Incidence and Distribution of Viruses Infecting Maize (Zea Mays L.) In South-Western Nigeria

Maize yield has greatly reduced in cultivated fields in many parts of south western Nigeria due to disease infection which has contributed immensely to the cost of production and economic loss to the farmers.A survey was conducted to investigate the incidence, distribution and severity of viral diseases on randomly selected farmer's cultivated maize field.Identification of the diseases was based on visual symptoms.Viral diseases incidence found on maize in the various farms was measured by calculating the percentage of plants showing viral disease symptoms in the maize population while the severity was assessed using a severity index scale of 1-5.Information recorded include the names of towns or villages in which survey was carried out, the coordinates of the farm (location) using the GPS (Global Positioning System), cropping system and other agronomic practices.Results were analyzed by one-way analysis of variance (ANOVA) using the statistical package for social sciences (SPSS) version 16.0.Means were separated where significant difference occur at p≤0.05.A simple regression analysis was used to test the effect of insect infestation on the severity of maize disease in the study area.The survey revealed that severity and incidence varied per location.Visible symptoms observed include; chlorotic patches, severe streaking, red pigments and venation along mid rib and vein and stunted growth.The incidence of the maize virus disease ranged between 10-37% while disease severity in the study area ranged between 3.25&1.50 in the entire farm surveyed.It was observed that cropping pattern had a positive correlation with disease incidence.Insect infestation in the study area ranged between 1.25-3.50.There was a positive correlation between disease severity and insect infestation, the higher the insect infestation, the higher the severity of the disease.There were variations in the insect incidence and disease severity in all the farm surveyed.Further research will provide a basis for high incidence of pest in cropping systems in the tropics.It is a thing to note that agricultural systems are designed to alter a given ecosystem.It is suggested that adequate crop protection practice should be applied in any cropping system.