Integrated Management of Bacterial Fruit Blotch of Watermelon (Citrullus lanatus L.) Using Botanical Extracts and Varietal Selection in the Guinea Savannah of Taraba State, Nigeria

Abstract

Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, severely limits watermelon (Citrullus lanatus) production. Concerns about environmental pollution, pathogen resistance, and food safety associated with synthetic bactericides highlight the need for sustainable management alternatives. This study evaluated the combined effects of botanical extracts and varietal selection on BFB suppression and watermelon yield in the Guinea Savannah agroecological zone of Taraba State, Nigeria. Field experiments were conducted at Wukari and Ardo Kola during the 2020 and 2021 cropping seasons using a 4 × 5 factorial arrangement in a randomized complete block design with three replications. Four varieties—Sugar Baby, Charleston Gray, Crimson Sweet, and Kaolack—were evaluated under five treatments: neem (Azadirachta indica) extract, jatropha (Jatropha curcas) extract, combined neem and jatropha extracts, copper hydroxide, and an untreated control. Preplanting soil analyses characterized the experimental sites. Disease incidence, disease severity, infected fruit counts, growth parameters, and fruit yield were assessed. Data were analyzed using analysis of variance, with means separated by Duncan’s multiple range test at the 5% significance level; correlation and regression analyses examined relationships between disease parameters and yield. Both sites had slightly acidic sandy loam soils suitable for watermelon production. Varieties and management treatments differed significantly (P ≤ 0.05). Charleston Gray consistently exhibited the lowest disease incidence and severity and the highest yield, whereas Sugar Baby was the most susceptible variety. Combined neem and jatropha extracts significantly suppressed BFB and increased yield compared with the individual extracts, copper hydroxide, and the untreated control. Charleston Gray receiving the combined extracts achieved the greatest disease suppression and highest yield. Disease parameters were strongly positively correlated with one another and negatively correlated with yield. Disease severity explained approximately 81.5% of the variation in fruit yield. These findings support integrating Charleston Gray with combined neem and jatropha extracts to manage BFB and improve watermelon yield under the studied conditions, with potential to reduce reliance on synthetic bactericides.