Incidence and Severity of Common Viral and Fungal Diseases of Dry Season Tomato Crop in a Southern Guinea Savannah Agro-Ecology

Abstract

The incidence and severity of common fungal and viral diseases affecting dry season tomato crop were determined on the tomato field of the Teaching and Research farm of the University of Ilorin, situated in the Southern Guinea savannah ecological zone of Nigeria. Seeds were sown in January in the nursery and seedlings were transplanted to the field, inJanuary 2005 and 2006 at the age of 4 weeks. The growth period of tomato was partitioned into three stages viz: seedling/vegetative stage (1), pre-flowering stage (2), and flowering/fruiting stage (3), during which the incidence of fungal, viral or mixed fungal and viral diseases wereinvestigated. The aim was to identify the relative prevalence of the disease categories for each growth stages. The results showed plants in the earliest stage of growth with the lowest rate of infection. Nevertheless, viral disease incidence was the significantly highest (22.7%) at this stage. The incidence of double infections increased gradually from the second growth stagereaching 29% in the third stage. Comparatively, infection with virus alone in the third stage was 28.5%, while fungus alone was 0. 59%. The highest disease severity was in plants that were mixed infected by the two categories of pathogens. Such plants had significant retardation ofgrowth (height and mean number of leaves/ leaflets) and yield attributes such as the number of fruits produced per plant compared to singly infected and apparently healthy plants.Keywords: Disease incidence, dry season, tomato, Southern Guinea savannah ecology