Maize Lethal Necrosis: Impact and Disease Management

Abstract

The authors summarise and explore maize lethal necrosis (MLN) global impact, its causal viruses, their vectors, and disease management strategies. MLN is a destructive synergistic virus disease of maize caused by maize chlorotic mottle virus (MCMV) in combination with one of several viruses in the Potyviridae family. MLN causes severe chlorosis, necrosis, and eventual plant death, instigating severe yield losses. The causal viruses of MLN are mostly transmitted between plants by arthropod vectors, but they can also be transmitted at low frequency through seed and soil. Effective MLN management approaches include developing and growing maize with improved tolerance, crop rotation, controlling arthropod vector populations, managing disease reservoirs, and reducing disease transmission and spread through seed and soil. Despite the devastating impact of MLN over the past decade, especially in East Africa, tremendous progress has been achieved towards successful disease management. The rapid development and deployment of MLN tolerant maize in East Africa has proven an extremely effective management strategy, despite continuous maize plantings and the extensive presence of "green bridges". Identifying and stacking additional sources of MLN tolerance is desirable for breeding durable resistance. In the U.S., weed and vector management combined with crop rotation has effectively prevented the spread of MLN beyond a few states in the Midwest. However, it is important to consider the potential impact of climate change and the presence of pesticide/Bt resistant MLN insect vectors, which may facilitate greater vector proliferation and virus spread. Continued vigilance geared towards preventing virus or vector introduction to new locations is desirable, especially in tropical climates where multiple growing seasons occur annually. Fortunately, conditions conducive to an MLN epidemic are complex, requiring the presence of multiple maize infecting viruses and their respective vectors. Thus, several combinations of the disease management strategies discussed above are effective at managing the disease.