On-farm Validation of Coffee arabica and Aloe vera Extracts for Management of Seed-Borne Bacterial Leaf Spot Disease of Tomato

In Tanzania, seed infection by bacterial leaf spot (BLS) pathogens (Xanthomonads) causes yield losses up to 45% in the tomato ( Lycopersicon esculentum L.; Solanaceae family). Several studies have been conducted and wedged ecological organic agriculture (EOA) technologies (i.e., on botanicals/ biopesticides) which are significant to organic farmers in Tanzania. Nevertheless, these studies have been conducted in laboratory and screenhouse conditions, hence the technology cannot be disseminated to organic farmers for application before being validated. The current study was laid out as a 2x3 factorial experiment with five replications. Factor A was two common tomato cultivars “Rio grande” and “Malkia F1”, while factor B was seed treatment with three levels of crude plant extracts namely A. vera, C. arabica, and A. vera + C. arabica, and untreated control. Tomato seeds were soaked in the ready-made extracts for 12 hrs, then air-dried for 1 hr before sowing. The collected data were subjected to analysis of variance using Genstat 16 th edition software and means were separated using Tukey’s Honest Test at (α = 0.05). The highest efficacy against the pathogen ( Xanthomonas perforans ) causing bacterial leaf spot (BLS) was obtained from a combination of extracts from A. vera + C. arabica hence, recommended for seed treatment. Organic tomato farmers need to adopt seed treatment practices that ensure seedlings’ start-up and enhance crop growth and productivity. Although the results of validation comply with the recommendations from previous research findings, further study is needed to evaluate the effectiveness of plant extracts subject to seasonal variability among the production areas. Also, the bioactive fractions from the plant extracts and their mechanisms of action need to be evaluated comprehensively.