Integrated Disease Management of Tomato Early Blight: A Critical Narrative Review of Pathogen Complexity, Host Resistance and Sustainable Control

Abstract

Tomato early blight is a persistent foliar, stem and fruit disease problem whose management is complicated by pathogen diversity, polycyclic epidemics, quantitative host resistance and repeated reliance on fungicides. Historical literature often attributes the disease to Alternaria solani, whereas molecular taxonomic work increasingly shows that large-spored Alternaria associated with tomato can comprise A. linariae and other members of section Porri. This critical narrative review evaluates how that biological complexity changes the design of integrated disease management (IDM). Evidence was synthesised from peer-reviewed research and reviews on pathogen identity, epidemiology, host resistance, cultural and agronomic suppression, forecasting, fungicide performance and resistance, biological control, botanicals, induced resistance and nutrient-mediated approaches. The strongest evidence supports a layered strategy rather than substitution of one input for another. Accurate diagnosis and local epidemic knowledge establish the management context; resistant or less-susceptible cultivars reduce epidemic potential but rarely provide complete protection; canopy and residue management can reduce inoculum or favour less conducive microclimates; weather-based decision support can reduce unnecessary sprays when locally validated; and fungicides remain important in high-risk production but require mode-of-action stewardship because resistance has evolved in Alternaria populations. Biological agents, arbuscular mycorrhizal fungi, essential oils and host-priming approaches show credible activity, yet evidence is unevenly distributed between laboratory, greenhouse and field settings. Recent genomic and transcriptomic studies offer routes to improve quantitative resistance, while new process-based models may connect epidemiological forecasting with food-safety concerns. Major gaps concern species-resolved surveillance, multi-environment validation, durability and compatibility of non-chemical interventions, economic performance, and the scarcity of long-term field comparisons of complete IDM programmes. The most defensible management framework is therefore context-specific, resistance-aware and monitoring-led, combining preventive agronomy, host resistance, validated forecasting and judicious chemical or biological interventions.