Maize lethal necrosis (MLN) is a major disease affecting maize yields in eastern Uganda, causing 50-100% reductions. It results from infection by two viruses spread by insect vectors. A 2014 survey of 300 farmers in seven affected districts revealed farmers first encountered MLN in 2013, with average yield losses of 1.4 tons per hectare. Symptoms included chlorosis, stunted growth, and sterility. The disease was most destructive in the second growing season and continued increasing. Mitigation efforts focused on rogue plant removal, insecticides, fertilizer, crop rotation, and developing resistant varieties. Breeding programs obtained 30 resistant inbred lines being used to develop adapted genotypes for Uganda. Challenges included lack

1. Background
Maize lethal necrosis (MLN) is currently the leading cause of low maize yield in eastern
Africa. The MLN has so far been associated with 50-100% reduction in yield (ASARECA,
2013). The disease results from combined infection by two viruses: maize chlorotic mottle
virus (MCMV) and either maize dwarf mosaic virus or wheat streak mosaic virus (CIMMYT,
2004). The disease is spread by vectors, namely maize thrips, rootworms and leaf beetles.
Materials and methods
A baseline survey involving 300 respondents was conducted in seven most affected
districts of eastern Uganda in the year 2014, namely in Tororo, Busia, Mbale, Sironko
(including Bulambuli), Iganga, Kapchorwa and Bukwo.
The following facts were revealed about the MLN disease in eastern Uganda
- Most farmers in eastern Uganda first encountered MLN in 2013A (March to June).
- Grain yield loss as a result of the MLN in eastern Uganda in 2013 was 1.4 t ha
-1
.
- Most affected districts were Tororo, Mbale, Bulambuli, Sironko and Busia (Fig. 1).
- Key MLN symptoms were chlorosis, stuntedness, dead heart and necrosis, mottling of
leaves, and sterility or poor grain fill.
- The disease is more destructive in the second season (August to November).
- The disease is still on the increase in eastern Uganda
- Disease symptoms observed as early as two weeks after crop emergence.
- Yield loss ranged from 31-70%.
- Farmers who planted variety H513 from Kenya, were the most affected by MLN.
Fig. 2: An abandoned maize field due to high MLN in Nabongo Subcounty, Bulambuli District
MLN mitigation measures being undertaken
Sensitization efforts are being taken with emphasis on the following:
- Roguing and burning infected plants
- Insecticide sprays where it is economically viable
- Fertilizer boosts
- Crop rotation with non-cereal crops for at least two seasons
- Use of certified seed and avoid recycling seed
Breeding initiatives so far
About 30 MLN resistant inbred lines have been obtained from CIMMYT Kenya. Together with
lines from the National Program in Uganda, Kenya, CIMMYT Ethiopia and Mexico, we are in the
process of introgressing MLN resistant genes into adapted maize genotypes both for the low
and high altitude areas of Uganda.
Challenges
- No MLN screening facility in Uganda
- MLN resistant genes mostly in the yellow maize, which are not popular in East Africa
- The disease is sporadic.
REF: Kagoda et al. 2016. Status of MLN in eastern Uganda. African Journal of Agricultural
Research.
THE MLN EPIDEMIC AND APPROACHES TO MINIMISE LOSSES IN EASTERN UGANDA
Kagoda1
, F., R. Gidoi1
, A. Wasukira1
, G.E. Eneku1
and B. E. Isabirye2
1
Buginyanya Zonal Research and Development Institute, P.O. Box 1356, Mbale.
2
Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) Uganda
Contacts of corresponding Author: E-mail: fkagoda@gmail.com. Tel. +256772898988
Acknowledgements: Government of Uganda for funding, Local Government officials, particularly the District Agricultural Officers of Sironko, Bulambuli, Mbale, Kapchorwa, Iganga, Busia and Tororo
Fig. 1: Districts with
highest MLN severity
scores (nm) in eastern
Uganda