The objective of this research project is to investigate and develop a potential non-phytotoxic, environmentally-friendly film-forming ACP repellent solution 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 14-A,B,C,D) were developed using a new EPA approved polymer and environmentally friendly silica source. Optimization process involved different ratios of polymer to silica. The objective was to have the best combination for formulation stability and rainfastness. A clay based commercial control (Surround WP) was used for comparison purposes and this product is available to growers. Safety analysis of OS-SG 14 series was conducted using sour orange citrus as a model plant. 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, 34oC). OS-SG 14 series did not cause any plant tissue damage at the applied rates, neither the Surround WP control. Temperature testing was conducted to determine if the presence of polymer posed a risk of increasing the heat build up on the plant surface. The OS-SG 14 series did not exhibit significant increases in temperature over commercial control. The composition and interactions between the components were confirmed using Fourier transform infrared spectroscopy (FT-IR), which confirmed the presence of silica from Si-O stretching, SiO-H stretching, Si-H bending and the polymer was detected from C=O stretching. The morphology of the new silica core used in OS-SG 14 series was observed using Scanning Electron Microscopy (SEM) and revealed large micron and sub-micron size irregular shaped particulates. The crystallinity of the silica core was studied using X-ray diffraction and it was found to be mostly amorphous with some crystalline structures. The commercial control material was amorphous in nature. The most optimized version from the OS-SG 14 series will undergo further studies including additional SEM, XRD and NMR characterizations. Film adherence (rainfastness) will be studied using AAS and atomic force microscopy (AFM). One or two best performing formulations will be selected from the from the OS-SG 14 series for future trials.