The objective of this research project is to develop and study a potential non-phytotoxic, environmentally-friendly film-forming ACP repellent material for preventing HLB infection. In the last reporting period, OS-SG 11, 12 and 13 were studied for plant safety and rainfastness and these formulations were delivered to our collaborators for ACP infection trials. In this reporting period, a new series of formulations OS-SG 15 were developed using an EPA approved polymer, dispersant (EPA approved “for food use” only) and clay source (EPK clay, local supplier). This version of material is intentionally developed to have a fair comparison with an existing commercial product (Surround WP; as proposed to be used as control). Optimization process involved adjusting ratios of different components (dispersant, polymer and silica-alumina) to have best combination of formulations to achieve high colloidal stability in aqueous solution and high leaf surface coverage for foliar application. The material characterization was done using Fourier Transform Infra-Red (FT-IR) spectroscopy. FT-IR spectra suggested interaction between the EPK particulate with other ingredients (polymer and dispersant materials). The colloidal dispersity in aqueous solution of formulations was measured using UV-VIS transmittance technique and the measurements were done at different time intervals. High colloidal dispersity was achieved up to 4 hours which was comparable/improved compared to Surround WP control. Safety analysis and plant leaf surface coverage of OS-SG 15 formulations were conducted using Cleopatra orange (common citrus variety) as a model plant. The formulations were sprayed at the application rate of 0.5 lbs/gallon (recommended rate for the commercial control). Phytotoxicity studies were conducted using a Panasonic Environmental Test Chamber (Model MLR- 352H) to control light intensity, humidity and temperature cycling to simulate summer conditions (85% RH, 34 degree C). The formulations revealed high plant leaf surface coverage at the application rate which was comparable to the commercial control. OS-SG 15 series did not cause any plant tissue damage at the applied rates, neither the commercial control. Temperature testing was conducted to determine if the presence of polymer posed a risk of increasing the heat buildup on the plant surface. The OS-SG 15 series did not exhibit any significant increase in temperature over the commercial control. Film adherence (rainfastness) will be studied using AAS and atomic force microscopy (AFM). From the OS-SG 15 series, one or two best performing formulations will be delivered for the ACP trial.