Like other crops facing the challenge of pests and diseases, maize, Africa’s second most consumed cereal after rice is no exemption. Farmers in eastern Uganda have been battling the notorious Maize Lethal Necrosis Disease, also known simply as MLND, which causes low yields to total crop failure.
In 2013, several districts in the east were hit by MLND. Bulambuli, as a case in point, suffered a 30 per cent yield loss. When farmers spotted a “strange” disease, it was immediately reported to the Ministry of Agriculture and National Agricultural Research Organisation (Naro). Scientists at Naro took action by training farmers on preliminary methods to curb further spread.
Complied with measures
Farmers were asked to purchase maize seed from certified companies, burn plants with signs of MLND, planting seed saved from other farmers’ fields were discouraged, and about half a tonne of fake seed was impounded from input dealers. Most of the infected seed had been purchased from Kenya, so a ban was placed on maize seed from there.
Farmers were also advised to spray their plants with the recommended pesticides.
The farmers complied with the advice and suggested measures. The 2014 bumper maize harvest in all the affected districts is attributed to this. In Bulambuli District, up to 60,000 tonnes of maize were harvested in the first planting season. By the second season, few farmers reported the disease in their farms.
Alfred Tseketi, district agricultural officer, Bulambuli, explains what the farmers achieved was due to a concerted effort to curb the disease. As a result of the dry spell, the disease prevalence has reduced.
Peter Zerogoi, a farmer from Simu village, who owns more than 100 acres of land in Bwikonge Sub-county, is one of those who have had experiences with MLND. He planted maize on 60 acres and harvested 200 bags. To him, this is a loss because he is in position to obtain more than 800 bags.
“I usually get 15 bags per acre but in the last season, I harvested six bags per acre. I consulted Mr Tseketi, who advised me to burn the maize [stover] before ploughing and planting for the next season,” he said. However, Zerogoi complained about the low price of maize grain. A kilo in most markets in eastern Uganda is Shs400.
Beyond using the rudimentary preventive measures on farms, at the research level, there are efforts by scientists in East Africa to develop MLND-resistant varieties.
Kenya Agricultural Research Institute, with support from International Maize and Wheat Improvement Centre (CIMMYT) and Bill and Melinda Gates Foundation, has set up a breeding facility in Naivasha and Bomet to screen varieties. A trial of selected CIMMYT inbred lines showed several are highly resistant to the virus.
In Uganda, National Crops Resources Research Institute Namulonge is testing varieties acquired from Kenya and elsewhere at a number of trial sites. Dr Geoffrey Asea, head of the cereals programme, explains that with the outbreak of MNLD, scientists in East Africa started a collaborative regional research effort.
From this, the Namulonge team began breeding maize varieties for resistance and testing them for adaptation to various geographical conditions in multi-locational field trials. This is in collaboration with CIMMYT and Ohio State University.
According to Dr Asea, his team is in discussions with other scientists in the region with regard to using biotechnology to silence the virus. But this may take time to get to the farmers.
The scientists at Kenya Agricultural Research Organisation (KALRO) are of the view that, in the long run, deployment of varieties resistant to both Maize Chlorotic Mottle Virus (MCMV) and Sugarcane Mosaic Virus (SCMV) is the best means of managing MLND.
Through breeding, both conventional and transgenic maize seeds, resistance to MCMV can be incorporated into the susceptible varieties within a four-year period.
Dr Anne Wangai, chief research officer and MLND expert at KALRO, points out that the disease is spread by insects such beetles and thrips. “Upon feeding on infected plants, they pick the [virus] and transmit it to other crops they fly to or where the wind blows them.”
She adds that reports from other countries where the disease previously existed - such as US (Texas), Argentina and China indicate that transmission can also be through seeds but in very low rates of about 0.005 per cent.
Dr Asea states that early planting should be encouraged since pests tend to move from older to younger plants.
Field observations in Uganda showed that MLND infections were severe in farmer fields where maize was planted late. Therefore, farmers are advised to plant maize at the onset of the main rainy seasons and not during the short rain periods. This creates a break in planting seasons and reduces the populations of pests that spread MLND.
Maize lethal necrosis
Maize Lethal Necrosis Disease was first identified in farmers’ fields in US in 1976. It is caused by a combination of two viruses, namely Maize Chlorotic Mottle Virus (MCMV) and Sugarcane Mosaic Virus (SCMV), a pathogen prevalent in many parts of Kenya affecting cereal crops.
The double infection of MCMV and SCMV or any cereal viruses such as Maize Dwarf Mosaic Virus or Wheat Streak Mosaic Virus gives rise to MLND.
MLND, which has since spread in farmers’ fields in East Africa, was first spotted in the Western province of Kenya in 2011.
The disease quickly spread to Tanzania and eastern Uganda. In the districts of Busia, Sironko, Kapchrowa, Bulambuli, Manafwa, Bukedea and Mbale were most farmers concentrate in growing maize on large scale.
Symptoms of MLND include yellow patches on otherwise green maize leaves, dwarf plants and combs with very few or no grain fillings. Farmers are advised to immediately uproot infected plants to prevent further transmission.