Efficacy of plant-based fungicide formulations on tomato late blight disease management in Tanzania

This study evaluated the effectiveness of plant-based fungicide formulations in managing tomato late blight (TLB), caused by Phytophthora infestans. Infected tomato leaves were collected from farmers’ fields in Karangai Village, Arumeru District, and used for pathogen isolation at the NM-AIST laboratory. In vitro trials identified two promising formulations: garlic extract combined with sunflower oil (GaSu₃) and sunflower oil combined with ginger extract (SuGi₃), which inhibited fungal colony growth to 2.8 ± 0.05% and 4.5 ± 0.07%, respectively, compared to the untreated control. These formulations were further evaluated in a screen house trial involving 10 treatments, including plant-based fungicides, synthetic fungicides applied at different intervals, and an untreated control. A completely randomized design (CRD) was employed with three replications, resulting in a total of 30 plots and 60 plants. The results revealed that all treatments experienced a 100% disease incidence; however, disease severity differed significantly (p ≤ 0.001). The highest proportion of uninfected fruits was observed in the synthetic fungicide treatments (96.3–99.3%), followed by the plant-based treatments (55.6–67.9%). The untreated control recorded the lowest proportion of uninfected fruits (48.4%). These findings indicate that although plant-based fungicides are less effective than synthetic fungicides, they significantly reduce disease severity and offer a viable, environmentally sustainable option for managing tomato late blight (TLB) in tomato production.