Aim: The aim of the present study was to synthesize a castor oil-based matrix (COBM) for preparing a castor oil-based agro-formulation with cartap hydrochloride for controlling Xanthomonas oryzae, a rice pathogen. Methodology: Physio-chemical analysis of castor oil and constituents of fatty acid methyl esters were carried out by standard methods. Castor oil base matrix, with standardised ratio of oil: alkyl polyglucoside emulsifier (Simulgreen), was first synthesised, then ultrasonicated for size reduction and further tested for its stability. It was also characterised by thermal analysis and by optical microscopy. This base matrix and cartap hydrochloride were used to prepare an agro formulation. The activity of this agro formulation, against Xanthomonas oryzae (GenBank Accession number-VITXO MK547277.1), previously isolated from an agricultural paddy field in Vellore district (12.9165°N, 79.1325°E), was studied by well diffusion method using standard protocols. Results: Physio-chemical analysis revealed favourable characteristics for castor oil. Thermal analysis and optical polarised microscopic studies showed the presence of liquid crystals in the formulated base matrix. Its agro-formulation with cartap hydrochloride showed 22 mm zone of inhibition against the isolated Xanthomonas oryzae. However, aqueous solution of cartap hydrochloride showed a 13 mm zone of inhibition only, when tested at a similar concentration (2000 ppm), by well diffusion studies. Interpretation: The liquid crystal containing base matrix facilitated slow and sustained release of cartap hydrochloride from the castor oil-based agroformulation to achieve good activity against Xanthomonas oryzae. © Triveni Enterprises.