New model to control deadly maize disease

MLNMLN causes severe stunting, leaf necrosis and premature death for maize plants. (Image source: International Institute of Tropical Agriculture/Flickr)As maize lethal necrosis (MLN) causes up to 90 per cent production loss, the researchers is trying to figure effective ways to combat infectious viruses causing MLN in Kenya

With maize being the staple crop in the Sub-Saharan Africa, the spreading of the disease is affecting food security for people in the region.

Nik Cunniffe, co-author and lecturer in mathematical biology at the University of Cambridge, said that the objective of the study was to test the implementation of mathematical modelling in making practical recommendations for disease control.

In a statement to the SciDev.Net, Cunniffe commented, “This is important since MLN is a big problem, causing up to 90 per cent yield loss in heavily infected areas.” Apart from Kenya, where MLN has been spreading for the last six years, the disease has also been detected in Ethiopia, Rwanda and Tanzania, added Cunniffe to the source.

According to the UN Food and Agricultural Organisation (FAO), the MLN is a result of a combination of two viruses, the maize chlorotic mottle virus (MCMoV) and any of the cereal viruses in the Potyviridae group, like the sugarcane mosaic virus (SCMV), wheat streak mosaic virus (WSMV) or maize dwarf mosaic virus (MDMV). The double infection of the two viruses gives rise to MLN disease, which is also termed as corn lethal necrosis (CLN).

The researchers across France, Germany, the UK and the US modelled the spread of the viruses causing MLN to understand the dynamics of the disease within and between growing seasons of the crop. The model allows the transmission of the virus via vectors, soil and seeds, according to the study published in August 2017.

After that, the researchers reviewed the control strategies for large and small farms considering the scenarios of no management of disease, management without crop rotation and management with crop rotation.

According to the study, small and large farms differ in management strategies that each can adopt, with insecticide sprays and clean seed for large farms and rouging adopted by the small farms. The study did not consider the effect of maize varieties with MLN tolerance, because availability of locally adapted and agronomically acceptable and tolerant hybrids is limited.

The findings show that combining crop rotation, using virus-free seed, removing plants that show disease symptoms and controlling insect pests are the ways to control MLN. However, Cunniffe added that the control needs to be done synchronously in large areas to control other diseases that can repeatedly re-invade from outside the controlled area.

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