease, also called pepper leaf spot, primarily affects young leaves.
  • Lesions begin as small brown spots that may develop into larger (1-3 mm) spots with a dark brown margin, and are often surrounded by a yellow halo.
  • Lesions can enlarge to kill patches on the leaves.
  • Leaflets may be killed and drop after clinging to the stems for some time.
  • More than one leaf disease often occurs at the same time on a plant.
  • Symptoms vary according to the rates of stem and leaf growth, and are influenced by humidity, temperature, and light intensity.

Pathogen Involved:

  • Leptosphaerulina briosiana (a fungus)
  • Overwinters on leaf and stem debris on soil surface

Time of Occurrence:

  • Most common in spring, early summer, and fall

Conditions Favoring Disease:

  • Cool and wet weather

Disease Management:

  • Most alfalfa cultivars have low levels of resistance, but some newer cultivars may express improved tolerance to leaf diseases.
  • Early harvest typically reduces disease development and the associated yield and quality losses.
  • Early harvest also helps reduce loss of infected leaves, resulting in a reduction of inoculum that could infect new growth.