How to prevent common diseases in lucerne


Leaf spot

Leaf spot is a fungal disease in lucerne, and several types can be distinguished: common leaf spot, pepper leaf spot, downy mildew, rust etc. Usually leaf spot doesn’t cause serious economic losses, but it can lead to reduced growth and leaf losses. It appears most likely in warm, humid weather. When severe damage, the best measure is to harvest the crop. Quality might be lower.

Leaf spot lucerne

Wilt diseases

Wilt diseases are caused by pathogens (bacteria or fungi) that invade the vascular system of plants in warm seasons. This leads to plant wilting and usually dying. There are several wilt diseases:

  • Bacterial wilt (Clavibacter ssp.) - The top of the stems will wilt and the leaves will become yellow. It can be avoided by using an extended crop rotation and choosing the right variety (USA varieties are resistant, but they carry the disease with them onto the farm).
  • Verticilium wilt - Symptoms begin as temporary wilting of upper leaves on warm days. Appears in older stands and can give yield reductions up to 50%. As Verticilium is evaluated on varieties on the French recommended list, resistant varieties (Bardine, Alexis) can be picked.
Wilt diseases

Crown and stem rot

  • Anthracnose - This fungal disease starts with lesions on the stem, after which upper part of stem dies off. Because this can happen suddenly, dead leaves remain attached to the stem. Anthracnose happens most frequently in older stands, under hot and humid conditions in late summer. The use of resistant varieties, like Artemis or Alexis, is the only way to control Anthracnose.
  • Sclerotinia - This is caused by the Sclerotinia fungus and appears usually under cool, humid conditions, usually in young stands. It can be recognized by its white mycelia on the crown and stems, and by the presence of black hard structures. There is no genetic resistance, so Sclerotinia should be controlled by management. The removal of all leaves before winter and strict weed control is necessary to make sure air and sunlight can reach the bases of plants. This reduces the chance of fungal growth.
  • Rhizoctonia – A very common disease in arable crops like sugar beets. Affected plants are stunted, and the upper part of the roots is black and rotten. In lucerne it can appear after frost damage, poor drainage, heavy grazing or low fertility.
Crown and stem rot lucerne

Nematodes of lucerne

Nematodes of lucerne

Nematodes or roundworms that feed on plants are commonly called eelworms. These tiny worms can seriously damage your crops. The plant responds to the parasitic worms with swelling, distorted growth, and dead areas. Nematodes can also carry viruses and bacterial diseases inject them into plants.

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