Prevalence and Incidence of Major Fungal Diseases of Tomato (Solanum Lycopersicum L) In Kano and Kaduna States, Northern Nigeria

Abstract

Tomato (Solanum lycopersicum L.) is a major cash crop in Northern Nigeria, but fungal diseases are widely cited as a principal cause of the persistent gap between smallholder and research-station yields (Mohammed et al., 2023; Usman & Mohammed, 2023). Standardised, farm-level epidemiological data comparing disease burden between contrasting agroecological zones remain scarce. This study determined the prevalence and incidence of five major tomato fungal diseases across eight Local Government Areas (LGAs) in Kano and Kaduna States and compared disease burden descriptively between the two states. A total of 240 tomato farms (30 per LGA) were monitored biweekly over two consecutive growing seasons using standardised photographic field guides and pathologist-verified identification protocols (inter-rater κ ≥ 0.80). Early blight was the most prevalent disease overall, recorded on 86.7% of farms in Kano State and 79.3% in Kaduna State. Because between-state comparisons necessarily used LGA-level means (n = 4 per state) as the unit of analysis to avoid pseudo-replication across clustered farms, these comparisons are reported as descriptive, ecological-level patterns rather than confirmatory population-level tests: Kano State showed a consistently higher late blight burden (74.3% vs. 61.7% prevalence, 95% CI for the difference [9.7, 15.5]) while Kaduna State showed a consistently higher Fusarium wilt burden (73.3% vs. 57.7% prevalence, 95% CI for the difference [-18.7, -12.6]), patterns consistent with the irrigated-lowland versus cooler continuous-monoculture profiles of the two states. Baseline farmer disease-identification accuracy was only 41.0%, confirming that unaided visual diagnosis is insufficient to guide fungicide decisions (Balogun et al., 2023; Yakubu et al., 2024). These findings provide a standardised between-state epidemiological comparison for two leading tomato-producing states and support state-differentiated disease management guidance rather than uniform national recommendations, though confirmatory farm-level modelling is recommended before the between-state differences are treated as definitive.