Maize lethal necrotic (MLN) disease was first identified in the USA in 1976 and referred to as corn lethal necrosis (CLN) disease. In USA (Kansas) CLN was reported to have caused maize yield losses in the range of 50 to 90% in the field. MLN is a result of interaction between two viruses infecting maize plant at the same time. One of them is Maize chlorotic mottle virus – MCMV (Machlomovirus: Tombusviridae) and the other one is a member of the genus Potyvirus, family Potyviridae, Sugarcane mosaic virus- SCMV or Maize dwarf mosaic virus - MDMV or Wheat streak mosaic virus - WSMV. In Kenya the infections rates and yield losses of up to 100% have been reported under server conditions.