Several programmes have been initiated for the development of maize varieties with resistance traits of Maize streak virus (MSV) by International Institute of Tropical Agriculture (IITA), Ibadan, and have been released to farmers and research scientists. Therefore, a survey was conducted in five states in the south west of Nigeria (Oyo, Ogun, Ondo, Ekiti and Osun) during the raining planting season to determine the incidence of MSV disease by visual examination and serodiagnostic screening of symptomatic plants. The determination of infection rate of MSV disease by Cicadulina triangular on maize plant and its distribution from the lowest diseased leaf was also studied. The mean MSV disease incidence observed in these states was 35.95% which confirms the presence of MSV in the south west of Nigeria. Sero-diagnostic screening of virus-induced symptomatic leaf samples indicated that out of the 250 leaves sampled per state, 24.4% tested positive for MSV in Oyo, 25.6% in Ondo, 34% in Ogun, 19.6% in Ekiti and 38.8% in Osun. In two-week-old plants, symptoms developed on the leaves that were emerging at the time of inoculation, while in six-week-old plants, symptoms developed on the leaves directly below the emerging leaves irrespective of the number of C. triangular used. These suggest that the lowermost leaf with symptoms of the disease indicates the growth stage at which a plant was infected. There was a relationship between symptom expression and plant age which could be very effective when carrying out surveys to gather information for epidemiological studies. In addition, the 10 varieties of maize inoculated with MSV through C. triangular transmission showed no significant difference in disease severity over time irrespective of the number of C. triangular used.