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 15 and OS-SG 16 were tested for their plant safety and surface coverage , along with material characterization using infrared spectroscopy. Testing of those formulations were compared to commercial control, Surround WP. Preliminary results for this testing revealed comparable, but no significant improvement over commercial control for surface coverage. With surface coverage being of paramount importance in preventing infection via ACP-leaf interaction, further material development was needed. During this current reporting period , a new formulation, OS-SG 17 is being developed to overcome the weaknesses found in previous versions of the material. A new, all natural EPA approved silica source (“Fumed Silica”) was used as a silica substrate to create a multi-layered silica gel matrix when combined with our previous silica composite. The hydrophobic nature of the “fumed silica” is expected to increase the surface coverage of the new OS-SG 17 composite. Different iterations of OS-SG 17 are being studied as controls using our previously used EPA approved polymer to improve stability, dispersion and rainfastness. This new formulation is expected to display high colloidal stability in aqueous solution, high surface coverage and moderate rain-fastness properties. It was characterized using UV-Vis and FTIR spectroscopy. The colloidal stability of the formulation was checked via measuring %Transmittance (%T) of the supernatant collected from the solution left undisturbed. The formulation revealed less than 50 % transmittance up to 8+ hours which was found to be better compare to commercial control -Surround WP. Testing of this new version is in progress to ascertain the extent of its surface coverage and confirm that it does not create an unfavorable temperature increase on leaf surfaces. 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, 32 Celsius). OS-SG 17 formulation did not cause any plant tissue damage at the applied rates, matching the commercial control. Next we will conduct ACP repellent studies using psyllid containment cages which have been acquired recently.