Disease without borders: what we learnt from our fight against Maize Lethal Necrosis (MLN)

Masinde, Joshua (CIMMYT), Francis Mwatuni (CIMMYT) and Dr. Suresh,L.M. (CIMMYT ) :

Experts from research, plant health and seed sector organizations from eastern and southern Africa gathered in Nairobi on October 15-17, 2019, to reflect on the tremendous impact and lessons learned from the multi-pronged, transboundary coalition to contain the maize lethal necrosis (MLN) disease across the region. They called for continued efforts to fight this devastating viral disease and prepare African nations for future plant health threats.

It’s eight years since the maize lethal necrosis (MLN) disease was first reported on the African continent, in Kenya’s Bomet County in 2011. At the time, a sense of panic swept across the maize sector as this viral disease could wipe out maize fields with experts quickly realizing that all maize varieties on the market were susceptible to MLN.

Spearheaded by the International Maize and Wheat Improvement Center (CIMMYT), a rapid regional response involving national agriculture research systems (NARS), national plant protection organizations (NPPOs) and seed sector partners was set up. This involved multi-pronged approaches that included integrated rigorous surveillance, epidemiology research, disease management across the seed value chain, screening and fast-tracking of the MLN tolerant maize breeding program.

Reflecting on the tremendous impact of transboundary coalition to contain the devastating disease

“Country reports show there are now much less incidents of MLN in the region. We have effectively contained this disease as no new country in sub-Saharan Africa reported MLN since Ethiopia in 2014. This is a great of an effective public private partnership,” noted B.M. Prasanna, Director of CIMMYT’s Global Maize Program and the CGIAR Research Program on Maize.

He was speaking at the closure workshop for the USAID-funded MLN Diagnostics and Management and the Bill and Melinda Gates Foundation (BMGF)-funded MLN Epidemiology projects on October 15-17, 2019, in Nairobi.

“The outbreak of the disease in Uganda in 2012 was a huge challenge as all the maize varieties/hybrids on the market were susceptible. With the support of CIMMYT and other partners in the national agriculture research systems, we got access to Bazooka, a high-yielding, drought and MLN-tolerant maize variety that has helped in containing the disease,” said Godfrey Katwere, marketing manager for NASECO.

Till now, nineteen MLN tolerant and resistant hybrids have been released in sustaining efforts to keep the disease away from farmers’ fields and stopping its spillover to non-endemic countries in sub-Saharan Africa (SSA).

Science in action against the emerging disease

The MLN screening facility, established in Naivasha in 2013 thanks to funding from BMGF and the Syngenta Foundation for Sustainable Agriculture, has been key to a better understanding of the disease, its scope and for setting up the MLN hybrid tolerance and resistance breeding efforts. The facility has supported public and private partners to screen over 200,000 germplasm with around 300,000 rows of maize.

State-of-the-art epidemiology research has been carried out to identify how the disease could be transmitted and the best diagnostics methods along the seed value chain.

As part of the project, studies conducted by University of Minnesota Professor Benham Lockhart and Peg Redinbaugh a Professor at Ohio State University and Research Leader and Research Plant Molecular Geneticist at USDA, on the extent of MCMV transmission through the soil showed moist soil had higher virus loads than dry soil. The studies, which helped in understanding how the disease is transmitted and how to define management protocols, also indicated that MCMV can stay active in runoff water.

“Crop debris may also act as source of MCMV inoculum but for a limited period of up to 2 months, says L.M. Suresh, CIMMYT Maize Pathologist – Sub Saharan Africa in reference to soil transmission studies conducted by CIMMYT. “A host-free period of two months is, therefore, recommended for effective management of MLN,” he notes.

Rapid and low-cost MLN-causing virus detection methods such as immunostrips and ELISA-based tests were adopted at scale.

“After optimizing the protocols for MLN viruses’ diagnosis suitable for African systems, we transferred these technologies to NPPOs and seed companies not just within the endemic countries but also to the non-endemic countries in southern and west Africa through intensive trainings. We created a digital MLN surveillance tool under the Android Open Data Kit (ODK) app for NPPOs and other stakeholders to effectively carry out MLN surveillance on the ground. The survey information is captured in real time in farmers’ and seed production fields coupled with rapid immunostrips MLN tests,” Prasanna remarked.

According to Francis Mwatuni, Project Manager of the MLN Diagnostics and Management project, this proactive and collaborative surveillance network has been an important outcome that helped curb MLN from spreading to non-endemic regions. “In 2016, we only had 625 surveillance points. By 2019, the surveillance points in all the target countries stood at 2,442, which intensified the alertness on MLN presence and how to effectively deal with it,” he said. In total, 7,800 surveillance points were covered during the project implementation period.

Over 100 commercial seed firms have also been trained on how to produce MLN-free seed to facilitate trade within the endemic nations and to ensure the disease is not transferred to the non-endemic countries via contaminated seeds.

Sustaining the fight against MLN and preparing for the next potential threat

Surveillance work to lessen MLN’s resurgence or new outbreaks continue. In 2018, incidents in all endemic countries, except Ethiopia, declined sharply. One suggested explanation for the upsurge in Ethiopia, especially in the north western region, was a reduced pesticide use for fall armyworm (FAW) control as compared to previous years where heavy application of FAW-controlling pesticides also wiped out MLN insect vectors such as maize thrips and aphids.

With the culmination of the projects, partners from the implementing countries urged for scaling up the second-generation MLN tolerant and resistant varieties. Farmers would fully benefit from recent genetic gains of the new improved varieties and protected against this devastating disease.

“Despite the success registered, MLN is still a major disease requiring constant attention. We cannot rest as we redirect our energies at sustaining and building on the gains made,” said Beatrice Pallangyo, Principal Agricultural Officer in Tanzania’s Ministry of Agriculture, Food Security and Cooperative.

 With the fight against MLN rendered successful, stakeholders suggested the need to stay alert on other transboundary pests and diseases such as the tar spot complex, which could be a major threat to Africa’s food security in case of an outbreak.

Associated Scientists

B.M. Prasanna (Program Director); Francis Mwatuni (Project Manager), L.M. Suresh (Maize Pathologist – Sub Saharan Africa)

Research Team

Global Maize Program (GMP)

Funding Partners

The Bill & Melinda Gates Foundation (BMGF)

The United States Agency for International Development (USAID)

Syngenta Foundation for Sustainable Agriculture

 Technical Partners

International Institute of Tropical Agriculture (IITA), Alliance for a Green Revolution in Africa (AGRA), African Agricultural Technology Foundation (AATF), Ohio State University / USDA-ARS, University of Minnesota, USA, Seed companies, National Agriculture Research Systems (NARS) and the National Plant Protection Organizations (NPPOs) in project countries


Maize Lethal Necrosis (MLN) Diagnostics and Management project / Maize Lethal Necrosis (MLN) Epidemiology project


Africa / Ethiopia, Kenya, Malawi, Rwanda, Tanzania, Uganda, Zambia and Zimbabwe


Maize lethal Necrosis, Plant Health, Plant disease, Food Security, drought tolerant, climate change, partnership, pests and diseases

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