It is viral disease and transmitted by aphids, Melanaphis sacchari and Rhopalosiphum maidis, this virus is also spread by infected planting material. Dry weather conditions during October to until the end of harvest is favorable condition of this disease.
Symptoms
• The main diagnosis symptom is yellowing of the leaf midrib on the lower side in 3 to 6 leaves from the peak.
• The yellowing of mid rib and adjacent areas of laminar lost their primary colour are the sure and usual diagnostic symptoms.  
• In later stages, the yellowing may spread from midrib into leaf blade and yellowing of the leaves can be observed.
• The spindle axis dries along with the leaves in advance stage of the infection.