Maize Lethal Necrosis Disease (MLND) is a condition in maize caused by a combination of viruses: Maize Chlorotic Mottle Virus (MCMV), Sugarcane Mosaic Virus (SCMV), Maize Dwarf Mosaic Virus (MDMV) and Wheat Streak Mosaic Virus (WSMV).
The pathogens of the diesease, which were first identified in the USA in 1976, are prevalent in many parts of Kenya and affect cereal crops.
The disease was first reported in Kenya in 2011 and later in Tanzania, Uganda, the DRC, among other countries in East and Central Africa.
MLND is a significant threat because it can result in a yield loss of up to 100%.
Maize Lethal Necrosis Disease evident on the leaves [Photo-Courtesy]
Transmission Modes of MLND
Maize thrips (Frankliniella williamsi), maize rootworms (Diabrotica undecimpunctata, Diabrotica longicornis, and Diabrotica virgifera), cereal leaf beetles (Oulema melanopus), corn flea beetles (Systena frontalis), and Chaetocnema pulicaria are mechanical vectors of MCMV.SCMV is spread by maize aphids.
Seeds produced from infected plants are also an effective way of transmitting the disease, apart from moving animals, people, and farming machinery, which all spread the disease.
Symptoms of MLND
Symptoms of Maize Lethal Necrosis Disease include:
1. Premature drying of husks
2. Severe leaf damage
3. Tussel sterility, which impedes pollen production
4. Cobs with little or no grain filling
5. Internodes that are too short (where the plant's leaves emerge)
6. Central shoot withering and drying (dead heart symptoms)
MLND can lead to 100 percent yield loss [Photo-Courtesy]
How to Prevent the Spread of MLND
MLND can be effectively controlled through these 12 important steps spearheaded by the International Maize and Wheat Improvement Center (CIMMYT):
1. Before planting, learn about the field's cropping and disease history.Practice crop rotation if necessary.
2. Ensure that the farm's soil is fertile at all times to ensure that crops are healthy enough to fight diease infections.
3. Use MLND-free certified seeds.
4. Do not use grains as seeds.
5. Clean farm tools and equipment using disinfectants before and after use to eliminate MLND contamination.
6. Plant early in the rainy season.
7. Maintain a clean farm by removing grass, weeds, and other alternative hosts in the field.
8. Monitor the field every week for the presence of insect vector populations. A high population increases the chances of an MLND attack.
9. Remember that chemical control of insect vectors can be done using recommended insecticides (once every 1-2 weeks).
10. Try to search weekly for MLND viral symptoms for early detection and control of insect vectors.
11. Remove MLND-symptomatic plants from the farm and dispose of them in a fire or bury them.Do not feed infected plants to livestock.
12. Practice crop rotation for at least one season by growing non-cereal crops, preferably legumes (soya, beans, and cow peas). Avoid continuous intercropping of maize. Ensure a closed maize season of at least two months where possible.
Source: International Maize and Wheat Improvement Center (CIMMYT)
- Written by Sam Oduor