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Maize lethal necrosis disease

Distribution

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Host plants / species affected

Main hosts

show all species affected
Zea mays (maize)

List of symptoms / signs

Growing point - dead heart
Leaves - abnormal colours
Leaves - abnormal patterns
Leaves - necrotic areas
Leaves - yellowed or dead
Seeds - mould
Stems - dead heart
Stems - dieback
Stems - stunting or rosetting
Whole plant - dead heart
Whole plant - early senescence
Whole plant - plant dead; dieback

Symptoms

Maize chlorotic mottle virus (MCMV) causes a variety of symptoms in maize depending upon genotype, age of infection and environmental conditions. They range from a relatively mild chlorotic mottle to severe stunting, leaf necrosis, premature plant death, shortened male inflorescences with few spikes, and/or shortened, malformed, partially filled ears (Castillo and Herbert, 1974; Castillo Loayza, 1977Niblett and Caflin, 1978; Uyemoto et al., 1981).

When MCMV co-infects maize with a potyvirus, the infected plants in the field show a diverse range of symptoms. Diseased plants develop symptoms characteristic of virus diseases. There is chlorotic mottling of the leaves, usually starting from the base of the young leaves in the whorl and extending upwards toward the leaf tips. The leaves can experience necrosis at the leaf margins that progress to the mid-rib resulting in drying of the whole leaf. If there is necrosis of young leaves in the whorl before expansion, then 'dead heart' symptoms will be visible. Other symptoms include premature aging of the plants and mild to severe leaf mottling. Severely affected plants form small cobs with little or no grain set. The entire crop can frequently be killed before tasseling (Niblett and Claflin, 1978; Uyemotoet al., 1980, 1981; Wangai et al., 2012).

Prevention and control

Prevention

Seed Inspectors can check for Maize lethal necrosis disease (MLND) in seed farms. A plant health inspectorate organization can test for Maize chlorotic mottle virus (MCMV) in all seed coming into the country including the material for breeding. Domestic regulation can be put in place to prevent the movement of maize products from affected areas to disease-free regions.

The public can be informed about the disease through press releases, posters, brochures, sensitization workshops and radio programmes. Information on the disease could be passed on to the public during field days and Bazaras in churches. Awareness of the disease will help farmers to take it upon themselves to avoid the movement of diseased plant material from one area to another by destroying affected crops, rouging and practicing general field hygiene.

Control

The best approach for the management of MLND is to employ integrated pest management practices encompassing cultural control such as closed season, crop rotation and crop diversification, vector control using seed treatment followed by foliar sprays, and host-plant resistance.

Cultural Control and Sanitary Measures

Crop rotation can effectively control MCMV (Uyemoto, 1983). Producers are advised to practice crop rotation for at least two seasons with alternative non-cereal crops such as potatoes, sweet potatoes, cassava, beans, bulb onions, spring onions, vegetables and garlic. Planting different crops each season will diversify farm enterprises. Manure and basal/top dressing fertilizers can be applied to boost plant vigour.

It is necessary to use good field sanitation methods, including weed control measures to eliminate alternate hosts for potential vectors (Wangai et al., 2012b). Infected foliar material should be removed from the field to reduce pathogen and vector populations. This material can be fed to livestock, but grain and cobs that are rotten should not be fed to humans or animals. These should be destroyed by burning.

Seed should not be recycled; farmers should plant certified seed only.

To create a break in maize planting seasons, plant maize on the onset of the main rainy season and not during the short rain season. This will reduce the population of vectors.

Before MCMV had spread to other islands in Hawaii, it had been controlled for several years in the island of Kaua’i. (Nelson et al., 2011).

Movement Control

There is need to have regulation by governments to impose quarantine on the movement of maize materials from affected areas within a country. Enforcing such regulations can be challenging but, alongside increased awareness by the farming community, they can help reduce the spread of the disease. 

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


This information is part of a full datasheet available in the Crop Protection Compendium (CPC);www.cabi.org/cpc. For information on how to access the CPC, click here.