Lethal Nucresis (MLN) Maize Diseases And How To Manage It

Symptoms

• Rot on the leaves, usually starting from the base of the young leaves in the whorl (funnel) and extending upwards toward the leaf tips.
• Mild to severe leaf mottling.
• Premature aging of the plants.
• Necrosis of leaf margins that progress to the mid-rib, resulting in drying up of the whole leaf.
• Necrosis of young leaves in the whorl before expansion, leading to a ‘dead heart’ symptom and death of the plant. Even though maize is reported to be the primary host of the MLN disease, a wide range of plants in the grass family (73 species) could be possibly affected by this disease.

Cause of the disease

The disease is caused by co-infection with two viruses, the sugarcane mosaic virus (grouppotyviridae) and maize chlorotic mottle virus(MCMV) (group tombusviridae). The MCMVis a new virus that had not previously beenreported in Kenya.

Transmission of MCMV

The disease is reported to be spread by maize (corn) thrips, maize (corn) rootworms and leaf beetles.

Management

• Practise crop rotation for at least two seasons, with alternative non-cereal crops such as Irish potatoes, sweet potatoes, cassava, beans, bulb onions, spring onions, vegetables and garlic.
• Farmers should plant certified seed only and not recycle own seed.
• Diversification of farm enterprises by planting different crops each season.
• Remove infected foliar material from the field to reduce pathogen and vector population. This material can be fed to livestock.
• Grain and cobs that are rotten should not be fed to humans or animals. These are to be destroyed by burning.
• Use manure, basal, top dressing fertilisers to boost plant vigour.
• Plant maize at the onset of the main rainy season and not during the short rainy season so as to create a break in maize planting seasons. This will reduce the population of vectors.
• Use good field sanitation methods, including weed control measures to eliminate alternate hosts for potential vectors