The Effect of Photocatalytic Titanium Dioxide and Ultraviolet B Radiation on Sclerotinia homoeocarpa Growth and Pathogenicity

Photocatalytic TiO₂ [titanium dioxide] generates strong oxidative effects when illuminated with ultraviolet (UV) light with wavelengths of less than 385 nm. UVB has wavelengths ranging from 280 to 315nm. Previous research indicates the oxidative species and UVB radiation can react and cause cellular damage to microorganisms, which may reduce Sclerotinia homoeocarpa growth and help to control dollar spot disease development. The objectives of this study were to investigate the interactions of TiO₂ and UVB radiation, both in vitro and in vivo, on the growth and development of dollar spot. Factorial treatments consisting of five rates of TiO₂ and three doses of UVB radiation were arranged in a completely random design. The in vitro study showed that the mycelia linear extension of S. homoeocarpa was significantly inhibited by UV radiation. The highest UVB radiation (0.2754mol·m⁻²·day⁻¹ [mol per square meter per day]) resulted in the least mycelium growth. Regression analysis predicted that 14 days after inoculation the mycelium diameter of plates exposed to the highest UVB radiation without TiO₂ would be 27mm; while the non-treated control was predicted to be 243mm. There were no significant differences among TiO₂ rates compared to the non-treated control. Results were similar in the in vivo study where creeping bentgrass (Agrostis stolonifera L) was grown in pots in a growth chamber, and exposed to three doses of UVB radiation for 12 hours per day and 4 rates of TiO₂. The lowest UVB radiation (0.04549 mol·m⁻²·day⁻¹) treatment resulted in the largest infected area (58mm in diameter). Medium and high UVB radiation doses (0.1064 mol·m⁻²·day⁻¹ and 0.5444 mol·m⁻²·day⁻¹, respectively) reduced the infected area to 40mm and 46mm 14 days after inoculation respectively. Overall, it appears that UVB radiation may be involved in regulating the overall size of S. homoeocarpa growth, and applications photocatalytic TiO₂ may result in an increase in disease due to its UV screening capability.